CA1187324A - Tar-depleted liquid smoke treatment of food casings - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A tar-containing aqueous liquid wood smoke is extracted with selected organic liquid solvents to form a tar-enriched liquid fraction and a tar-depleted aqueous liquid smoke fraction, the latter being used for food casing treatment to facilitate smoke coloring and flavoring of encased foodstuff during processing.

Description

TAR -DE:PLETED
LIQUI~ SMOKE TREATM~T
OF' FOOD CASINGS
REI,ATED APPLICATIONS
Canadian ~pplication No. 4l.2648-3 enti-tled "Tar-Dep1eted Liqui.d Smoke and Treated Food Casing,"
filed contemporaneously with ~his application in the name of Herman Shin-Gae Chiu, Canadian Application No. ~12653-0 entitled "Tar-Depleted Liquid Smoke Treatment of Food Casings," also filed contemporaneously with this application in the name of Myron ~onald ~icholson, and Canadian Application No. 401525-8 entitled "Liquid Coating Me~hod and Apparatus," filed April 23, 1982 in -the names of Chiu et al.
BACKGROUND OF THE_INV~NTION
Field of ~he Invention:
This inven-tion relates to: (a) a me-thod for preparing tar-depleted liquid smoke from a tar-containing aqueous liguid smoke solution, lb) a -tar-depleted smoke colored and flavored tubula~ food casing, (c) a tar-depleted aqueous liquid smoke solution with smoke color, odor and flavor capability, and (d) a method for preparing smoke colo.red and smolse flavored encased foodstuf.
Description of the Prior Art:
Tubular cellulosic food casings are used ex-tensively for processing a graat variety of meat products and other food items. The food casinys are generally thin-walled tubing of vaeious diametees 12~96-l s~

~2-prepared from reconstituted materials, such as regenerated cellulose. Cellulosic food casings may also be prepared with fibrous webs embedded in the wall thexeof, such casings commonly being referred S to as ~fibrous food casings.n, _ The many different recipes and modes of processing that are used by the processed food industry to suit different tastes, and even regional preferences, generally necessitate the use of food casings with a variety of characteristics. In some instances, for example, food casings are required to have multi~unctional uses wherein ~hey serve as containers during the processing of a food product encased therein, and then aiso Rerve as a protective wrapping Xor the finished product. In the processed meat industry, however, the food casings used in the preparation of many types of meat products, such as various types of sausages, such as rank~urters bolognas and the like, bee rolls, hams and the like, are fre~uently removed from about the processed meat product prior to slicing and/or final packaging.
Surface appearance and flavor are important factors in the commercial and consumer acceptance of processed meat products, and a common feature of most varieties of such products involves the use of "smoking~ for imparting charac~eristic flavor and color thereto~ The ~smoking~ of food products is generally accomplished by ~he food processor subjecting the food product to actual contact with smoke in a gaseous qr cloud like form. Such 'nsmo~ng" processes, however, have no~ been considered completely satisfactory for a variety of reasons, including the ineficiencies and lack of 32~

unlformity of the "smoking" operation. Because of the shortcomings experienced, many meat packers now employ various types of liquid aqueous solutions of wood-derived smoke cons~ituents, commonly called "liqilid smoke solutions" that have been developed and used commercially by the food processor in the processing of many types of meat and other food products. For convenience in this specification~
the as-purchased "liquid smoke solution" will be frequently reÇerred to as "as-is" liquid smoke.
The application of "liquid smoke solutions"
to meat products is generally carried out in a variety of ways, including spraying or dipping an encased food product during the processing thereof, ]-5 or by incorporating the "liquid smoke solution" in the recipe itsel. The actual operation of '~smoking" by spraying or dipping is not completely satisfactory due to inability to treat the encased product uniformly, and incorporation of "liquid smoke solutions" in the meat recipe does not always provide the desired surface appearance because oE
dilution of smoke ingredients. Incorporation in the recipe also reduces the stability of the meat emulsion, and will adversely affect taste if high concentrations are used. Application of liquid smoke to encased food products by the food processor, such as by spraying or dipping, also causes unwanted pollution and equipment corrosion problems for the food processor. In addltion, encased sausages treated by application of the liquid smoke during commercial processing have been found to yield, after peeling the casing from the treated encased food product, sausages which are lacking in smoke color uniformity from sausage to 3~
~4--sausage, and from batch of sausages to batch of sausages. What is even more undesirable is the lack ~f uniformity of coloration which often appears on the surface of the same sausage, including lisht and dark skreaks, light and dark blotches, and even -uncolored cpots which especially appear at the ends of sausages.
It has also been suggested, as ~or example disclosed in U.S. Patent No~ 3r330~669 to Hollenbeck, that application of a viscous liquid smoke solution to the inside surface of a deshirred tubular food casing by the food processor i~mediately prior to stuffing the casing with a sausage emulsion, results ln preparation of processed food products that exhibit acceptable color and smoky flavor after cooking and removal of the casingO However, the ~ollenbeck procedure has not been found practical and is n~t used commerciallyO The YiSCous liquid smoke solution disclosed by Hollenbeck is not practical for coating a casing on a high speed production line to produce a coated casing which can then be shirred by conventional methods and used as a shirred casing on an automatic stu~fing machine~ The high viscosity of the Hollenbeck coating solution limit the ca ing coating speed and, if a conventional method su~h as "slugging", also called ~bubble coatingn, is used to coa~ the inside of casing, the vlscous Hollenbeck coating ne~essi~ates frequen~ly cutting the casing 30 op~n to replenish the slug 9f coating material within the casing, which results in short lenyths o casing and thus makes continuous shirring impractical.

12896-l 7~
- s -Heretofore, however, it has been found that providing casings which afford special treatment or struc~ural characteristics to the food pro~uct can be more uniformly and economically accomplished by the casing manufacturer. This is especially true with the advent of, and wide commercial use of, automatic stuffing and processing equipment in the processed food industry.
Several methods of providing food casings with coatinss applied to a surface thereof are known and described in the patent literature. There is disclosed, for example, in U.S~ Patent No. 3,451,827 a spraying method for applying a variety of coating materials over the internal surface of small diameter casings. In U.S. Patent No. 3,378,379 to Shiner et al., a Wslugging~ method is used ~or applying coating materials to the internal surface of large diameter casings. While such techni~ues and others have been used in preparing commercial quantities of a varie~y of coated food casings, including casings where liquid smoke is employed as a component in ~he coating compositiont the casings produced thereby have been designed to meet particular commercial requirements and, to the best of my knowledge~ none of the prior art coated casings disclosed have been known to successfully impart a satisfactory level of "smoke" flavor and color to a meat produc~ processed therein. For example, in V.S. Patent 3,360,383 to Roce et al. and 30 in U.S. Patents 3,383,223 and 3,617,312 to Rose, there are disclosed coating compositions of various protein materials, such as gelatin, that employ liquid smoke solutions in amounts specifically reguired to insolubilize the protein materials.

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Such coated casings are disclosed as exhibitiny special adhesion properties required for the p:rocessing of dry sausages, which properties would therefore limit the suitability thereof for many other casing applications.
The prioe art patents teach application of liquid smoke to the internal surface of a casing, but a~-tempts to internally coat the casing during the manufacture thereof have been found to be costly and to limit the speed of a continuous high speed production line.
One solution to this problem as described and claimed in copending Canadian application No.
412653-0 filed by Herman Shin-Gse Chiu, involves treating the external surface of the food casing with an agueous ].iquid smoke compos;tion derived from natural wood. Chiu also discovered that when the food casing is cellulosic and formed of either non-fibrous gel stock or fibrous gel stock, the use of highly acidic ~pH of 2.0 -to 2.5) agueous liquid smoke results in the formation of a tarry deposit accumulating on the carrier rolls and the squeeze rolls of the smoke t.reatment unit, therebr eventually forcing shutdown of the treating system.
It was discovered that this problem could be overcome by at least partially neutralizing the as-is liguid smoke to precipitate the tar, and then treating the cellulosic gel stock casing with the tar-depleted liquid smoke. Chiu discovered that contrary to the previous s~ate-of-art belief, the tar-depleted liquid smoke. surprisingly, still possesses significant smoke coloring and flavoring capability.

One problem with the neutralization method of preparing the low tar aqueous liquid ~moke composît;on of the last-mentioned Chiu application is that the colorat;on capability or "Staining Power" of the wood-derived liquid smoke declines with increasing pEI or neutraliza~ion.
One object of this invention is to provide a method for preparing tar-depleted liguid smoke from a tar-containing wood-derived liquid smoke without requiring neutralization of the latter.
Another object of this invention is to provide a tar-depleted aqueous liquid smoke solution with high capability for imparting smoke color, odor and flavor to food products.
Still another object of this invention is to provide a tar-depleted, smoke colored and flavored tubular food casing with high capability for imparting smoke color, odor and flavor to Eood products encased therein, by treatment with the aforementioned solution in turn prepared by the aforementioned method.
A further object of this invention is to provide a method for preparing a smoke colored and smoke flavored foodstuff within the aforementioned tar-depleted, smoke colored and smoke flavored tubular food casing.
Other objects and advantages of the invention will become apparent erOm the ensuing disclosure and appended claims.

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S~AA~ 0- l~3 Inv~uslo~
In this invention a method i~ provided for the preparation of an aqueous smoke composition comprising contacting a tar-containing aqueous liquid smoke solution having an absorptive power (defined hereinaf~er) of at~least about 0.25 at 340 nm. wave length with either a nonreactive or reactive organic liquid solvent which has a hydrogen bonding solubility parameter of at least about 2.7 and which is immiscbile in the aqueous liquid smoke solution. To be useful in this invention, organic liquid solvents which react with the liquid smoke must form a derivative liquid solvent which is immiscible in the liquid smoke solution and exhibit the ~forementioned hydrogen bonding parameter in th~
liquid s~oke environmen~. The contacting is in a volume ratio between about 1:1 and about 65:1 of liquid smoke ~olu~ion to liquid solvent.
This contact is performed under extraction conditions to form a tar-enriched liquid solvent ~raction and a tar-depleted aqueous liquid smoke fraction, and the fractions are separated to provide the tar-depleted liquid smoke as the aqueous liquid smoke composition.
The invention also includes a tar~depleted smoke colored and smoke flavored tubular casing.
The lat~er is prepared by the steps of providing a tar-containing aqueous liquid wood smoke solution having an absorptive power of at least about 0.25 at 340 nm. and contacting same with a nonreactive immiscible organic liquid solvent having a hydrogen bonding s~lubility parameter in the liquid smoke environment of at least about 2.7. Alternatively, the organic liquid solvent may be reactive with the l2as~-l -9~ 7~

liquid smoke if it forms a deriv~tive liquid solvent ~hich is immiscible in the liquid smoke solution and possesses a hydrogen bonding parameter of at least

2.7 in this environment. The contacting is in a volume ratio between about 1:1 and about 65:1 of liquid smoke solution to liq`uid solvent under ~extraction conditions to provide a tar-enriched liquid solvent fraction and a tar-depleted aqueous liquid smoke fraction. The fractions are separated to provide the latter as the tar-depleted li~uid smoke. A surface of a tubular food casing is treated with the tar-depleted liquid smoke in a quantity ~uch that the casing develops an absorptive index (defined hereinafter~ of a~ least about 0.2 at 340 nm wave length for smoke coloring and smoke flavoring constituents in the casing wall.
~ his invention also includes a t~r-depleted aqueous liquid smoke solution with smoke color, odor and flavor capability, prepared by contacting a tar con~aining liquid smoke solution having an absorptive power of at least about 0.25 at 340 nm.
with a nonreactive organic liquid solvent which is immiscible in the aqueous liquid smoke solution and has a hydrogen bonding parameter of at least about 2.7 in the liquid smoke ènvironment. Alternatively, a reactive organic liquid solvent may be used if it satisfies the previously described criteria for the preparative method and the treated casing~ The contacting is in a volume ratio between about 1:1 and about 65:1 of liquid smoke solution to liquid solvent. This contact is also under extraction condltions to form a tar-enriched liquid ~olve~t fraction and a tar-depleted aqueous liquid smoke fraction. The fractions are separated to provide the ~ar-depleted aqueous liquid ~moke solution as the tar-depleted aqueous liquid smoke composition.

12896~1 7~

Still ~nother aspect of ~his inventio~
relates to a method for producing a foodstuff havin~
smoke col~r, odor and flavor including the steps of providing a tar containing aqueous liquid wood smoke solution comprising a mixture of smoke color, odor and flavor ccnstituents having an absorptive power of at least abou~ 0. 25 at 340 nm. The liquid smoke solution is con~acted with a nonreac~ive organic liquid solvent whicb is immiscible in the aqueous li~uid smoke ~olution and has a hydrogen bonding solubility parameter of at least about 2~7 in the liquid smoke environment. .Alternatively, the organic liquid solven~ may be reactive with the liquid smoke solution if it satisfies the previously discussed criteria. The contacting is in a volume ratio between about 1:1 and about 65:1 of liquid smoke solution to liquid solvent. This contact is under extraction conditions to form a tar-enriched liquid solvent fraction and a tar-depleted liquid smoke fraction, and the fractions are separated to provide a tar~depleted liquid smoke as an ~ueous liquid smoke composition. A surface of a tubular food casing is treated with the tar-depleted aqueous liquid smoke in a quantity such tha~ the casi~g develops an absorptive index of at least 0.2 at 340 nm ~ave length for the casi~ wall. The so treated casing is stuffed with foodstuf and the resulting enc~sed foodstuff ic processed und~r conditions ~ufficient to impart smoke color, odor and flavor to the encased foodstuff by transfer of smoke color, odor and flavor constituents from the casing to the encased foodstuff.
BRIEF DESCRIPTION OP DRAWINGS
Fig . 1 is a schematic view of apparatus suitable for t~eatment of food casing external '73~

surface wi~h ~ar-depleted liquid smoke in accordance with one embodiment of this invention.
Fig. 2 is a schematic view of apparatus similar to and performing the same functions as the Fig. l apparatus, but with a chamber for partially drying the tar-depleted liq~i-d smoke treated casing to a Aesired moisture content while in an inflated condition.
Fig. 3 is a schematic view of appa~atus similar to and performing the same function as the Fig. 2 apparatus but with means for partial drying of the tar-depleted liquid smoke treated casing while in a flat condition.
Fig. 4 is a graph.showing percent light transmittance as a function of as-purchased liquid smoke to liquid solvent volume ratio for several halogen-containing organic liquid solvents:
methylene chloride, bromochloromethane, chloroform and bromoform.
FigO 5 is a graph showing percent light transmittance as a function of as~purchased liquid smoke to liquid solvent volume ratio for various non-halogenated alcohols.
Fig~ 6 is a graph showing percent light transmittance as a function of hydrogen bondin~
solubility parameter for various organic liquid - solvents at a volume ratio of 1:1 of as~purchased liquid smoke to solvent.
Fig. 7 is a gr~ph showing percent light transmittance as a function of the sum total of hydrogen bonding solubility parameter plus percent solvent solubility in water, Por variou~ organic liquid solvents at a volume ratio of 6:1 of as-purchased liquid smoke to solvent.

12896-l A

FigO 8 is a graph showing percent light transmittance as a function of the sum total of hydrogen bondin~ solubility~parameter plus percent solvent solubility in water, for non-reactive and certain reactive organic liquid solvents at a volume ratio of 1:1 of as-purchase~ liquid smoke to sol~ent.
Fig. 9 is a graph showing ultraviolet transmittance and ultraviolet absorbance of casing extracts at various wave lengths for both as-is tar-containin~ liquid smoke treated casings and tar-depleted liquid smoke treated casings of this invention.
Fig. 10 is a graph showing percent light transmi~tance at 590 nm as a function of the as-is uid smoke to solvent volume ratio for several liquid smokes, and over a wide ranye of volume ratioO
Fig. 11 is a graph showing staining power as a function of volume ratio for relatively low liquid smoks to solvent volume ratios.
~ig. 12 is a graph showing ultraviolet absorptive index as a function of tar-depleted liquid s~oke loading in the food casing.
Fig. 13 is a graph showing percent nonvolatiles ~including taræ) in liquid smoke as a function of percent light transmittance.
D~SCRIPTION OF T~E PREFERRED EMBODIMEM~S
Food c~sings that are suitable for use in the present invention are tu~ular casings, and preferably tubular cellulosic casings~ that are prepared by any one of ~he methods well known in the ,art.. Such casings are generally ~lexible, thin-walled seamless tubing formed of regenerated cellulose, cellulose ethers such as hydroxyethyl cellulose, and the like, in a varie~y of diameters.

12~96-1 Also suitable are tubular cellulosic ca~ings having a fi~rous reinforcing web embedded in the wall thereof, which ar~ commonly called ~'ibrous food casings", as well as cellulosic casings withou~ the fibrous reinforcement~ herein referred to as -nnon-fibrous~ cellulosic casings.
Casings conventionally known as ~dry stock casings" may be used in the practice of this invention. Such casings generally have a w~er content within ~he range of from about 5 to about 14 weight per cent water if non-fibrous casing, or within the range of from about 3 to about 8 weight per cent water if fibrous casing, based on the total weight of casing including ~ater~
Casings conventionally known as agel stock casings" are casings which have higher moisture contents since they have not been previously dried, and such casings may also be used in the practice of this invention. Gel stock casings, whether fibrous or non-fibrous, are the type exhibiting the .
aforementioned tarring problem when treated by as~is liquid smokeO
Smoke color, odor and flavor con~tituents suitable for use in accordance with the pre~ent invention are generally those designated as being the color, odor and flavor constituents of as is liquid s~oke~
The term ~501u-tion~ as used herein is meant to encompa~s homogeneous ~rue solutions, emulsions, colloidal suspensions and the like.
Liquid smoke often is a solution of natural 'wood smoke constituents prepared by burning a wood, for example, hickory or maple, and capturing the natural smoke constituents in a liquid medium such 7'~

A

as water. Alternatively, the liquid smoke to be used may be derived from the destructive distillation of a w~od, that is, the breakdow~ o~
cracking of the wood Eibers into various compounds which are distilled out of the wood char residue.
Aqueous liquid smokes are generally very acidic, usually having a p~ of 2~5 or less and a titratable acidity of a~ least 3~ by weigh~.
Reference to the term "smoke color, odor and flavor constituents~, as used throughout this specifica~ion and in the appended claims with respect to the liquid smoke compositions and casings of this in~ention, is intended to reEer to, and should be understood as referring to, the s~oke color, odor and flavor constituents derived from liquid smoke solutions in their present commercially available orm.
The tar-depleted liquid smoke composition o this invention is derived from natural wood smoke constituents~ It is prepared by contacting a tar-containing source liquid smoke with suitable nonreactive or certain reactive organic solvents, as hereinaf~er described, to extract the tars therefrom. The source l~quid smoke is generally ~5 produced by the limited burning of hardwoods and the absorption of the smoke so generated, into an aqueous solution under controlled conditions. The limited burning keeps some of ~he undesirable hydrocarbon compounds or tars in an insoluble form, thereby allowing removal of these constituents from the final liquid.smoke. Thus, by this procedure, the wood constituents previously considered desirable by the manufacturers o liquid smoke are absorbed into the solution in a balanced proportion ,~
and the undesirable constituents may be removed.
The resultant liquid smoke solution still con~ains a significant concentration of tars because the manufacturers and users consider ~he dark colored tars to be necessary from the standpoint of imparting smoke color, odor~and flavor to foodstuffs. This smoke solution is representative of the whole spectrum of wood-derived smoke colors and flavors that are available. The apparatus and method f~r manufacturing typical liquid smokes of the preferred type is more fully described in U.5.
Patents Nos. 3,106,473 to ~ollenbeck and 3~873,741 to ~elcer et al.
As used herein, the term "at least partially neutralized~ is intended to refer to liquid smoke compositions having a p~ greater than : about 4, preferably having a pH wi~hin the range of from about 5 to about 9, and more preferably having a pH within the range of from abou~ 5 to about 6.
It has been found that the co~mercially available liquid smoke solu~ions are generally highly acidic, as discus~ed previously, and that they may, therefore, interfere with peelability of the casings if a peeling aid such as carboxymethyl cellulose is used. To aileviate this problem, a tar-deple~ed at least partially neutralixed liquid smoke may be employed in the practice of this invention..
The tar-depleted liquid smoke may be applied to the external surface of the ~ubular casing by passing the casing through a bath of the tar-depleted liquid smoke composition. The liquid smoke i8 allowed to con~act the casing prior to doctoring off any excess liquid smoke by passing the ~y ~ p ~ p ,~

~-16-casing through squee~.e rolls, or wipers, and the llke, for an amount of ~;me suff;cient for the casiny to ;ncorporate the desired amount of smoke color, odor and flavor constituents~ The process of passing the cas;ng through a trea~ment ba-th, also reEerred to ;n the art as a "dip bath" or a "d;p tank," may also be referrecl to in the art as a "dipping~' step. The tar~depleted liquid smoke composi-tion may al~ernat.ively be externally applied to the casing by methods other than dipping, such as spraying, brushing, roll--coating, and the like.
Alternatively, the tar-clepletecl liquid smoke compositlon may be applied to ~he internal surface of the casing by any of several well-known procedures described ;n U.S. Patent No. 4,171,381 to Chiu. These include slugging or bubble coating, spraying, and coating while shirring. The slugging method for coating the inside of a casing involves filling a portion of the casing with the coating material, so that the slug of coating material generally resides at the bottom of a "U'l shape formed by the casing being draped over two parallel rollers, ancl then moving the continuous indeEinite length of casing so that the slug of coating materia1 remains conEined within -the casing, while the casing moves past the slug and is coated on its inside wall by the coating material contained within the slug.
It may then be shirred by conventional methods, or prior to shirring, it may be dried and/or humidified to a water content suitable for shirring and/or Eurther processing. The need for conven~ional drying and/or humidification after the 12~96--1 preferably ex~ernal tar-depleted liquid smoke treatment depends on the water content of the casing after treatment and the type of casing. If the casing is a non-fibrous c~sing, a water content within ~he range of from about 8 weight per cent to about 18 weight per cent wa~e~ immediately before shirring is typical, and for fibrous casing a water content ~ithin the range of from about ll weight per cent to about 35 weight per cent water i~mediately before shirring is typical, where per cent is based on the total weight of casing încluding water.
Various organic solvents ~ere tested as tG
their potential for extracting tars from lS as-purcha~ed liquid smokeO The procedure was as follows. Various ra~ios of liquid s~oke to solvent were prepared and ~horoughly mixed. The sample was allowed to se~le overnight in order to separate the lower solvent layer containing the extracted tars from the aqueous upper liquid smoke layer. After gravity separation, a l ml. aliquot of the reduced tar aqueous liquid smoke layer was mixed with lO ml of water and its turbidity (tran~mittance at 590 nm, the wave length oE light) was measured on a spectrophotometer. The higher the percent transmittance reading, the lower the residual tar concentration in the aqueous liquid ~moke. As used herein, ~light transmittance of aqueous liquid smoke refers to the latter's intrinsic light transmittance without addition of materials which may significantly affect the.percent light transmittance.
Four halogen- ubstituted methane liquid 30lv~nts were tested in the first series of solvent tests, and Figure 4 is a series o graphs showing 1~89~-l ,~
percent light transmittance as a function of the as-puxchased liquid smoke to liquid solvent volume ratio for meth~lene chloride (solid line), bromochloromethane (long dash line), chloroform (dash-dot-dot-dash line), and bromofor~ (short dash line). In each instance the-~liquid smoke was "Royal Smoke AA" purchased from Griffith 1aboratories.
It will be apparent from Figure 4-that in general the highest levels of light transmittance ~re achieved with the greatest quantity of solvent relative to liquid smoke. In 2 preferred embodiment of this invention ~he reduced tar-content aqueous liquid smoke composition has at least 50~ light transmittance, and the method for preparing the reduced-tar content composition requires use of a liquid smoke solution to liquid solvent volume ratio so as to provide a tar depleted liquid smoke having at least 50% light transmittance. As illustrated in Table T and Figure 13 (both discussed hereinafter), lower levels of light transmittance indicate that the preferred degree of tar removal from the as-purchased liquid smoke was not achieved. Using this light transmi~tance criteria, it appears that the suitable range of liquid smoke/liguid solvent 25 volume ratio depends on the particular liquid solvent and the total acid content-absorptive power of the liquid smokeO It will be recognized that suitable solvents must be substantially immiscible . with ~he liquid smoke for suitable extraction : 30 mechanics. Distinct layering of the two phase facilitates actual gravimetric separation. It will be r~cognized fur'cher that complete separation of the aqueous liquid ~moke and the organic solvent is not possible and, depending on miscibility, a small 12~9~-l amount of the organic solvent will remain in ~he aqueous liquid smoke. By way of illustration, about 1~ by weight me~hylene chloride remains in the aqueous liquid smoke after ~he tar-containing fraction has been removed. Other data shows that methylene chloride is non-d~tectable in casings -treated with reduced-tar compositions in accordance with this invention.
Figure 4 demonstrates that with methylene chloride (CH2C12) a5 the or~anic solvent~ the liquid smoke solution to methylene choride volume ratio may be as high as about 7:l without significant loss of transmittance, and as high as about L7:1 while still maintaining the preferred 15 level of at least 50% transmittance. Figure ~ also illustrates that with bromochloromethane (C~2BrC1) as the organic solvent, the liquid smoke solution to bromochloromethane volume ratio may be as high as about 15:1 without significant loss of transmittance, and up to abou~ 25:1 while still maintaining the preferred level of a~ least 50%
transmittance. From Figure 4 i~ is furtller appa~ent that with chloroform (CHC13) as the organic : solvent, the transmittance continuously declines 25 from the maximum value as the liquid smoke/chloroform ratio increases. This volume ratio should be between about 1:1 and about lÇ:l to achieve the preferred transmi~tance of at least 50~. Figure 4 shows that with bromoform (CHBr3), 30 only a very low volu~e ratio ~between about 1:1 and about 3:1) is necessary ko achieve the preferred at least 50% transmittance. ~igher values could be achieved with multip]e liquid extraction steps for this and any other suitable liquid solvent. That is, the aqueous liquid smoke fraction from a first liq~id solvent extraction stage is mixed with 2dditional liquid solven~ and again separated into a further tar-depleted aqueous liquid smoke fraction and a tar~enriched liquid solvent fraction layer.
It will be recognized that the practitioner may employ as many liquid extraction stages as needed to achieve the desired level of transmittance.
Further~ i~ will be understood that different suitable organic solvents may be used in multiple solvent extraction steps according to this invention, and that mixtures of solvents are suitable if the mi~ture possesses the preYiously defined requirement of hydrogen bonding parameter (at least 2.7) and immiscibility in the liquid smoke environment.
In a second series of solven~ ~ests, other halogen substituted hydrocarbon solvents were tested for tar-depletion capability by measuring the resulting smoke compositions' transmittance usiny the aforesaid procedure. Various concentration admixtures of the solvents with the same as-is liquid smoke were tested and the results were correlated with hydrogen bonding parameters. These tests are summarized in Table A.

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C ~ C~ o o o O ~ ~

T '' ' ~ ~ , o O O o a ~ u7 r~ , c C b a . , ~. O O O , O ~ 8 U
~0 ~ UC
b j i ~ , " . o _, ~ " O

t ~ ~ O D .c o ~ ~
a' ~c t ~ 0 ~ ^ ~
~ ~ C 2~ t~ ~ ~C tl ~ t~ ~ ~
~1 ,1~ 1 N rl ~ 8 .. ~ .. 21 ~ o u al e ~, C t~ ~0 t, O t~ Vo t~ U ~ O *
~7 t" t~ _t~ O t~ ;U ~U U

U~ O ~

-22~

Inspection of Table A reveals ~hat of the tested halogen-substitu~ed hydrocarbon liquids, only t~ose possessing hydrogen bonding parameters above about 2.7 are suikable for use in this invention.
The tested liquids below this value produce .extracted liquid smokes having light transmittance values which are either unacceptably low or zero.
In another series of experiments~ a group of non-halogenated alcohol liquids were tested ~s to ~heir potential for extracting tars by the aforedescribed spectrophotometric p~ocedure and at various liquid smoke/solvent ratios using as-purchased Royal Smoke AA. These volume ratios ranged from 1:1 to over 12.1, depending on the particular alcohol liquid/ and the results are summarized in the graphs of Figure 5. In these yraphs percent light transmittance is ~hown as a function of the as-purchased liquid smoke to solvent volume ra~io for six alcohols identified by the following let~er~: al 2-ethylhexanol~ b) hexyl CELLOSOLVE, or the monohexyl ether of ethylene glycol, sold by Union Carbide Corporation, 270 Park Avenue, New York City, c~ n-octyl alcohol, d) n-hexyl alcohol, e) n-bu~yl alcohol, and f) phenyl CELLOSOLVE, the phenyl ether of ethylene glycol also sold by Union Carbide Corporation. Figure 5 demonstra~ed ~hat each of ~hese alcohol solvents is use~ul in the practice of this invention over a particular range of liquid smoke to solvent ratios, and the ranges vary ~epending on the solvent. By way of illustra~io.n, ~he prac~itioner may use Figure 5 to select a ~oyal Smoke AA to n-octyl alcohol volume ratio between about 1:1 and 13:1 ~o practice this invention because the re~ulting tar-depleted liquid smoke has light transmittance of at least about 50%. Higher liquid smoke to liquid solven-t ratios result in unacceptably low light transmittance percentages.
It has been indicated that organic liquid solvents useful in this invention must have a hydrogen bonding solubility parameter of at least about 2.7. As used herein, this parameter or character of the solvent may be calculated from 10 known literature or experimental vapor pressure data such as the heat of vaporization at 25C. The total solubility pa.rameter (UT~ may be determined using the relationship of Equation (1).
~ ( ~ H - RT) d.1 1/2 (1 ) 5 where: H25 = ~leat of vapori~ation at 25C
R = Gas constant T = Temperature d = Density at 25C
M ~ Molecular weight The total solubility parameter value is separated into its hydrogen bonding (S~I) or polar (~p) and nonpolar (~np) constituents. The following relationships are useful for determining the hydrogen bonding parameter value (~
2S log ~ = 3.39066 Tb _ 0.15848 - log d- ( ) where: ~ = Aggregation numher Tb = Boiling point in degrees absolute Tc = Critical temperature in degrees absolute M = Molecular weight d = Density ~ H ~T

3~
-2~-The theoretical basis for use of solubility characteristics is discu~sed in the literature.
Tabulation of param?ters have been published in works by C. M. ~ansen, ~The Three Dimensional S Solubility Parameter and Solvent Diffus.ion Coeffi~ient,~ Danish Technica~l Press, 1967, Copenhagen~ The hydrogen bonding solubility parameters listed herein were obtained exclusively from the compilation by ~. L. Hoy, "Tables of Solubility Parameters~ Union Carbide Corporation, 1975. This may be obtained from Union Carbide Corporation, Chemicals and Plastics Division, River Road, Bound Brook, New Jersey 08805.
The aforedescribe~ spectrophotometric procedure wa~ employed to measure the percent light transmittance for a varie~y of organic liquids having different hydrogen bonding solubility parameters using as purchased Royal Smoke AA, at a smoke to solvent volume ratio o~ 1:1. The results of these ~es~s are summarized on Table B and the graph of Figure 6.

12~96-1 .

3~

,~
Table B
~-Bo~ding Parameter and ~ Light Transmittance _ _ at a 1 1 S~oke to Solvent Ratio ~-Bonding Solvent Parameter~ Light Transmittance -- _ Acids 2-Ethylhexanoic acid 5.68 11.3 Alcohols 2-EthylhexanG1 5.85 79.2 Hexyl CELLOSOLVE 5.90 9B.2 n-Octyl alcohol 6.08 B7.2 n ~exyl alcohol 6.68 94.6 n-Butyl alcohol 7.55 81.0 Phenyl CELLOSOLVE 7.84 99.4 Aldeh~d-es Propionaldehyde 5.38 86.8 Alkanes Decane 0 Octane . 0 Hexane 0 0 2,2-Dimethylbutane 0 0 Cyclohexane 0 ~ 0 Amine~
Tri-n-butylamine 1.93 0.2 Aromatics n-~utylbenze~e 0 ~umene ` 0 0.6 Toluene ' 0.B0 0.3 - p-Xylene 0.97 Esters 2.Ethylhexyl acetate 2.62 16.3 Butyl acetate 3.30 a7,s Ethyl acetate 4~35 92.5 Ethers Isopropyl ether 0O75 0.2 n-Butyl ether 2.20 0 Ethyl ether 2.~3 74.2 ~26 Table B (~
___ H-Bonding Pa~ameter and % Light Transmittance at a 1~1 Smoke to Solvent Ratio ~-Bonding Svlvent Parameter~ Light Transmittance ~alo~enated Perchioroethylene - ,0 _ Butyl chloride 1.71 0 Chloroform 3.09 85.2 1.0 Methylene chloride 4.70 86~4 Ketones Isophorone 1.5Sa97.0 Diisobutyl ketone 1.88 36.7 Methyl isobutyl ketone 2.88 92.2 Acetophenone 4.03 98~0 MEK/toluene~ 2.71 74.8 MEK/2-ethylhexanol~ 5.23 91.4 avalue is 2.7 if equilibrium concentration of enol is 35 mol%.
bmethyl ethyl ketone pre~ent in 50 weight ~ concentration.

1289S-l Inspe~tion ~f Figure 6 reveals that there is a sharp increase ~almost vertical slope) in the percent light transmittance for the ~ested organic solvents as the H-bonding solubili~y parameter is S increased in the region of about 2.7. While this phenomenon is no~ ully understood, it appears to be due to the threshold type interaction of the solvent with the tar components resulting in preferential solubility of such components. This solubility is related t~ the solvent's physico-chemical character and can be predicted by the measured hydrogen bonding parameter walue if significantly above 2.7.
For organic liquids having H-bonding solubility parameter values of about 2.7, the solvent effectiveness for extraction of liquîd smoke tars is very sensitive, and should be determined by experiment. For example, Table C ~discussed hereinafter) shows hat ethyl ether (~ 2.73) performs adequately while ~able A shows that l,l-dichloroethane (SH 2-74) is by itself unsatisfactory or use in a singïe extraction step according to this invention. Accordingly, it appears that in this threshold transition between acceptable and nonacceptable solvents, some anomalies may occur with respec~ to function and H-bonding solubility parameter value.
Referring to Table B, one exception to the hydrosen bonding solubility parameter - percent light transmittance relationship is isophorone, which has a low ~-bonding pasameter of 1.55~ but which produces an extracted liquid smoke having a high light transmittance of 97.0%. A probable explanation is that in ~he acidic medium of Royal Smoke AA, one would expect a significant 7~ '~
-2~-,~
concentration of the enol by way of equilibrium. As calculated by the aforedescribed procedure, the H bonding solubility parameter for the enol is 4.8, so that if the enol is present at 35 mol ~ (65 mol~
isophorone), the ~-bonding parameter for the two tautomers is 2.7. Such an enol concentration is reasonable for this system.
Referring again to Table B, another exception ~o the hydrogen bonding solubility parameter - percent light transmittance relationship is 2-ethylhexanoic acid, which has a high hydrogen bonding parameter of 5.68 but a low light transmittance of only 11.3 ~. One possible explanation as to its failure to function adequa~ely, considering i~s high hydrogen bonding parameter, could be dimerization in the acidic environment of the liquid smoke. The hydro~en bonding parameter of such a dimer may be much lower than the value reported for ~he monomer.
~ It has also been determined that the required ~-bonding parameter of at least about 2.7 (and preferably at least 50~ light transmittance indicating effective tar removal~ may be achieved by mixing of at least two organic liquids, one being miscible with the liquîd smoke and having a ~-bonding parame~er of grea~er than about 2.7~ and another having an unsatisfactory low ~or even negligible) H-bonding parameter and insoluble in ~he liquid smoke. By way of illustration, in the Table B - Figure 6 ~ests, methyl ethyl ketone (MEK) was found to be miscible with the tar-containing liquid smok~ at a liqui~ smoke/solvent volume ra~io of l lo ~lso, toluene did not extract the tars from the liquid smoke and has a H~bonding parameter of 'jJ3,~

, 0.80. However, a 50/50 (by weight) mixture of MEK
and toluene has a calculated H-bonding parameter o 2.71 and demonstrated a 74.8~ light transmittance of the liquid smoke upon extraction with the mixture.
.In still another series sf experiments, the ~Table B group of organic li~ulds were tested for percent light transmittance at higher smoke to solvent volume ratios by the same spectrophotometric procedure using as-purchased Royal Smoke AA. These liquid smoke to solvent volume ratios were 3:L, 6:1, 12:1 and 24:1; the results are summarized in Table C
and the Figure 7 graph.
Inspection of Table C reveals that at a liquid smoke to solvent ratio (also referred to herein as the ex~raction ratio~ of 3:1, for most sol~ents the percent light transmittance was similar to or slightly le s than for an extraction ratio of 1:1. In general, the suitability of the solvent for use in the present invention is the same for the two extraction ratios, i.e., the solvent provides the preferred light transmittance (for extracted liquid smoke) above 50~ for both ~atios or below 50% for both ratios as defined by the H-bonding parameter of about 2.7. There are three exceptions to this generalization: propi~naldehyde, ethyl ether, and the mixture of MEK/2-ethylhexanol~
Table C al50 indicates ~hat at liquid smoke to solvent ratio of 6:1 and higher, some of the solvents which were suitable at lower extraction ratios are no longer suitable, whereas others remain suitable. By wa~ of illustra~ion, chloroform and methylene chlori~e are suitable at high extxaction ratios whereas ethyl acetate provides light transmittance of only 4.5% at an extraction ratio of 12~96-1 ~3~7~3~L
-30~

6:1. One reason for this observed phenomena i~ the solvent's solubility in water and, hence~ its anticipated solubility in the liquid smoke, and the relationship is defined for purposes of this 5 invention by reference to the sum total of the ~-bonding solubility parameter plus the weight percent solvent sol~bility in ~ater ~hen the extraction ratio is greater than about 6~ ore specifically, the sum total should not exceed about 9 or the water solubility of the solvent is too high for practicing the invention, as demonstrated by percent light ~ransmittance below about 50~.
Referring again to chloroform and methylene chloride, because of their low water solubility, their sum totals are 3.9 and 6~0, respectively, and both have high light ~ransmittance values of 8004 and 82~0% at an extraction ratio of 24:1.
Therefore, they are suitable for practicing this invention at high ratios. In contrast~ ethyl acetate has a sum total of 12.4 because of ~igh water solubility, and a low light transmittance of only 4.5~ at an extraction ra~io of 6:1. Therefore, ethyl acetate is not suitable for prac~icing this invention at high extraction ratios.
Figure 7 shows that the percent light transmittance is relatively constant at a very high level of at least 85~ for ~um totals between about 2.7 and about 7, and ~hen declines at progressively increasing rates through at least R. The percent light transmittance drops below about 50~ for sum totals exceeding about 9, and solvents having the latter characteristic are not suitable or practicing the invention.
Reviewing the Figure 5 graphs of certain alcohol solvents in the context of the ~-bonding parameter plus water solubility sum total as set 3~ 3~

forth in Table C, it will be noted that five of the 5iX alcohols satisfy this relationship, but 2 ethylhexanol does not. Even though its sum total is only 5~9, i~ demonstrates an unacceptably low light transm.ittance of 44.8% at an extraction ratio of 6:10 The reason for thi~ ~xception to the previously defined sum total-e~traction ratio relationship is not understood, but may be due to steric considerations.

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, Figure 8 is a graph showing ~he percent light transmittance for the organic liquids of Tables B and C, as a function of the sum to~al of the ~-bonding solubility parameter plus the weight percent solvent solubility in water for an extraction ratio of 1:1 (llquid smoke to solvent ~ ~olume ratio). As with the ~-bonding parame~er alone (Figure 6), the light transmittance rises almo~t vertically at a sum ~otal of about 2~7, and remains at a very high level of about 90% for sum totals at least as high as 15. Unlike the Figure 7 graph for 6~1 extraction ratio, the light transmittance for ~he 1:1 extrac~ion ratio does not decline at sum totals above about 7.
Ano~her group of ~olvents were tested for light transmittance by the same spectrophotometr.ic procedure for light transmittanc2/ using extraction ratios of 1:1, 3:1 and/or 6:1 and as-purchased Royal Smoke AA. The data from the~e ~ests is summarized ~0 in Table D. Inspection of Table D reveals that most of the organic liquids performed the extrac~ion in acçordance with the previously discussed relationship of extraction ratio and sum total of H-bonding ~olubility parameter and weight percent solubility in water~

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36~

Another requirement of organic liquids suitable for use in thi~ inven~ion ~s single constituent solvents is tha~ they be nonreactive and immiscible with ~he tar-containing liquid smoke or, if reactive, ~he resulting derivative solvent must also be immiscible in the tar-containing liquid while possessi~g the necessary criterion of at least about 2.7 H-bonding parameter value in the liquid smoke environment. Two types of reactive solvents have been included in the preceding Tables C and D
data. They are the organic acids and amines.
A group of organic liquids generally unsuitable for use in this invention as single constituent solvents are the alkyl amines. In the low p~ environment of tar~containing liquid s~oke, an acid-base exothermic reaction occurs and the resulting quaternary salt usually becomes more soluble than its precursor. Phase distinction is lost, hence extraction is not possible as demonstrated by tri-n-butylamine (Table C~.
However, with certain amines such as di-(2-ethylhexyl~amine, experimental observations show that the immiscibility remains high between the resulting derivative qua~ernary salt solvent ~nd the tar-containing liquid smoke solution~ Also, since the hydrogen bonding capability of the quaternary salt i5 known to be higher than its precursor, the derivative solvent is believe~ to have a hydrogen bonding solubility parameter which is higher than 2.35 (the Table D value for the precursor) and most likely above about 2.7. For these reasons, the quatérnary salt derivative solvent of di-t2-ethylhexyl)amine ln the liquid smoke environment is a suitable single constituent solvent~

12~96-l -37~

When considering use of the reactive type of solvent, the practitioner should insure that the desired chemical balance of the liquid smoke is not upset by the solvent reaction. It is possible that certain reactive solvents m~y,form deriva~ives which are functionally sui~able, but adversely alter the liquid smoke's coloring and 1avoring charac~eristics. For this reason, .it is preferred to use the nonreactive type of organic liquid solvent in the practice of this invention.
One method of treating ~he casing with ~he t~r-depleted liquid smoke of this invention is shown in Fig. 1. ~n Fig. 1, a flattened, tubular, cellulosic sausage casing 10, is e~ternally treated with a tar-depleted liquid smoke composition during its passage over lower and upper guide rolls 13 through dip tank ll which contains the tar-depleted liquid s~oke composition 12n The casing passes over lower and upper guide rolls 14 after exiting the dip tank, and ~hen passes between squeeze roll~ 20 which minimize any excess carry-over of ~he liquid smoke composition. The total contact time of the casing 10 with the tar-depleted liquid smoke composition 12 in the dip tank 11, and with e~cess liquid ~moke composition on the casing passing over the guide rolls 14 before the casing passes through the squeeze rolls 20, will determine the amount of smoke color~ odor and flavor constituents o~ the tar-depleted liquid smoke composition that the casing will incorporate~ The total contact time is measured from polnt A to point B in Fig/ 1. After the casing passes ~hrough squeeze rolls 20? it passes over guide roll 23 and is wound up on reel 24. The casi~g is then sent on to conventional l2as6-l 38~

further processing, including conventional humidific~t.ion, as may be required, and conventional shirringO
The embodiment illustrated in Fig. 2 differs from that illustrated in Fig. 1, in ~hat in - Fig. ~ the casin~ after passing through squeeze rolls 20 is passed into a heating and drying chamber 21~ wherein it is dried to the proper moisture content. The casing is inflated by a bubble of air maintained in a relatively fixed position between queeze rolls 20 and 22 by the sealing action of rolls 20 and ~2. The heating chamber 21 can be any type of heating device, such as circulating hot air chambersl which will dry the sausage casing to the proper moisture content. After the casing passes out of the heating chamber 21 and through squeeze rolls ~2, it passes oYer guide roll 23 and IS wound up on reel 24. The casing is then sent on to conventional further processing~ including conventional humidification, as may be required, and conventional shirring.
The embodiment illustrated in Fig. 3 differs from that illustrated in Fig~ 2, in that in Fig. 3 the casing is dried in a flat condition while passing over guide rolls 25.
It is to be noted that the tar-depleted liquid smoke which i~ coated on the casiny surface, whether externally coated or internally coated, does not exist solely as a sur~ace coating. Smoke color, odor and flavor constituents which are coated on the surface penetrate the cellulosic structure of th~
casi~g as the cellulose absorbs the mois~ure of the smoke solution. Inspection of the cross-section of the casing wall discloses a color gradation across 12896~1 the casing wall, with the smoke treated surface having a darker color than the surface on the opposite side of the casing wall. Accordingly, as used herein, the term ~coating~ is to be understood to mean that the casing wall is not only coated with smoke constituents but that-t~e casing wall is also .impregnated with smoke constituents.
The tar-depleted liguid smoke compositions of the present invention may also con~ain other ingredients which may be suitably used in treating a tubular food casing, to which the smoke constituents are applied, e~g., glycerine and/or propylene glycol which may be used as humectants nr softening agents, and the like.
Other ingredients which are normally used in the manufacture o~, or for further treatmen~ of the food casings, e.g. ? cellulose ethers and mineral oil, may also be present in the casing if desired, and they may be used in the same manner and amounts as if the tar-d2pleted liguid s~oke treatment had not been used.
In particular, agents for improving the peelability of the casing~ from food products such as sausages, e.g., frankfur~ers, bolognas and the like, may be optionally coated on the internal surface of the casings before or after the external application of tar-deplet@d li~uid smoke to the casing, and before or during shirring. If the tar-depleted liquid smoke is applied to the casing internal surface, the peelability agent i5 preferably applied firstO Such peelability enhahcing agents include, but are not limited to, carboxymethyl cellulose and other water ~oluble cellulose ethers, the use of which is disclosed in 12896-1 .

3~

U.S. Patent 3,898,348 issued Augus-t 5, 1975 to Chiu et. al., "Aquapel", a Hercules, Inc. trademarked product comprising alkyl ke~ene dimers, the use of wh:Lch is further disclosed in U.S. Patent No.
3,905,39~ issued September l6, 1975 to H.S. Chiu, and "Quilon", an E.I. Dupont de Nemours Co., Inc.
trademarked product comprising Eatty acid chromyl chlorides, the use of which is further disclosed in U.S. Patent No. 2,901,358 issued August 25, 1959 to W. F. Underwood et al.
The peelability enhancing agent may be applied to the internal surface of the tubular food casings by using any one of a number of well known methods. Thus, for example, the peelability enhancing agent can be introduced into the tubular casing in the forrn of a "slug" of liquid, in a manner similar to that disclosed, for example, in U.S. Patent No; 3,378,379 to Shiner et al.
Advancing the casing past the liquid slug coats the inner surface thereof. Alternatively, the peelability enhancing agent may be applied to the internal surface of the casing through a hollow mandrel over which the casing is advancing as, for example, a shirring machine mandrel in a manner similar to that described in U.S. Patent No.
3,451,827 to Bridgeford.
Casings prepared using the method of this invention are also suitable for the processing of what is conventionally known in the art as "dry sausages." Unlike other types of non-~ibrous and f~ 3t~

Eibrous casings which are preferably easy to peel ~Erom the Eood product, either by the food processor before sale to the customer or by the consumer, "dry sausage" casing preferably adhere~ to the food prodnct during and after processinq. "Kymene," a llercules, Inc. trademarked product which is a polyamide epichlorohydrin resin, the use of which is Eurther disclosed in U.S. Pa-tent ~,378,379, issued April 16, 1968 to Shiner et al., may optionally be ;nternally coated on the internal surface of a casing treated with tar-depleted liguid smoke by the method of -this invention, to improve the adhesion of the casing to food products processed therein.
The invention will now be more clearly understood by reference to the following examples which are set forth as being merely illustrative of the invention and which are not intended, in any manner, to be limita-tive thereof. Unless otherwise indicated, all parts and percentages are by weight and all casing related percentages are based on the total weight of -the casing.
EXAMPLE I
This example illustrates the preparation of a liquid smoke composition oE this invention. To 0.47 gallons (1.8 liters) of methylene chloride was added 4.7 gallons of as-purchased (as-is) liquid fimoke solution "A" ("Royal Smoke AA"
from Griffith Laboratories, Inc. haviny an absorptive power of about 0.6 at ~40 nm), and the liquids were then thoroughly mixed by repeated inverting of the container. The methylene chloricle containing the -tars was separated from the liquid l2as6-l 3j~
~2-sm~ke by gravity, i.e~ the tar-enriched methylene chloride lower layer was drained off until ~he tar-depleted liqui~ smoke upper layer appeared as detected by vi~ual observation. ~he resul~ing aqueous liquid smoke composition was substantially tar-free as dete~min~d by a-q~alitative wate~
compatibility test in which a sample of the liquid smoke was mi~ed with water and observed for tar precipitation or lack thereof. The p~ of a portion Of the a~ueous liquid smoke composition wa~ then adjusted to 5.0 by adding a sufficient amount of a 50~ NaO~ solution to the smoke solution. The pH of a sample of as-is li~uid smoke was similarly adjus~ed ~o 5~0. The chemical compositions of tbe four liquid smoke solutions involved in this Example I are ~hown in Table E. The total acid content was measured by the steam distillation-titration procedure desribed hereinafter. Phenol and carbonyl determinations for liquid ~moke solutions are made by the following procedures.
Determination of Phenol and Carbonyl Content of Liq~ d Smoke For sample preparation~ all samples are filtered through Wha~man No. 2 f ilter paper or equivalent, and refri~erated upon receipt or after preparation until the time of analysis to avoid possible polymerization. ~istilled ~ater is u~ed for all dilution~. The samples are diluted with water in two steps, beginning with a 10 ml.
~uantity~ In the first s~ep the dilution is to a total volume of 200 ml., an~ in the second step 10 ml. of the first-solu~ion is further diluted to a total volume of 100 ml. For phenol dete~mination, 5 ml. of the secsnd solution is further diluted in a 3'~

third step with distilled water to a total volume of 100 ml. For carbonyl determination, 1 m'.. of the secGnd solution is further diluted with carbonyl-free methanol to a total volume vf 10 ml.
~or the phenol de~ermina~ion, the reagents are: ~
1. Boric acid-potassium chloride buffer pW 8.3. Dilute the indicated quantities of the solution to 1 liter with water.
0.4 M boric acid - 125 ml.
C.4 M potassium chloride - 125 ml.
0~2 M sodium hydroxide - 40 ml.
2. 0.6~ NaO~
3. Color reagent - -N-2,6 trichloro-p-benzoquinoneimine Stock solution: dissolve 0.25 gm. in 30 ml. methanol and keep in refrigerator.

4. 2,6-dime~hoxyphenol standards Prepare solutions of 1 to 7 micrograms/ml. of DMP in water for standard curv~.
This procedure for phenol determination is a modified Gibbs method based on the procedure described in Tuckerr I.~. ~Estimation of Phenols in Meat and ~atn, JACAC, XXV, 779 (1942). The reagents are mixed together in the following order:
1st - 5 ml. of p~ 3 buffer.
2nd - 5 ml. of dilution of unknown diluted liquid smoke! or of standard 2;6-dimethoxyphenol ~olution, or

5 ml. of water for blank~
3rd - Adjus~ pH to 9.8 using 1 ml. of 0.6 NaO~.

4th - Dilute 1 ml. of color reagent stock olu~ion to 15 ml. in wa~er. Add 1 ml. of diluted color reagent.
Prepare just before adding.
5th - Allow color to develop for exactly 25 minutes at room temperature~
6th - Determine absorbance at a wave length 3f 580 nm in a 1 cm colorimeter tube wi~h a Spectronic 20 or equivalent.
7th Prepare a st~ndard curve using absorbance as the abscissa and standard concentrations a~ the ordinate. Extrapolate concentration of DMP in li~uid smoke dilutions from this curve.
8th - Calculate mg DMP/ml liquid smoke using the following equation:
pp~ DMP (~r~o~l~ur~e) ~dllutlon f ctor YD 001 cq~4ng D?~/~l To calculate mg DMP/g liquid smoke, divide result of above equation by the weight ~g~ of 1 ml of liquid smoke.
Por carbonyl determination, the reaqents are:
1~ Carbonyl free methanol, To 500 ml. of methanol add 5 gm. of 2,4 dini~roph~nylhydrazine and a few drops of concentrated ~Cl. Refl~x three hours, then distill~
2. 2,4~dinitrophenylhydrazine solution~
Prepare saturated ~olution in carbonyl-free methanol using twice recrystalliæed product. Store in refrigeratsr and prepare fresh ev~ry two weeks.

J~

3. KOH solution~ 10 gm. i.n 20 ml~ of di~tilled H2O, diluted to 100 ml.
with carbonyl-free methanolO
4. 2-butanone standard. Prepare sol~tions of 3.0 to 10 mg~ of 2~butanone in-lD0 ml. carbonyl-free ~ methanol for a standard curve.
The procedure is a modified Lappan-Clark method based on the procedure described in their article ~Colorime~ric ~ethod for Determination of Traces of Carbonyl Compounds n ~ Anal. Chem. 23, 541-542 (1959). The procedure is as follows:
1st - To 25 ml~ volumetric flasks containing 1 ml. of 2,4~dinitrophenylhydrazine reagent (prewarmed to insure saturation) add 1 ml. of diluted liquid smoke ~olution, or 1 ml. of standard butanone solution, or 1 ml. of methanol (for reagent blank~.
2nd - Add 0.05 ml. o concentrated EICl to all 25 ml-. flasks, mi~ contents of - each, and place in water bath for 30 minutes at 50C.
3rd - Cool to room temperature and add 5 ml. ROH solution to each.
4th - Dilute conte~s of each flask to 25 .
ml. with carbonyl-free methanol.
5th ~ Read at 480 nm against methanol blank ~et at absorbance of 0, (cuvettes -0.5 x ~ inches (10.2 cm) or -~6~

equivalent)O Use Spectronic 20, or equivalent.
6th - Plot absorbance versus 2-butanone (MEK) concentration in mg. per 100 ml. for standard cu~ve.
7th ~ Prepare a stclndard curve using absorbance as the abscissa and standard concentrations (mg ~EX/100 ml) as the ordinate. Extr~polate concentration of ~EK in li~uid smoke dilutions from this curve.
8th - Calculate mg ~EK/100 ml liquid smoke hy the following equ~tion:

al~sEK (~ro~ d curv~ O dilution ~ICtO~ ~9 ~1eK/1001Dl liq a~oke To calculate mg MER/g liquid smoke, divide the resul~ of the above e~uation by the weight (in grams) of 100 ml of smoke.

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Table E shows that the aqueous liquid smoke composition prepared in accordance with this invention has a substantially different chemical character Prom the as-is ~ar Gontaining aqueous liquid smoke. On a weight basis, the tar-depleted compositions of l'able E, samples E2 and E~, have less than about one-half of the phenol content of the tar-containing aqueous liquid smoke composition from which they are derived (Sample No. El), and this represents a preferred compositlon of the inven~ion. While the da~a in Table E show~ tha~ the extraction does substantially al~er the ~otal acid content and the carbonyl concentration, other test work indicates that no conclusion can be drawn Prom my work xe~arding the effect of extraction upon total acid content or carbonyl concen~ration. While the practice sf this inventiQn greatly reduces the phenolic component concentration in a liquid smoke composition, it does not adversely affect the ~0 composition's protein staininy ~color development) ability, or its natural odor or flavor at~ribu~es, as demonstrated by ensuing Examples.
It is also apparen~ from visual inspection of samples of the Table E compositions that those embodying this invention contain substantially less high molecular weight tars, since they are noticeably lighter in color~ ~dditionally, they are totally miscible with water.
EXAMPLE LI
This example illustrates the treatment of a non-fibrous cell~lo~e Pood ~asing by the method of this invention with liquid smoke components o Example I as well as with nCharsol C-10", purchased from Red Arrow Products CoO and having an absorptive '7~

~9 power oL about 0~4 a~ 340 nm , the latter being identified in Table F as smoke B and llquid smoke composition B. I'he liquid smoke composition B was made Erolll smoke B (Charsol C-lO) by a solven-~
extraction method which was perEormed in a mannericlentical to the extraction of Example I.
Several non-fibrous frankfurter size gel stock casings were treated with the neul:ralized (pH
5.0) aqueous liquld smoke compositions E3 and E~
prepared in Example ~ by applying the liquid smoke solutions to the external su-rfaces of the casings.
Similarly, gel stock casings were treated by app:Lying neutralized as-is smoke B and tar-depleted smoke composition B. The liquid smoke loading was about lO mg./in.2 (1.55 mg/cm2) casing surface in each instance.
The applicator was a device which uniformly distributed the aqueous liquid smoke solution around the casings and comprised two main parts: the liquid smoke applicator and the smoothing unit. The smoke applicator consisted of a stationary foam disc mounted such that liquid smoke entered at the outer edge. Tiny flexible plastic tubes conducted the liquid to the center core where the inflated casing was passed through. The foam disc flexed with casing sizes, thereby maklng it suitable for a range of casing cross-sectional areas. Because the liquid smoXe application is not precisely uniform, a rotating smoothing device was used immediately after the applicator. It comprised a rotating foarn disc with a core size suitable for the casing size being processed. The disc was driven by an air motor at 200 to 250 rpm~ Excess liquid smoke from the applicator and Erom the smoothing device was collected in a common sump and returned to the applicator inlet. The treated casings were mo~ed through a point - support type assembly to and through a drying section. The aforedescribed coating and ca~ing movement assembly is not part of the present invention but is claimed in previously re-Eerenced copending applica-tion No.
40l525-8 ent;tled "Liquid Coating Method and Apparatus 1l .
The treated casings were dried at ~0C to a water content of 1~ weight percent. The casings were then conventionally moisturized to 14-18 weight percent water, and shirred. The levels of the smoke compositions, -the phenols. carbonyls and total acid content present in the treated casings are shown in Table F. The total acid conten-t of the casings was measured by the steam dis-tillation titration procedure discussed hereinafter. Measurement of phenol and carbonyl con~ents in smoke treated casing ;s determined by procedures which are also discussed hereinafter.

l~g6-1 ~'7 V
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D-1289~-1 -5~

One embodlment of the tar~depleted smoke colored and smoke flavored casing o ~his invention may be characterized as a casing having a tar-depleted smoke coating which has less than one-half the phenol content (on the basis of weight per unit area of trea~ed casihg surface) that a casing has when coated with the tar-containing aqueous liquid smoke composition from which the tar-depleted aqueous liquid smoke was derived. The Table P data are specific examples in which the casing of this invention coated with tar depleted liquid smoke composition A had only about one-third the phenol content of the c~sing coated with partially neutralized ~ar~containing liquid smoke solution A. Similarly, casing coated with tar-depleted liquid smoke composition B had less than about one-fourth the phenol content of the casing coated with partially neutralized tax-containing liquid smoke solution R~
Because of the nature of these expèriments, the phenol reduction in the liquid smoke (Table E) and the phenol reduction in the coated casing tTable F3 are no~ proportionate. As in the case of ~able F, no conclusion can be drawn from my work with respect to the effect of this invention on carbonyl content or acid content of the casing.
Examples III and IV show the treatment of non-~ f ibrous cellulose casing by the method of this invention when using the substantially neutralized aqueous liquid smoke composition A of E~mple I with a peelability enhancing agent.
. .
EXAMPLE III
___.__ Several non-fibrous frankfurter size casings were treated as in Example II (Royal Smoke ~53~ ~ 3''~

AA - deriv~d solutions and methylene chloride extraction of tars), except that a solution containing propylene glycol, mineral oil, a polyoxyethylene sorbitan ester (commerciall~
designated as ~Tween sn~ and purchased from Atlas Chemical Industries)~ and 0~85 weight percent sodium ~ carboxymethyl cellulose ~'CMCn) was thereafter spray coated on the inte~ior surface of the casing during shirring at a delivery rate of 3.5 mgs/sq. in. (0.54 mg/cm2) casing surface to improve the peelability characteristics of the casings. The pH of the a~ueous liquid smoke compo~itions (liquid ~moke compositio~q A of Example I) used in the~e experiments was adjusted by the addition of a ~0~
NaOH solution to achieve a p~ of 3.2 or greater as shown in Table G .
Table G
~H Adjustment of Solvent Extracted Liquid Smoke ~ Solution pH
2~ CMC - 8 Untreated control CMC - 9 Sample E2 (pH ~.4) CMC ~ 10 302 CMC ~
C~C - 12 5~0 25 CM~ - 15 5.1 ` CMC - 13 6~1 CMC - 14 7.0 The tar-depleted smoke colored casing samplé~ of Table G were stuffed with a high collagen content meat emulsion having the formulation of Table El~ The stuffed casings were 1289~-1 then psocessed by the conventional steps of cooking, cold water showering and chilling, but without the conven~ional s~ep of smoke treatment~ Proce~sing conditions were sufficient to cause the transfer of smoke color, odor and flavor constituents from the casing to the encased frankfuters. The casings were peeled from the finished fxankfurters on a High Speed Apollo Ranger Peeling Machine, and Table I
shows that these casings peeled 100~ where the pH
was at least 4.1. This means that all frankfurters were separated from their casing at machine peeling speed without mechanical jammin~ of the peeling machine and without scarring of frankfurter surface. Table I also shows that each of the samples had generally superior colorimetric values as compared with ~he control sample CMC-8. All samples showed superior darkness (the nL~ value), but Sample CMC 14 had lower redness (the ~a~ value~
due ~o a relatively high solution pH of 7Ø
Frankfurters processed in accordanc2 with this invention have demon~trated an acceptable smoke flavor~
Table ~
Frankfuxter Formulation 25 ~Lredients ~r~
Beef Chuck 9.9B
Beef Tripe 7.26 Beef Shank 7.26 Beef.Cheek 7.26 30 Regular Pork 13.61 Water 9.98 Table H (co--n---t2-Frankfurter Formulation .
Insredients W~_I
BSalt 1.13 5 _ Seasoning ' 0 45 Sodium Nitrite (Prague Powder) 0.11 Colorimetric values in Table I were obtained using a Gardiner XL-23 Colorimeter with a 1 cm aperture opening standardized with a white plate, all in accordance with the standard operating procedures described in the ins~ruction manual for the Gardiner XL-23 Tristimulus Colorimeter, which is commonly used in industxy for the measurement of color.
Three loca~ions on each of 10 frankfurtere from each t~eatment were selected for reading~. Reading locations were approximately 1 inch (2~54 cm) from each frank end and in the middle. Colorimetrlc "L"
and "a n values were coilected.

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1}12896-1 73,'~

,~
EX~MPLE IV
Non-fibrous frankfur~r size gel stock casi~gs were treated with tar-~eple~ed liquid smoke composition E2 of Example 1, and then the inner surfaces thereof were coated with various ~ peelability enhançing agents. The peelability enhancing agents were various types of wa~er soluble methylcellulose ethers sold by the ~ow Che~ical CompanyO The particular methylcellulose ethers used with the various samples are listed in Table J.
These casings were then stuffed with high collagen meat emulsion as ln Example II~. The stuffed casings were processed and peeledl and the colorime~ric and peelabili y data for the resulting frankfur~ers is summarized in Table I as "MC"
samples. All samples demonstrated relatively good colorimetric ~alues. The samples also showed improved peelability compared to sample CMC-9 which was prepared without a peelabili~y enhancing agent.
~0 The impsoved peelability with low pH (2.4~
tar-depleted liquid smoke may be related to the non-ionic character of ~he methylcellulose ethers.
Table J
Sample No. Type of Methocel 25 MC - 23 K-3 (hydroxypropyl methylcellulose) (methylcellulose) MC - 25 E-5 (hydroxypropyl , methylcellulose) MC - 26 ' A~15 (methylcellulose) MC - 27 K-100 (hydroxypropyl methylcellulose) ~58-Summarizing Examples III and IV, Table I
shows that non-fibrous cellulose casings trea~ed with ~he tar-depleted aqueous liquid smoke composi~ion in accordance wi~h this invention should S also be treated with peelability enchancing agents.
The Table I data also show th~t frankfurters processed in non fibrous cellulose casings treated with a tar-depleted agueous liquid smoke composition in accordance with this invention have darker and redder surface colors than the frankfurters processed in the untreated casing, CMC-8.
Objective criteria bave been used for comparison o the protPin staining (color development) ability of the tar-depleted aqueous liquid smoke composition of ~his invention with the tar~containing liquid smoke from which it is derived. These criteria include the ~Staining Power" as applied to the liquid compositions ~hemselves, and ~he ~Staining Index n as applied to the coating on the tubular food casing. In each instance, the tested embodiments o~ this invention demonstrated substantially the same staining ability as the original tar-containing liquid smoke, yet the tar content had been reduced to a level such that the heretofore experienced tar problems had been eliminated. 5taining index is a reliable ~riterion for measuring the color development ability in GaSings of this invention which are freshly made~
but as he-einafter discussed, staining index should not be used wi~h aged casi~g. The procedure used for measuring staining power.and staining index is .discussed below.' Stainin~ Power and Staininq Index Procedure This procedure has as its basis the reaction encountered in meat processing in which the 1~896-1 3'~
-59~

meat pro~ein reac~s with the smoke components imparting a de~irable dark smoked col3r to the.
product. To quantify this staining or darkening power, the unknown smoke or smoke products are reacted with a specific amino acid (glycine) under _ acidic conditions at 70C for'thirty minutes. The absorbance of the solution is measured at 525 nm.
This procedure an be run on liquid smoke or liquid smoke treated casing with reproducible results. The detailed procedure is as follows.
I. Prepare a 2.5~ solution of glycine in 95 acetic acid.
(a) Dissol~e 12.5 g of glycine in 25 ml of water in a 500 ml volumetric flask.
~dd enough glacial ace~ic acid to facilitate the dissolution.
~b) Dilute to the prescribed level with glacial acetic acid.
II. In the case of liquid smoke analys~s, weigh into a 15 ml test tube vial, 15-20 mg ( 0.1 mg~ of the liquid smoke to be evaluated, or III. In the case of ~moke treated casing analysis, punch,out four double thickness discs from the test casing to yield a casing area o 2.0 in2 (12.9 cm2) for the eigh~ discs.
(a) If the casing is shirred, inflate a section with 10 psi (68,900 Pascals~
air to smooth the surface~ Collapse the casing by ~rawing it over a hard surEac~, punch out ~he discs and add them to the vial.
IV. To the vials containing either the liquid smoke or the treated casing, add 5~0 ml of the 2.5% glycine/acetlc aci.d solution.

128~6-1 -60~

V. Cap the vials, hand shake to assure contact of the s~mple, and place in a 70C oven or constant temperature bath for thirty minutes D
VI,. Measure the absorbance at 525 nm for each _ solution using the glycine reagent as a blank.
V~ he absorbance is ~eported as the staining power of the smoke or the staini~g index o~
the smoked casing.
The numerical values for Staining Index as summarized in Table K indicate the absorbance pe~ 2 square inches (12~9 cm of casing surface;
The staining power represents the ability of a li~uid smoke quantity to develop a certain absorbanoe or color under the 6taining index procedure, i.e., units of absorbance per mg. of liquid~ In these tests the liquid smoke composition loading on tbe non-fibrous cellulose food casing was

6.9 mg/in2 1.1 mg/cm~ of casing surface.
Staining Power values were determined for the same four liquid compositions listed in Table E, and staining indices were measured on the coated casing listed in Table F. ~he results of these protein 5 staining tests are summarized in ~able K.
It should be noted ~hat in the afo~ementioned experiments in which tar~depleted liquid smoke compositions were neutrali2ed after solvent extraction, neutralization was performed without controlling the temperatuxe of the aqueous solutlon during neutralization. The heat of solution substantially increases this temperature to a level as high as 55-60C ~rom an initial temperature on the order of 20C. It bas been 12896~1 discovered that the s-ta;ning power of the resulting at least partially neutralized aqueous l;quid smoke is somewha-t diminished because of the elevated temperature, and this diminishment may be partially avoided by maintaining the temperature below about 40C. during neutraliza-tlon. When such controlled tempeeature neutralization is practiced, the staininq power does not decline to nearly the same extent~ and this discovery is described and claimea in my previously referenced copending application No. 412653-0 entitled "Tar Depleted Liquid Smoke Tre~tment of Food Casings". filed contemporaneously wi-th this applica-tion.
Another advantage of combining the present inven~ion with -the contr~lled temperature neu~ralization oE the aforementioned application is that the amount o~ required solvent may be minimized. That i6, by first neutralizing the as-is liquid smoke under controlled temperature conditions, the tar precipitate is formed and a tar-depleted supernatant liquid is then contacted with a solvent in accordance with -the present invention for further tar depletion. This sequence has been used in experiments similar to those reported in Tables F and F, and the results of same are included in Table K as sample K5 (tar-^deple-ted liquid smoke) and sample K10 (casing treated with tar-depleted liquid smoke).
It will be observed from Table K that the S-taining Power and Staining Index Eor these samples are the highest values of the neutcalized tar-depleted samples, so tha-t the sequence of controlled temperature neutralization -Eollowed by solvent extraction represents a preferred embodiment of thi~ invention.

ë>~-a ~62-Table K
Prote in ~ta i n~ Abil i~
Smoke Sa~ple Staining Power Source No. Smoke Descrip~ion _ Absorbance/mq El Kl As-is liqui~ smoke A
(pH 2.4) ~Sample ~1) 0.034 E2 E~2 Tar-depleted aqueous liquid smoke composition A
(Sample E2) E3 K3 As-is liquid smoke A after uncontrolled temperature neutralization ~pH 5.0) 0.024 E4 B~ Tar-depleted aqueou-~ liquid smoke A ~fter uncontrolled temperature neutralization ~P~ 5-0) 0.024 K5 Tar~depleted a~ueous liquid smoke A extracted after controlled temperature neutralization (pH 5.0) 0.026 Casing Sample Staining Index No~ Casing Absor~c~ 2*
R6 (as derived from Sample Rl) 0-47 K~ (as derived from Sample R2~ 0~46 K8 (as derived from Sample K3) 0.33 Kg (as derived from Sample X4) 0.33 Klo las derived from Sample ~5) 0.36-0.41 *Absorbance/12,9 cm2 ~i 3 EXAMPLE Y
Another series of tests was performed which demonstra~es the difference between as-is tar-containing -liquid smoke and the tar-depleted liquid smoke of this invention, in terms of c~llulose casing haze.
Samples of casing with each type of liquid smoke incorporated therein were irNmersed in waterr During this period, the incorporated tar components are insolubilized by the water. In the case of the tar-depleted samples, no incompatibility was ~easured, but with the tar-containing samples the tar precipitated in or on ~he casing, and water incompatibility in the form of a cloudy haze in the casing was measured quantitatively~
More specifically, Royal Smoke AA liquid smoke was applied in a quantity of a~out (1.55 mg/cm2) lO mg/in2 to ~he external surface of a 21 mmO diameter cellulose casing having a carboxymethylcellulose InCMCa) - based coating on the internal surace for improved peelability. For the samples produced by practicing this invention, the as-is liquid smoke was first contacted with methylene chloride liquid solvent in a volume ra~io of lO:l liquid smoke solution to liquid solvent.
Af ter mixin~, the solution was allowed to stand for a period of 12 to 16 hours to form the two layer~, and.the separa~ed tar-depleted liquid smoke upper layer was partially neutralized to a pH of 5.0 and incorporated on the cellulose ca~ing external surface by the Example III p.rocedure.
The treated casings were shirred and 36 inch (91.4 cm~ long samples were taken randomly from a deshirred ~tick, inflated with air to minim~ze 12~96-l J a~
~64-shirring wrinkles~ and immersed in 200 ml of deionized water. Immersion time was at least one hour but not mor~ thasl three hours, the criterion being soaking for sufFicient duration to achieve complete water penetration of the casing wall.
After blotting the samples ~ry, casing haze was mea.~ured using the general proced~re outlined in ASTM Method D 1003, Volume 35, ~Haze and Luminous Transmittance of Transparent Plastics" (1977)~
The re~ults of these tests are summarized in Table L as follows-Table L - Casing Haze ~y~e Casin~ No. Determinations Haze Range Ave Ha2e Untreated (control~ 32 6.0-9.7~ 7.9 Tar-Depleted Liquid Smoke 28 5.4~8.7% 6.6%
Tar-Contalning Liquid Smoke 32 8.5~13.1~ 10.7%

~66-It is apparent from Table ~ that the average haze for the as-is tax-containing liquid smok~ treated cellulose casing, i~ substantially higher than the average haze for the tar depleted liqu.id smoke treated cellulose casiny of this invention, such that the laEter is only about 61.6%
of the former. Average haæe values increase with increasing diameter because of the thicker casing wall. The absolute value for average haze also depends on the total acid content (or absorption power as discussed hereinafter) of the particular smoke and the amount of smoke incorporated in the casing (or absorption index also as subsequently discussedJ, but in general, the avesage haze for the cellulose casings of this invention are substantially lower than the average haze or cellulose casings treated with as-is liquid smoke, even though their coloring and flavor developing capabilities for encased foodstuffs are about the same when prepared under equivalent conditions.
This rela~ionship demonstrates ~he chemical and functional difference between the tar-depleted liquid ~moke treated cellulose casing of this invention~ and the as-is,li~uid smoke treated casing~
The haze test is only useful in charac~erizing the cellulose casings and not the fibrous casing of this invention. ~his is because fib~ous casings are inherently opaque and have a very high average haze, e.g., abou~ 97~5% for untreated fibrous casingsO
: EXAMPL~ VI
A ~eries of tests was per~ormed on aged casings of this invention which demonstrates that 128g6-1 even ~hough ~he s~aining index of the tar-depleted liquid smoke treated casings declines significantly ~rom the staining indices of freshly prepared casinys, surprisingly, the stuffed food product made by using the aged casings has smoke color equivalent _ in colorimeter value to product produced with fresh casing.
These aging tests included casings treated ~ith as-is tar-containing liquid smoke under substantially identical conditions, and the staining index did not decline for such casings nearly to the extent that the staining index declined for the tar~depleted liquid smoke ~reated casings of this invention. This comparison demonst~ate~ the chemical difference between the two types of casings.
In these tes~s Royal Smoke AA liquid smoke was applied ~o the external surface of 21 mm.
diameter cellulose casings having a CMC-based coating on the internal surf~ce for improved peelability. For the sample produced by practicing this invention, the as-is liquid smoke was first contacted with methylene chloride liquid solvent in a volume ra~io of 10:1 liquid ~moke ~olution to liquid solvent. After mixing, the solution was allowed to stand for a period of 12 to 14 hours to form the two layers. The separated tar-depleted liquid smoke upper layer was partially neutralized to a pH of 5 and incorporated on the cellulose casing external surface by the Example III
procedure. Half of the casings were stuffed with a high collagen-content frankurter meat emulsion very similar to the Table I formulation~ and processed by the conventional steps oP cooking, cold water showering and chilling, but without conventional smoke treatment. The other half oP the casings was 128~6-1 3'~1.3~ ~
-6~

aged as set forth in Table M, and then ~hey were used to produoe frankfur~ers in ~he same manner.
The results of these tes~s are summarized in Table M. The colorimetric values were obtained with the same equipment used in Example III and by the same _ procedure described in connec~ion therewith.
It should be understood that the Table M
data should not be compared ~uantitatively, because the initial staining indices (~Fresh 5.I.n) are different and different aging conditions were usedO
~owever, the da~a doas ~ualitatively support the general relationship that stufed food p~oduct made by using aged easings has smoke color which is unaffected by ~he casing age, notwithstanding the fact that the staining index of the casing declines with age.
EXAMPLE VII
A further series of ultraviolet absorption spectroscopy tests was performed using cellulose food casing treated with tar-depleted liquid smoke according to this inven~ion, and the tar-containing as-is liquid smoke. These tests demonstrate the substantial difference between the two types of casings. The tests invoived three different types of wood-derived liquid smokes: Charsol C-12, Royal Smoke AA, and ~oyal Smoke B, and in each instance the casing was 21 mm. diameter cellulose casing having a CMC-based coating on the internal surf~ce for improved peelability. For Charsol C 12, the as-is liquid smoke was first contacted with methylene chloride liquid solvent in a volume ratio of 10:1 liquid smoke solution to liquid solvent and then allowed to stand for a period of 12 to 14 hours. For Royal Smoke AA, the as-is liquid smoke l2a~6-l ~-~9-was first conta~ted with methylene ~hloride liquia s~lYent in a volume ratio of 10 :1 liquid smoke solution to liquid solvent and ;hen al].owed ~co stand for a period of 12 to 14 hours. For Royal Smoke B, the as-is liquid smoke was first contacted with methylene chloride liquid solvent in a volume ratio of 15 :1 liquid smoke solution to liquid solvent ans~
'chen allowed to stand for a period of 12 ~o 14 hours. In each instance, the resulting two layers were separated and the upper layer was the tar-depleted liquid smoke having a pH of 2., 4 which was used to treat the cellulose casing external surface in ~he manner described in Example III. The same treatment procedure was used with the three types of as-is liquid smokes also at a p~ of 2. 4.

1289~-1

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The liguid smoke-treated casings were ~hen subjected to the following procedure to obtain liquid samples suitable for obtaininy the ultraviolet a~sorption spectrum in the 350 to 210 nm. range;
~a) A 100 in2 (645 cm ) sample of liguid smoke treated casing w~s submerged in 200 ml of anhydrous methanol for a period of about 1 hour a~cl then removed.
(b) Depending on khe liquid smoke loading, ful~her dilution must be made for compati~ility with the UV scanning equipment. In these instances the liquid smoke loading was 10 mg/in2 (1.55 mg/cm2) casing, and the solution used for scanning comprised 4~96 ml. of methanol and 0.10 ml. of the extract.
(c) The W spectrum was recorded in the 350 to 210 nm. range with the following format-2 second response/2 mm slit, 10 nm~/cm. chart, 50 nm/minute scan speed, and 0-200% transmittance scale.
In order ~to measure ~he absorbance primarily due t~ tars present in the liquid smoke~
the spectrophotometer was zeroed using an extract solution containing the lowest possi~le tar content. For any particular type of liguid smoke, this was an extracted and neutralized (pH 5.0) smoke treated casing extract sample. Once zeroed in this manner, any additional ab-~orbance in the UV spectrum was.a quan~itative measure of the ~arry components present.
The results of these ultraviolet absorption tests are plotted in the Fig~ 9 graph with the Charsol C 12 samples shown as solid lines, the Royal Smoke AA samples as dash lines, and khe Royal Smoke B samples as dash~dot-dash lines. The greater than .

zero transmittance recorded in Figure 9 is a f~nction of ~he machine blank used in these particular experiments. Inspection o these curves reveals that the greatest difference between the tar-depleted sa~ples (upper cur~es~ and the - t~r-containing samples ~lower'curves~ occurs at abo~lt 210 nm. wave length, although there is a substantial difference over the entire scanned range of wave lengths. The ultraviolet absorbance and percent light transmittance values at 210 nm. wave length a~e summarized in Table N, and show that tbe tar-depleted liquid smoke treated cellulose casings of this invention have an ultraviolet absorbance at 210 nm. waYe length which is reduced by a~ least 90 compared to the corresponding tar-containing as-is liquid smoke trea~ed casing having ~he same total acid content.

~73-Table N
Ultraviolet Comparisons at 210 nm Wavelengt~
for Smoke Extracts from Sm_ e-Treated Casings Percent Type of Transmittance Reduction in Liquid Smoke ~ ~bsorbance Absorbance*
Charsol C-12 Tar-Depletedabout 100 zero about 100 Tar-Contalning 14 0.854 --Royal Smoke AA
Tar-Depleted86 0.066 95 Tar Containing 6 1,222 --Tar-Depletedabout 100 ~ero about 100 Tar-Containing 6 1,222 --*Percent reduction in W Absorbance of tar-depleted liquid smoke compared to UV Absorbance of tar-containing liquid smoke.

3~ i~

EX~MPLE VIII
All of ~he previously described tubular food casing treatment e~periments involved nonfibrous cellulose casings, but the invention is S also useful in treatment of cellulosic fibrous casings. In this experiment,~the tar depleted liquid s~oke was prepared from Royal Smoke AA as-is liquid s~oke solution by the methylene chloride solvent extraction method of E~ample I, but without p~ adjustmen~. Fibrous casing sto~k of about 6.3 inch (16 cm) flat width was then treated with tar-depleted liquid smoke in a process substantially as shown in Figure 1. The estimated tar-depleted liquid smoke solution load~ng on the casing wa~
15 about 20 mgs,/sq.in. (3.1 mg/cm2) of casing surfaceO A sample of this liquid smoke tre~ted casing was ~uffed out with a bologna meat emulsion, and then processed in a conYentlonal manner tc produce finished bologna, except that no smoke was applied in the smokehouse. The bologna showed good smoke color, odor and flavor when compared with a control bologna processed at the same time in the same smokehouse within a casirlg which was not treated wi~h any liquid smoke.
In a preferred embodiment of this invention, the tar-deple~ed liquid smoke composition is prepared from a tar-containing aqueous liquîd wood smoke solution having a total acid content of at least about 7 weight %, and most preferably a total acid content of at least about 9 weight ~.
Total acid contsnt (also reerred to as total acidity) is a qualitative measure o~ the tar content and staining pswer (previously d~fined) of as-is liquid wood smokes used by manufacturers. In general, higher total acid content means higher tar content. The same is true of the total ~olids 12~96-1 3~ >~

content of as~is liqu.id smoke. The procedures used by liquid wood smoke manufacturers to determine total ac~d c~ntent Itotal acidity) and ~o~al solids are as follows:
Determination of Total Acid Content for Tar-Containin~ Liquid Smoke -1. Weigh accurately about 1 mlO of liquid smoke (filtered if necessary) in a 250 ml. beaker.
2. Dilute with about 100 ml. of distilled water and titrate with standard 3.lN
NaO~ to a pH of 8.15 (pH meter)O
3. Calculate the total acid content as per cent by weight of acetic acid, using the follo~ing conversion:
1 ml. 0.1000 N NaO~ = 6.0 mg. HAc etermination of Total ol ds 1. Pipet about 0.5 ml. of liquid smoke on a tared 6 cm aluminum moistu e dish fitted with ~ dried Whatman No. 40 filter paper disc, and weigh accurately. The liquid smoke should be clear~ and filtration is used to in~ure this condition.
2. Dry for two hours at 105~C in a forced draft oven~ or for 16 hours at 105C
in a conventional oven.
: 3. Cool to room temperature in a desicca~or and weigh.
4. Calculate the total solids as per cent by,weight of ~he liquid smoke.
As will be discussed hereinafter, this dilu~ion-titration procedure as also used for measuring the total acid content of the tar depleted liquid smoke composition which has not been at least partially neutralized.

~61 :~ 7~
-7~~

Table 0 lists the m45t commonly used and commercially available tar-containing aqueous liquid wood smokes along with their manufacturer-reported Total Acid Content (~otal acidity)~ Total Solids Content, Staining Power 7 and percent light transmittance at 590 nm. are also reported for comparison. Xt will be noted frQm Table 0 that the as-is wood smoke solutions with total acid content values les~ than about 7 weight ~ have high transmittance values above 50~ and low staining power~ Their tar content is so low that their water compatibility is high. Accordingly, there is no need to remove tar from such wood smoke solutions in accordance with this invention. Also, their staining powers are so low ~hat they are not capable of performing the same smoke coloring and smoke flavoring function as the tar~depleted aqueous liquid smoke compositions of this invention. It should however be recognized ~hat such low-tar content as-is liquid smoke solutions may be concentrated as for example by evaporation, and the so-concentrated liquid smoke solution then may acquire ~he characteristics of a tar-c3n~aining liquid smoke which c~n be advantageously treated in the manner of ~his invention. That is, such concentrated tar-containing liquid smoke acquires higher total acid content, total solids, and staining power.

. . .

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~78-It will be reealled that the aqueous liquid smoke solvent ex~raction treat~ent aspect of ~his invention requires a liquid smoke solution ~o liquid solvent ~olume ratio between about l:l and 65:1~
Figure lQ illustrates that ~o obtain the preferred light transmittance of at least SO~ at 594 nm, the ~ratio is a function of the particular liquid solvent to be used. Figure lO illustrates that the practitioner also needs to consider the particular type of a5-is liquid smoke in the achievement of the desired per~ent light tr~nsmittance.
More particularly, Fi~ure 10 is a yraph showing percent light transmittance at 590 nm. as a function of the as is liquid smoke to solvent volume ratio fox several of the liquid smokes listed in Table O. Royal Smoke A~ is ~hown as ~ dash line, Charsol C-3 as a dotted line, Charsol C-12 as a solid line, Royal Smoke B as a dash-dot~dash line, and Charsol C-lO as a dash-dot-dot dash line. The liquid solvent is methylene chloride in all of the experiments summarized in Figure 10, and th~ sa~e general relationship exists with respect to other liquid solvents sui~able for practice of this invention. This Figure shows that to achieve a particular level of percent light transmittance with a particular solvent, the practitioner may select a liquid smoke having relatively high absorptive power and total acid content~ and us~ a relatively lar~e quantity thereof (i.e., a relatively low smoke to solvent ratio). Alterna~ively one may use a liquid smoke having relatively low absorptive power and tota~ acid content, and use a relatively small quantity thereof (i.e., a relatively high smoke to solvent ratio)O The Figure also shows tha~ for a particular Qmoke to solvent. ratio ~the same ~uantity 12896-l 7~

o liquid smoke), the practitioner will obtain a relatively highe~ percent iight ~ransmittance with a liguid smoke having relatively low absorptiYe power and total acid content.
Figure 10 also shows that the upper limit of 8uitable liquid smoke to~solvent ratios for practicing this invention (S5:1) is based on the rat.io suitable for the liquid smoke o lowest absorptive power (0.3 at 340 nm wave length) and total acid content, to achieve the preferred standard of at least 50~ light kransmittance at 590 nm. Among the liquid smokes included i~ the ~igure, Royal Smoke B has the lowest acceptable values and its curv~ indica~es a transmittance of about 50~ at a liquid smoke to solvent ra~io o~ about 65-1. It should also be noted that the Charsol C-3 curve demonstrate~ its high compatibility with water without any solvent (98% light transmittance~ and at all solvent ratios. Accordingly, the present invention is not useful with as-is Charsol C-3, noting its low absorptive power ~0.12) and low total acid content ~3.6%).
In general, when the as-is liquid smoke solution has a total acid content between about 7 and 9 wto ~ ~ the selected liquid solvents are effective in a volume ra~io between about 30:1 and 65:1 of li~uid smoke solution to Rolvent.
Similarlyy when ~he as-is liquid smoke has a total acid content between about 9 and 11~5 w~. ~, the solvents are effec~ive in a volume ratio between about 15:1 and a~out 30:1 of liquid smoke solution to solvent. ~nd-when the as-is liquid smoke has a tokal acid content greater than about 11.5, the volume ratio for effec~ive extraction o the tars is between about 7:1 and about 25~1 of liquid smoke solution to solvent.
Another series of experiments was performed which illustrate~ the basis for the lower limit of liquid smoke to liquid solvent volume ratio in the _ practice of this invention - about 1:1. The solvent was methylene chloride, and Figure 11 shows the effect of decreasing smoke to solvent ratios for Royal Smoke AA Idash line), Charsol C-l~ (solid line), and Charsol C-10 ~dash-dot-dot-dash line)O
These data ~ho~l that with a smoke to solvent volume ratio below about 1:1, the Staining Power of the tar-depleted liquid smoke diminished to a level so low as not to be useful.

Absorptive Po er It will be recalled ~hat both the staining power and staining inde~ mea~urement prvcedures involve chemical reaction, and apparen~ly for this reason the values measured at ambient temperature decline under elevated temperature aging conditions. As demonstrated in Example VI, this decline is not an accurate indication of the smoke color in st~ffed food product using casings aged after tar-deple~ed liquid smoke treatment.
Under these circumstances, additional measurement procedures no~ involving chemical reaction have been used in this invention to determine the coloring capability of liquid smoke and the liquid smoke-treated casing. Thie measurement procedure for liquid smoke is termed ~Abs~rptive Powern and the measurement procedure for liquid s~oke-treated casing is termed "Absorptive Index.

In the procedure for measuring absorptive power, lO mg. of liquid smoke ~either tar-containing liquid smoke or ~ar-depleted liquid smoke~ i~ placed in a disposable vial and 5 mlO of ~ethanol is added thereto. The two components are mixed b~ inverting - the vi~l, and the ultraviolet absorption value of the mixture is then measured at 340 nm. This particular wave length is selected ~ecause spectroscopy measurements with many liquid smoke~
indicate greatest linearity in this wave length region~ Absorptive power measurements for various as-is liquid smokes are included in Table 00 A plot of these absorptive power measurements as a function of total acid content or total ~olids content reveals an approximately linear relationship.
It should be noted that whereas tar content i5 a significant contributor to the absolptive power measurement, I have discovered that tar only contributes to the staining of food in a minor way, if at all. Thus, in commercially avallable as is smokes, absorptive power includes a measurement of tar content and the coloring constituents such as carbonyls, phenols and acids. ~his mean~ that absorptive power of as-is smokes and tar depleted smokes may be used to ra~k them by ~moke coloring ability. ~owever, absorptive power of ~s-is liquid smoke cannot be numerically compared with the abssrp~ive power of tar-depleted smokes of this inven~ion because of the absorptive efect of tars.
Unlike staining power~ the absorptive power of liquld smokes does not decline with aying.
EX~MPLE IX
A seri~s of absorptive power measurements was performed on various ~ar-depleted liquid s~okes 1289~-l -82~

of this invention, using methylene chloride as the solvent. In each ins~ance the as-is liquid smoke was fir~t neutraliæed by the addition of sodium hydroxide flake and the neutralization temperat~re was conkrollably maintained at 10-15C to remove a -first tar portion. The resûlting liquid smoke with its partially depleted tar con~ent was then contacted with methylene chloride in order to remove a second tar portion~ The liquid extraction procedure was the same as described in Example I, and the liquid smoke to solvent volume ratio was 10:11 These measurements are summarized in Table P~

~L~ 3 ~
~83 -Table P
P.bsorptive P~wer Type of Li~uid Smoke As-Is Tar Depleted Royal Smoke AA 0 . 51 0 . 26 ~0 . 26~ *
Pcoyal Smoke A 0.45 0O30 (0.20)*
~oyal Smoke 1~ 0.35 0.25 (0.15) *
Charsol C-10û.40 0.33 Charsol C-60.22 0.17 (0~17) *
Charsol C-30.11 0.10 *Values in parentheses were obtained from different batches of liquid smok~O

~8~

Table P should be interpreted in light of the preceding discussion relating to ~he effec~ of tar content or liquid smoke absorptive pcwer.
Inspection of Table P reveals that the absorptive power of a tar-depleted liquid smoke of ~his .invention is generally lower ~han the absorptive power of the tar-containing as-is liquid smoke from which it is derived~
Table P also demonstra~es that ~he tar-containing liquid smokes useful in the practice of this invention have absorptive power values of at least about 0.25 and that tar-containing liquid smokes such as Charsol C-3 which are not useful in the as-is form have absorptive powers below 0.25.
The absorptive power o~ ~he tar-depleted liquid smoke composition of this invention must be at least about 0.15 in order ~o obtain acceptable ~moke color on a foodstuff produced in a smoke treated casing of this inventionO In a pref2rred embodim~nt the absorptive power of the tar-depleted liquid ~moke composition is at least 0.25. It will be recall~d that Figure 10 demonstrates that Char~ol C-3 has a very high light transmittance of about 98% because of its low total acid content and low total solid~
and/or tar content~ and solvent extraction treatment doe~ not significantly affect its light transmittance.
Absorptive Index In the procedure for measuriny absorptive index, 2 ~quare inches ~12.9 CM2) o liquid .smok~vtreated ca~ing are cut out after drying, and placed in lO ml. of methanolO After l hour of soaking time, the methanol has extracted all of the smoke components out of the easing, and the 1289~-l --8so ~ltraviolet absorption value of the resulting smoke component-con~aining methanol is determined at 340 nm. As wi~h the absorptive power measurement~ a 340 nm. wave length was selected because spectroscopy measurements with many liquid smoke extracts from smoke treated casings indic~te greatest correlation with smoke loading in this region.
ÆXAMPLE X
A series of absorptive index measurements was made on casings using three diferent types of tar-deplet~d liquid smoke prepared in accordance with this inven~ion with neutrali2ation to a pH of 5Ø The liquid smokes were applied at different loadings to the exterior surface of non-fibrous frankfurter size gel s~ock casings in the Example II
manner. The results of these experiments are summarized in Figure 12~ with Royal Smoke AA~derived liquid smoke shown as a dash line, Charsol C~12-derived liquid smoke shown as a solid line, and Royal Smoke B-derived liquid smoke shown as a dash~dot dash line. This figure permits the practitioner to first select the desired extent of smoke color ~nd types of smoke in terms of absorptive index, and ~h~n determine the required loadiny of a particular tar-depleted liquid smoke onto the casing to achieve this smoke color. The correlation between smoke color and absorptive index is illu~trated in the following ~xample XI~ In Figure 12, 1 mg/in2 i5 equal to 0.155 mg/cm EXAMPL~ XI
A series of colorimetric tests was performed usiny frankfurters prepared in the manner of Example III in non-fibrous casings treated with various li~uid smokes including those on which Example X is based. The results of these tests ~re summarized in Table Q~

a~
.
Y. ~-~I co o r~
.,, C ~, .~

C X ~
u~ ~ a o C o o o C/~

C
a c: ~ ~ ~
P ~ ~ O ~ ' a X
a ~: ~ a~ a) a? ~ a) o ~ ,w. ~ ,~: ~l Y
:: ~ a~ o a~ o 0 o ~Q
a) u~ ~ v~
o ~ a~ a~ o :, .,, ~ ,~ ~a a~ :~
P. ~ ~J ~ ~J ~ ~J
~ .,, ~ o ~ o ~ o O E~ t~

~ ~ o ~ ~ ~

~ z c~

~ o [n an ~ttempt to quant-lfy the desired llght intensity changes neecled to insure adequate color deve'Lopment, ~L values were determined and are incluclecl in Tsble Q. In this inst~nce, the meat S emu'lsion was 50% beef chuck and 50% regular pork trim, and ~L values were considered too low i~' a 1.4 unit chan~e in light intensity or less, occurred between L values measured on frankfurters produeed withln a non-smoked control casing compared to a liquid smoke treated casing.
Table Q shows that iE the absorptive index is less thRn about 0.2, the smoke loading is 4.0 mg/in (0.62 mg/cm ) or less. This level of smoke loading does not generally give a desired reduction in li~ht intensity to the meat product, i.e., color development is generally considered to be lnsufficient. Based on extrapolation from Sample Nos. 1 and 2, a medium reduction in light intensity for the frankfurter achleved with a liquid smoke loading of about 8.S mg/in2 Sl.32 mg/cm2) on the casing is quite satisfactory for most end uses, so that the corresponding absorptive index of at least 0.4 for the c~sing represents R preferred embodiment of the invention.
I'able Q also shows th~t embodiments of this invention have substantially the same st~ining ability as the original tar-containing liqui~
smoke. Comparison of Samples Nos. 1 and 3 shows th~t the tar content of the liquid smoke h~s very little influence on the staining ability of the liquid smoke. For pract-lca'l purposes, the frankfurter light intensity of 2.9 for Casing Sample No. '1 is suhstantially equivalent to the frankfurter light intensity of 3.4 for Cas-Lng Sample No. 3.
12~96-1 ~.d ~

8~

It ~hould be noted that many factors associated with the food emulsion and processing conditions can affect background color and hence L
and ~L values. For exa~ple, meat derives much of its color from myog~obin6 ~he color associated with myoglobin content of meat is known to be dependent upon chemical reaction of myoglobin and the cure which in turn is affec~ed by processing condi~ions such as temperature, humidity, time and air velocity. Accordingly, the L values in Table Q are only relevant ,or these particular tests~
All of ~he previously described experiments relating to absorptive index were per ormed on either non-fibrous casings of the same diameter promptly after liquid smoke treatment ~nd dryingO
Other tests have shown that absorptive index is not significan~ly ~ffected by variation in a~ing thickness. S~ill other tests have ~hown that absorptive index values for the tar-depleted liquid smoke treated ibrous casings of thi~ invention are about the same as ~he abso~ptive index values for non-fibrous cellulose casing with the same amount of smoke coating. Thus, the broad requirement ~or absorptive index oÇ a~`leas~ 0O2 and the preferred value of at least 0.4 i~ also applicable to fibrous casing. By way of illus~ration, an absorptiYe index of 0.43 was obtained with a fibrous cellulosic casing of 115 mm diameter treated with tar-depleted liquid smoke derived Prom ~oyal Smoke A~ at a loading of 10~1 mgO/in2 ~1.57 mg/cm2) of casing external surface~ The ahsorptive index for the nonfibrous cellulose casing, treated with the same amount of liquid smoke in the same manner, i6 found Prom other tests to be about 0.4.

7~
~8~

EXAMPL~ XII
A series of tests was performed on tar~depleted frankfurter size cellulose casings to demonstrate the minor effect of elevated ~emperature aging on absorptive index. ~, In these tests tar-containing as-is liquid smoke was first neutralized to a pH of 5.0 by the addition of sodium hydroxide flake with the neutralization temperature being controllably main~ained a~ 10-15C. The liquid extraction procedure was the ~ame as described in Example I, and the liquid smoke to ~olvent ratio was 10:1.
Absorptive index measurements were obtained on the tar-depleted liquid smoke treated casing promptly after treatment and drying~ and after storage periods of five and twelve weeks at ambient temperatures. Other samples of the same casing were heated to 100F (38C) and absorp~ive inde~
measurements were obtained at the same time~
intervals. These measurements are summarized in Table R.
Table R

Time and Temperature 25 Initial at 21C 0.52 Five Week~ a~ 21C 0.49 Twe~ve Weeks at 21C 0.49 Five Weeks at 38C 0.54 Twelve Weeks at 38C 0.59 Table R demonstrate~ that aging has no .significant effe~t on absorptive index~ The absorptive index requirements o this invention are to be unders~ood as based on measurements at ambient temperature.

1289~ ~

3~
--~o--In another preferred embodiment of this invention, ~he ~ar-depleted aqueous liquid smoke composition has a total aci~ content of at least about 7 weight percent and most preferably a total S acid content of at least about 9 weight percent.
Total acid con~ent i5 a quali~ative measure of the staining power (previously de~ined) of not only tar-con~aining liquid smokes but also tar-depleted liquid smokes prepared therefrom by the solvent extraction method of this invention. This invention does not require at least ~artial neutralization of either the highly acidic tar containing liquid smoke or the tar-depleted liquid smoke composition, although this may be desirable. I the tar-depleked liquid smoke composition is not ne~trali~ed for purposes of ~his invention7 its to~al acid content is measured by the ~ame dilution titra~ion procedure previously outlined for measuring a total acid content of tar containing (as-is) liquid smoke. If the tar-depleted liquid smoke composition is at least partially neutralized, the total acid content is measured by a ~team distillation recovery-titration procedure. This me~hod is theoretically capable of quantifying the acids such as the acetate and formate, which are formed in the at least partially neutralized tar depleted li~uid smoke composition~ From a reaction standpoint~ the acid percènt in ~he aqueous liquid smoke ~in free or ~alt form) remains constant during at least partlal neutralization. However, the recovery of these acids is only about 70% due to an inability to achieve comple~e azeo~ropic recovery within reasonable dis~illatio~ volumes. At present, a procedure providing quantitative recovery of all 12~96-1 acidic compounds from the tar-depleted liquid smoke regardless o state is not readily available. Under these ci~cums~ances, the results obtained by ~he steam dis~illation recovery-titration procedure are multiplied by a factor of 1~4 for conversion to the ~ same total acid content basis used with tar-containing liquid ~moke. Measurement of total acid, phenol and carbonyl contents in smoke treated casing is determin~d by ~he following procedures.
Determination of Total Acid Content for at least Partially Neutralized Tar-Depleted Liquid Smoke and Treated Casinqs Produced Therefrom __ _ This determina~ion is made from the milliequivalents of sodium hydroxide (NaO~3 required ~o neutrali2e the milliequivalen~s of ace~ic acid (HAc~ which are dis~illed upon acidifica~ion of ~he at least partially neutralized tar-depleted liquid smoke composition or ~reated casings produced from that composi~ion. ~Milliequivalen~ rePers to the weigh~ in grams o~ a subs~ance con~ained in 1 ml. of a 1.0 Normal solution. The procedure is as follows:
1. Weigh accurately 5 gmO of tar-depleted smoke into a ~ared 800 ml. ~jeldahl flask. For casings, ~easure 2~ accurately 100 square inches of casing ~urface.
2~ Add boiling chips and 100 ml. of 2%
fv/v) ~2so4 t4 the flask, the reactisn beiny 2NaAc ~ ~2~4 ~ H~c Ma2S4 3. Place a 500 ml. Erlenmeyer flask containing 100 ~1. of deionized water into an ice bath, and use this water to collect ~he distillate~

'7~

4. Connect the sample-con~aining ~jeldahl $1ask to the steam distillation apparatusO
5. Distill the sample until the distillate voIu~e in the ~ollecting Erlenmeyer flask reaches 500 ml~
6. Titrate 100 ml. of distillate with 0~lN NaOH to an end point pH of 7.0 the reaction being H~c + NaOH ~ Na~ 2~
7. Calculate the measured acid content as weight of acetic acid on the basis that 1 ml. o~ 0.lN NaO~ is . equal to 6.0 mg~ of H~c, so measured acid content in mg. = ml. of titrant x 6Ø
8~ Total acid con~ent = 1.4 x measured acid conten~ in mg,

9. For liquid smoke, express the`value of total acid content in mg. as the wt. %
of the orig.inal li~uid smoke sample.
For casing, express the value of total acid content as mg. of acid per 100 square cen~ime~er of casing surface.
The total acid contents of several tar-depleted liquid smoke compositions of ~his invention have been measured by this steam distillalion recovery-titration procedure, and are listed in Table S. For comparison, the same procedure has been used ~o measure the total acid .conte~t of the aS-is tar containing liquid smoke from which these compositions were derived, and the results are also listed in Table S. It will be noted that the values are quite similar for the same 1~8g6-1 3~'~

type o liquid smoke, whether it be ~ar-containin9 or tar-deple~ed. For example, as-is Royal Smoke AA
liquid s~oke has a total acid content of 11.1~ and in one experiment tar-deple~ed Royal Smoke AA liquid 5 ~ smoke has a total acid content of 11.7~. For further comparison, as-is Royal Smoke AA liquid smoke, as measured by the dilution-titration procedure used by the manufacturer and outlined herein for ~ar-containing li~uid smoke, has also been included in Tabl~ S. This value of 11.4~ is also very similar to the valueæ for Royal Smoke AA
based on the steam distillation recovery-titration procedllre .

~'73~'~
g .~

TABLE S
Total Acid Content of A~-Is and Ta~-Depleted Liquid Smoke Tar Analy~icalTotal Acid Smoke Type Content - MethodContent in Royal Smoke A~ as-is Dilution/
Titration 11~4 n ~ ~ ~ Steam Distillation/
Titration 11.1 Royal Smoke A ~ ~ 10.2 Royal Smoke B ~ n 9.1 Royal Smoke 16 N n 9. 8 Charsol C-12 n w 11.8 Royal Smoke AA Tar- .
Depleted ~ 11.7 Charsol C-12 n ~ 10 . 5 L

Determination of Phenol and Carbonyl Content in Li~uid_Smoke-Treated Casin~s The samples ~re prepared by me~suring and steam distilling 200 to 300 square inches (0.129 -0.194 m2) of casing external; surface, as described ~ in the procedure for determination of total acid content.
The reagents for the phenol determination are prepared with distilled water, as follows:
1. Color solution - Dissolve 100 mg. o N-~,6-trichloro-p-benzoquinoneimine in 25 ml. o ethanol9 and refrigerate7 For the test, dilute 2 ml~ to 30 ml. with water.
2~ Buffer, p~ ~.3 - Dissolve 6.1~45 gm.
of boric acid in 250 ml. of water.
Dissolve 7.45 gm. of potassium chloride in 250 ml. of wa~er.-Dissolve 0.64 gm. of NaOH in gO ml. of water. Mix the three solutions together.
3. 1.0% NaOH Dissolve 1.0 gm. of NaO~
in water. Dil~te to 100 ml.
25 4~ Standard solution - Dissolve 0.200 gm.
of dimethoxy- phenol (DMP) in 2000 ml.
water. Then dilute portions of this solution to provide standard olutions containing 1 ppm, 2 ppm, 4 ppm, 6 ppm, and 8 ppm of DM~.
. The pro~edure for phenol determination is a modified Gibbs method, as described in Wild F, stimation of Organic Compounds, 143, 90-94, University Press, C~mbridge, 1953. In thi.s procedure, the sequence is a~ follows:

~ 1st - In a 25 ml. flask~ mix the four constituents in the order listed:
5 mlO buffer pH R.3 5 ml~ casing di~tillate standard, or ~ater [blank) 1 ml~ l~ NaOH
l ml. dilute color reagent 2nd - Shake~ stopper and place in dark fQr 25 minutes.
3rd Read absorbance at 580 nm.
4th - Prepa~e a standard cu~ve using absorbance as khe ab~cissa and standard concen~rations as the ordinate. Extrapolate concentration of DMP in casing distillates from this curveO
5th - Calcula~e mg DMP/100 cm casing usîng ~he following equation:

p~ ~P(fra~ std Q~rve)x500(d~11u~an~xO~OO~ s lOO~g ~P/lOOall2 ~r~a o ~g ~ e The reagents for the carbonyl determination are.as follows:
l. Saturated solution of recrystallized 2,4-dinitro-phenylhydrazine (DNP~ in carbonyl-free methanol.
2. Concentrated HCl.
3. ~0% Alcoholic XOH ~ Di~solve 10 gm~
KO~ in 20 ml. distilled water and dilute ~o 100 ml. with carbonyl-free methanol.
4~ Standard solutions - Dilute l ml~
2-butanone (methyl-ethyl-ketone) (MEK) ~o 2000 ml. with distilled water.

7~

-g7 - Then dilute portions of this solution to provid~ standard solutions containing 0.8 ppm, 1.6 ppm, 2.4 ppm, 4.0 ppm, and 8.0 ppm of MEK.
The procedure for carbonyl determination is a mo~ified Lappan Clark method as described in the article "Colorimetric Method for Determination of Traces of Carbonyl Compounds~, Anal, Chem., 23, 541-542 (19511. In this procedure, the sequence is as follows:
1st - In a 25 ml. flask, mix the three constituents in the order listed:
5 ml. of 2,4 DNP solution 5 ml. casing distillate, standard, or water ~blank) note- casing distillate may require further dilution.
1 drop concentrated ~Cl.
2nd - Digest the mixture for 30 minutes in 55C water bath.
3rd - Af t~r rapidly cooling the digested mixture to room temperature, add 5 ml. 10~ alcoholic KOH, shake and let stand for 30 minutes.
25 4th - Read absorbance at 490 nm.
5th - Prepare a standard curve using absorbance as the abscissa and standard c~ncentrations as the ordinate. Extrapolate concentration of MEK in casing dis~illate~ from this curve.
6th - Calculate mg MEX/100 cmZ casing u~ing th~ ~ollowing equation: _ __ ~reca~Ovef)Xor~t~ f~~ o.oo~ X 100~ M~C/100~ 2 3"~

EXAMPLE XIII
It has pre~iously been indica~ed that the tar-depleted liquid smoke composition oP this invention preferahly has a ligh~ transmi~tance of at least 50~ as an indicator tha~ a substantial portion of the tar content has been removed so as to avoid tarring during casing treatment therewith. This preference was demonstrated by a serieC of tests in which ~oyal Smoke AA wa5 contacted under extraction conditions in the previously described manner with methylene chloride solvent in various liquid smoke solution to liquid solvent volume ratios. A
tar-depleted li~uid ~moke fraction was separated and its light tr~nsmittance was measured, also in the previously described manner. The weight percent nonvolatiles (including tars) in this tar-depleted ~ id smoke fraction was also determined. The data from tha~e tests is summarized in Table T ~nd the Figure 13 graph.

_99_ Table T
~ ht Transmittance_vs. Percent Nonvola~iles Liquid Smoke/Solvent % Transmittance % Nonvolatiles As~is liquid smoke 0 8.9 (no solvent) ~, -50/1 3.5 8.5 33/1 8.1 ~0~
~5/1 27.7 8.0 20/1 48.7 6.5 15/1 63.2 5.9 14/1 7~.2 ~.0

10/1 ~2.0 6.0 10/1 76 a 7 5 ~ 9 7/1 7701 5.6 7~
-lo~

Inspection of thi~ data and Fig~re 13 .indicates that light transmittance is heavily influenc~d by the nonvolatiles (including tars) content in the 0 to about 50~ light transmittance range. That is, one must pr~ogressively reduce the -liquid smoke's tar content by, for example, the practice of this invention, to progressively increase the liquid smoke's light transmission from 0 to abou~ 50~. When sufficient tar has been removed to achieve a light transmittance of at least about 50g, a plateau is reached and further improvement in light transmittance does not primarily depend on additional tar removalO
Although preferrea embodiments of this invent.ion have been de~cribed in detail, it is contemplated that modifications thereof may be made and some feature~ may be employed without others, all within the spirit and scope of the invention.
For example it should be understood that as-is tar-containing liquid smokes which are advanta~eously treatable .in the manner o~ this invention may be further concentrated by well known techniques before or a~ter treat~ent, and before use in accordance with this lnvention~ This may be desirable if the prac~i~ioner wishes to apply a highly concentrated form of tar-depleted liquid smoke to a casing wall.
Another contemplated variation from the as-described embodiments of the invention is the method for separating the tar-containing liquid smoke and liquid:601vent mixture into a tar-enriched liquid fraction and a tar-depleted liquid smoke fraction. In the E~amples tbis was done by a single stage extraction with gravity decanting, but other 12896-l 7~

methods may be used as will be understood by those skilled in the art. These methods include single stage contacting and multi-stage con~acting of the two liquids, and such contacting may occur under ambient conditions or under ~levated temperatures and elevated pressures. Such extraction methods may be undertaken in various types of equipment such as liquid-liquid cyclones or centrifugal contac~ors.
Multistage extractions can be undertaken by using a plurality of such devices or by u~ing a vertical countercurren~ column. Countercurrent columns include spray towers, packed columns, deck~d columns containing sieve trays or modified bubble trays, and columns with internal agitation such as rotary disc columns.
The tar-depleted liquid smoke treatment of a tubular food casing surface in the manner of this invention i~ preferably practiced under controlled environmental conditions wherein the presen~e of 20 minute metal par~icles is minimi~edO Thi~ is an important requirement since metal wear particles (primarily iron, copper, brass) in contact ~ith the casing react with the liquid smoke coating, resulti~g in auto-oxidation, discoloration and even 25 cellulose degradation of the treated casing. The discoloration and cellulose degradation occur only in the immediate area of the metal contamination and seldom exceed 2-lO mm diameter in size~ The cellulose degradation may sometimes be severe enough 30 to cause casing breakage during stuffing or processing. The materials of construction of the treatment app~ratus is an important factor in minimizing minute metal particles. These materials should be (l) of high wear resistance, and (2) t~
~102-nonreactive to the liquid smoke. It has been determined that certain metals and alloys are compatible with these stringent requirements. They are: certain aluminum alloys, chrome plating, tin alloys, and certain stainless steels. Care must -also be used .in other steps of casing manufacture and handling to minimize the presence of minute metal particles.

...

1289~-1 7~

Example XIV
Four ~amples of tar-depleted liquid smoke were prepared with varying light transmittance values using the solvent extraction method. ~he as-is liquid smoke solution used was ~Charsol C-12n, ~ and had an absorptive power of a~out 0.5 at a wave length of 340nm, and a p~ of about 2. Each of the three samples were prepared essentially as in Example I, except that each sample was solvent extracted ~o give a differing light ~ransmittance value for each of the resulting tar-depleted li~uid smoke solutions. To an amount of methylene chloride were added about 3785 ml of ~he as-is liquid smoke, and the liquids mixed by stirring or shaking. The methylene chloride containing the tars was separated from ~he liquid smoke by decanting. The light transmittance was varied by varying the amount of methylene chloride used in the extraceion. The light transmittance was measured by dilutihg 1 ml of tar-depleted liquid smoke with 10 ml of water and measuring transmittance relative to water on a Hitachi Model 100-60 spectophotometer at a wave length of SS0 nm. In Tabl~ V are shown the amount, for each sample, o~ meehylene chloride (MeCl) to solvent extract the tars from the as-is smoke, and the p~ and light transmi~ance of the tar-deple~ed liquid smoke product.
Table U
Sample MeCl - Light 30 No. ~ Trans.
1 155 2.2 40.%
2 190 2.2 5 3 315 2.~ 60 4 375 2.2 84.

12896~1 3~'~
~o~ -The above prepared samples were applied to a gel stock ~onfibrous frankfurter casing ~size ~o. 25) using the apparatus and method of .Example IV to give a loading of 15~5 grams per square met2r of liquid 5 -smoke. The casings were dried as in Example IV for ~ 3 minutes at ~ drying temperature between about 80C
and about 120C.
During the applica~ion of the tar-depleted liquid smoke, the casing was observed for tar spots thereon and ~he drying guides a~d the sgeeze rolls of the drying unit were observed for tar buildup.
The resul~s of the observations are su~marized in Table V.
Table V
Light Sample Trans. Observation 1 40.~ Tar deposits formed immediately on casing~ Slight s~icking on squeeze rolls. Tar deposits formed on drying guides.
2 50.% Tar deposits formed on casing after five minute8 0 No sticking on squeeze rolls. Tar deposits formed on drying guides.
3 60.% Tar deposits formed on casin~
after twenty minu~es. No sticking on squeeze rolls~ Tar deposits formed on drying guides.
30 4 84.% No tar deposits on the casing or dryer guides. No sticking on squeeze rolls with extended operating (12 hours~.
' ~ As can be ~een by the above re ults, the 35 problems due to the presence of tar in the tar depleted liquid smoke solution, as reflected by the lower light transmittawe values, become less as 1~896-1 ~3 the tar content is lowered or the light transmittance value is increased. Wi~h tar-depleted liquid smoke with a light transmittance of about 40%
the difficulties caused by the ~ars, in particular the sticking on the squeeze rolls, render the coating process inoperahle and this composition is, therefore, unacceptable. At a light transmit~ance of about 50%, there is still difficulties such as the formation of tar spots on the casing after a period oE running time. However, spot free casings are ma~e during the initial running time which are acceptable from a commercial standpoint. As the light tran~mi~tance rises to about 60%, the period of running time before the tar spots appear on the casing is longer and the coating process becomes, therefore, more practical. At a light transmittance of ahout 84% an extended running time can be accomplished without any problems of spotting and tar-buildup. Tar-depleted liguid smokes having a high transmittance, can be used in a coating process without encountering any problems involving tar-buildup or other related difficulties that lead to the shutting down of the coating process.
The names "Royal Smoke", "Cellosolve", "Charsol", "Tween", and "Apollo Ranger", as used in the foregoing text, are trademarks.

Claims (57)

WHAT IS CLAIMED IS:

1. A method of preparing an aqueous liquid smoke composition comprising: providing a tar-containing aqueous liquid smoke solution having an absorptive power of at least about 0.25 at 340 nm. wave length and an organic liquid solvent which is either nonreactive with said liquid smoke solution or reactive with said liquid smoke solution to form a derivative liquid solvent, with said liquid solvent being immiscible in the liquid smoke solution and having a hydrogen bonding solubility parameter in the liquid smoke environment of at least about 2.7; contacting said liquid smoke solution and said liquid solvent in a volume ratio between about 1:1 and 65:1 of liquid smoke solution to liquid solvent, under extraction conditions to form a tar-enriched liquid solvent fraction and a tar-depleted liquid smoke fraction; and separating the fractions to provide said tar-depleted liquid smoke as said aqueous liquid smoke composition.

2. A method according to claim 1 in which the liquid solvent has a sum total of hydrogen bonding solubility parameter plus weight percent solvent solubility in water of between about 2.7 and 9, and said liquid smoke solution and said liquid solvent are provided in a volume ratio of at least about 6:1 of liquid smoke solution to liquid solvent.

3. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid content of at least about 7 weight %.

4. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid content of between about 7 and about 9 weight % and said solvent is provided in a volume ratio between about 30:1 and about 65:1 of liquid smoke solution to liquid solvent.

5. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid content of between about 9 and about 11.5 weight % and said solvent is provided in a volume ratio between about 15:1 and about 30:1 of liquid smoke solution to liquid solvent.

6. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid content greater than about 11.5 and said solvent is provided in a volume ratio between about 7:1 and about 25:1 of liquid smoke solution to liquid solvent.

7. A method according to claim 4 in which said solvent is a di- or trihalogen substituted methane liquid.

8. A method according to claim 5 in which said solvent is a di- or trihalogen substituted methane liquid. .

9. A method according to claim 6 in which said solvent is a di- or trihalogen substituted methane liquid.

10. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid-content greater than about 11.5, methylene dichloride is said liquid solvent, and said methylene dichloride is provided in a volume ratio between about 7:1 and about 25:1 of liquid smoke solution to methylene dichloride.

11. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid content greater than about 11.5, bromochloromethane is said liquid solvent, and said bromochloromethane is provided in a volume ratio between about 15:1 and about 25:1 of liquid smoke solution to bromochloromethane.

12. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid content greater than about 11.5, chloroform is said liquid solvent, and said chloroform is provided in a volume ratio between about 1:1 and about 16:1 of liquid smoke solution to chloroform.

13. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution has a total acid content greater than about 11.5, bromoform is said liquid solvent, and said bromoform is provided in a volume ratio between about 1:1 and about 3:1 of liquid smoke solution to bromoform.

14. A method according to claim 1 in which a high pH constituent is added to said tar-depleted liquid smoke for at least partial neutralization thereof to form said aqueous liquid smoke composition.

15. A method according to claim 1 in which said tar-containing aqueous liquid smoke solution is at least partially neutralized to a pH of at least about 4, and is contacted with said liquid solvent.

16. A method according to claim 15 in which the temperature of said liquid smoke solution during the at least partial neutralization is controlled so as not to rise above about 40°C.

17. A tar-depleted smoke colored and smoke flavored tubular food casing prepared by the steps of: providing a tar-containing aqueous liquid smoke solution having an absorptive power of at least about 0.25 at 340 nm. wave length and an organic liquid solvent which is either nonreactive with said liquid smoke solution or reactive with said liquid smoke solution to form a derivative liquid solvent, said liquid solvent being immiscible in the liquid smoke environment and having a hydrogen bonding solubility parameter of at least about 2.7;
contacting said liquid smoke solution and said liquid solvent in a volume ratio between about 1:1 and about 65:1 of liquid smoke solution to liquid solvent, under extraction conditions to form a tar-enriched solvent fraction and a tar-depleted liquid smoke fraction; separating the fractions to provide said tar-depleted liquid smoke; and treating a surface of a tubular food casing with said tar-depleted liquid smoke in sufficient quantity to provide a casing wall containing smoke coloring and flavoring constituents and having an absorptive index of at least about 0.2 at 340 nm. wave length.

18. A tar-depleted smoke colored and smoke flavored casing according to claim 17 in which the liquid solvent has a sum total of hydrogen bonding solubility parameter plus weight percent solvent solubility in water of between about 2.7 and about 9, and said liquid smoke solution and said liquid solvent are provided in a volume ratio of at least about 6:1 of liquid smoke solution to liquid solvent.

19. A tar-depleted smoke colored and smoke flavored casing according to claim 17 in which the treated casing wall has about one-half the phenol weight content of an identical casing wall treated in an identical manner by said tar-containing aqueous liquid smoke solution.

20. A tar-depleted smoke colored and smoke flavored casing according to claim 17 wherein only the outer wall of said tubular food casing is treated with said tar-depleted liquid smoke such that the exterior surface of the treated casing is darker than the interior surface of said casing.

21. A tar-depleted smoke colored and smoke flavored casing according to claim 17 in which said tar-containing aqueous liquid smoke solution has a total acid content of at least about 7 weight %.

22. A tar-depleted smoke colored and smoke flavored casing according to claim 17 in which said tar-containing aqueous liquid smoke solution has a total acid content of between about 7 and about 9 weight %.

23. A tar-depleted smoke colored and smoke flavored casing according to claim 17 wherein the initial staining index of said casing is at least about 0.2.

24. A tar-depleted smoke colored and smoke flavored casing according to claim 17 wherein said tar-containing aqueous liquid smoke solution is at least partially neutralized to a pH above about 4, and is then contacted with said liquid solvent.

25. A tar-depleted smoke colored and flavored casing according to claim 24 wherein the temperature of said liquid smoke solution during the at least partial neutralization is controlled so as not to rise above about 40°C.

26. A tar-depleted smoke colored and flavored casing according to claim 17 wherein said tar-containing aqueous liquid smoke solution has a total acid content greater than about 11.5 weight and said liquid solvent is methylene dichloride.

27. A tar-depleted aqueous liquid smoke solution with smoke coloring and smoke flavoring capability, prepared by the steps of: providing a tar-containing liquid smoke solution having an absorptive power of at least about 0.25 at 340 nm.
wave length and an organic liquid solvent which is either nonreactive with said liquid smoke solution or reactive with said liquid smoke solution to form a derivative liquid solvent, said liquid solvent being immiscible in the liquid smoke solution and having a hydrogen bonding solubility parameter in the liquid smoke environment of at least about 2.7;
contacting said liquid smoke solution and said liquid solvent in a volume ratio between about 1:1 and about 65:1 of liquid smoke solution to liquid solvent, under extraction conditions to form a tar-enriched liquid solvent fraction and a tar-depleted aqueous liquid smoke fractions and separating the fractions to provide said tar depleted aqueous liquid smoke fraction as said tar-depleted aqueous liquid smoke solution.

28. A tar-depleted aqueous liquid smoke solution according to claim 27 in which the liquid solvent has a sum total of hydrogen bonding solubility parameter plus weight percent solvent solubility in water of between about 2.7 and about 9, and said liquid smoke solution and said liquid solvent are provided in a volume ratio of at least about 6:1 of liquid smoke solution to liquid solvent.

29. A tar-depleted aqueous liquid smoke solution according to claim 27 in which said contacting and separating are performed so as to provide an aqueous liquid smoke solution with at least 50% light transmittance.

30. A tar-depleted aqueous liquid smoke solution according to claim 27 in which said tar-containing liquid smoke solution has a total acid content of between about 7 and about 9 weight %, and said liquid solvent is provided in a volume ratio between about 30:1 and about 65:1 of liquid smoke solution to liquid solvent.

31. A tar-depleted aqueous liquid smoke solution according to claim 27 in which said tar-containing liquid smoke solution has a total acid content of between about 9 and about 11.5 weight % and said liquid solvent is provided in a volume ratio between about 15:1 and about 30:1 of liquid smoke solution to liquid solvent.

32. A tar-depleted aqueous liquid smoke solution according to claim 27 in which raid tar-containing liquid smoke solution has a total acid content greater than about 11.5 weight % and said liquid solvent is provided in a volume ratio between about 7:1 and about 25:1 of liquid smoke solution to liquid solvent.

33. A tar-depleted aqueous liquid smoke solution according to claim 30 in which said liquid solvent is a di- or trihalogen substituted methane.

34. A tar-depleted aqueous liquid smoke solution according to claim 31 in which said liquid solvent is a di- or trihalogen substituted methane.

35. A tar-depleted aqueous liquid smoke solution according to claim 32 in which said liquid solvent is a di- or trihalogen substituted methane.

36. A tar-depleted aqueous liquid smoke solution according to claim 27 in which said tar-containing liquid smoke solution has a total acid content greater than about 11.5 weight %, methylene dichloride is said liquid solvent, and said methylene dichloride is provided in a volume ratio between about 7:1 and about 2501 of liquid smoke solution to methylene dichloride.

37. A tar-depleted aqueous liquid smoke solution according to claim 27 having an absorptive power of at least 0.15 at 340 nm. wave length.

38. A method for producing a smoke colored and smoke flavored foodstuff comprising the steps of: providing a tar-containing aqueous liquid smoke solution comprising a mixture of smoke coloring and smoke flavoring constituents having an absorptive power of at least about 0.25 at 340 nm. wave length and an organic liquid solvent which is either nonreactive with said liquid smoke solution or reactive with said liquid smoke solution to form a derivative liquid solvent, said liquid solvent being immiscible in the liquid smoke solution and having a hydrogen bonding solubility parameter in the liquid smoke environment of at least about 2.7; contacting said liquid smoke solution and said liquid solvent in a volume ratio between about 1:1 and 65.1 of liquid smoke solution to liquid solvent, under extraction conditions to form a tar-enriched liquid solvent fraction and a tar-depleted liquid smoke fraction; separating the fractions to provide said tar-depleted liquid smoke as an aqueous liquid smoke composition, treating a surface of a tubular food casing with said tar-depleted aqueous liquid smoke composition in sufficient quantity to provide an absorptive index of at least about 0.2 at 340 nm.
wave length for the casing wall; stuffing the so-treated casing with foodstuff and processing the resulting encased foodstuff under conditions sufficient to transfer smoke color and smoke flavor constituents from the casing to the encased foodstuff.

39. A method for producing a smoke colored and smoke flavored food product according to claim 38 in which the liquid solvent has a sum total of hydrogen bonding solubility parameter plus weight percent solvent solubility in water of between about 2.7 and 9, and said liquid smoke solution and said liquid solvent are provided in a volume ratio of at least about 6:1 of liquid smoke solution to liquid solvent

40. A method for producing a smoke colored and smoke flavored foodstuff according to claim 38 in which said tar-containing aqueous liquid smoke solution is at least partially neutralized to a pH
of above about 4, and is contacted with said liquid solvent.

41. A method for producing a smoke colored and smoke flavored foodstuff according to claim 40 in which the temperature of said liquid smoke solution during the at least partial neutralization is controlled so as not to rise above about 40°C.

42. A method for producing a smoke colored and smoke flavored foodstuff according to claim 38 in which said tar-containing aqueous liquid smoke solution has a total acid content of at least about 7 weight %.

43. A method for producing a smoke colored and smoke flavored foodstuff according to claim 38 in which the wall of the treated casing has about one-half the phenol weight content of an identical casing wall treated in an identical manner by said tar-containing aqueous liquid smoke solution.

44. A method of producing a smoke colored and smoke flavored foodstuff according to claim 38 in which said contacting and separating are performed so that said tar-depleted aqueous liquid composition smoke has at least 50% light transmittance.

45. A method for producing a smoke colored and smoke flavored encased foodstuff according to claim 38 in which said tar-containing aqueous liquid smoke solution has a total acid content of between about 7 and about 9 weight % and said liquid solvent is provided in a volume ratio between about 30:1 and about 65:1 of liquid smoke solution to liquid solvent.

46. A method for producing a smoke colored and flavored foodstuff according to claim 38 in which said tar-containing aqueous liquid smoke solution has a total acid content of between about 9 and about 11.5 weight % and said liquid solvent is provided in a volume ratio between about 15:1 and about 30:1 of liquid smoke solution to liquid solvent.

47. A method for producing a smoke colored and smoke flavored foodstuff according to claim 38 in which said tar-containing aqueous liquid smoke solution has a total acid content greater than about 11.5 weight % and said liquid solvent is provided in a volume ratio between about 7:1 and about 25:1 of liquid smoke solution to liquid solvent.

48. A method for producing a smoke colored and smoke flavored encased foodstuff according to claim 45 in which said liquid solvent is a di- or trihalogen substituted methane liquid.

49. A method for producing a smoke colored and smoke flavored encased foodstuff according to claim 46 in which said liquid solvent is a di- or trihalogen substituted methane liquid.

50. A method for producing a smoke colored and smoke flavored encased foodstuff according to claim 47 in which said liquid solvent is a di- or trihalogen substituted methane liquid.

51. A method for producing a smoke colored and smoke flavored foodstuff according to claim 38 in which said tar-containing aqueous liquid smoke solution has a total acid content greater than about 11.5 weight %, methylene dichloride is said liquid solvent, and said methylene dichloride is provided in a volume ratio between about 7:1 and about 25:1 of liquid smoke solution to methylene dichloride.

52. A tar-depleted smoke colored and smoke flavored casing according to claim 17 in which said casing comprises non-fibrous cellulosic casing.

53. A tar-depleted smoke colored and smoke flavored casing according to claim 17 in which said casing comprises fibrous cellulosic casing.

54. A tar-depleted smoke colored and smoke flavored casing according to claim 17 in which said absorptive index is at least about 0.4.

55. A method for producing a smoke colored and smoke flavored foodstuff according to claim 38 in which said smoke treated casing has an absorptive index of at least about 0.4.

56. A method according to claim 1 wherein the organic liquid solvent is acetophenone.

57. A method according to claim 1 wherein the organic liquid solvent is n-octyl alcohol.