CA1227690A - Tar-depleted liquid smoke solutions and methods - Google Patents

Abstract

TAR-DEPLETED LIQUID SMOKE SOLUTIONS
AND METHOD
ABSTRACT
Tar-depleted liquid smoke solutions are made by generating a smoke vapor, selectively solvent extracting the tars from the smoke vapor, and absorbing the color, flavor and odor constituents of the smoke vapors into an aqueous medium. The aqueous tar-depleted liquid smoke has a high coloring ability, a high concentration of carbonyls, and a low phenol content.

Description

'769(~

TAR-DRPLET~D LIQUID STOKE SOLUTIONS
AND Method FIELD OF THE INVENTION
This invention relate to: (a) a method for preparing tar-depleted liquid smoke solution from smote vapors, by tar-depleted liquid smoke compositions, (c) tar-depleted, partially neutralized liquid smoke compositions, (do food casings colored and flavored with tar-depleted liquid smoke compassion, (e) a method for making ford casing colored and flavored with tar-deple~ed liquid smoke composition, and (f) a method for preparing a smote colored and flavored foodstuff encased in a cawing.
BACKGROUND OF THE INVENTION
tubular cellulosic food casings are used extensively for processing a great variety of meat product and other food items. The food casings are generally tunneled cubing of various diameter prepared from reconstituted arterial such as regenerated cellulose. Cellulosic food casings may also be prepared with fibrous webs embedded in the wall thereof, such casings commonly being referred to a "fibrous food Congo."
The many different recipes and modes of processing that are used by the prosody food industry to suit different tastes, and even regional preferences, generally necessitate the use of food casings with a variety of characteristics. In Rome instance, for example, food casings are required to have multi functional use wherein they serve a : ' - ~227~

~ontainer6 during the processing of a food product encased therein, and when Allah verve a a protective wrapping for the finished product. It the processed meat industry, however, the food Congo used it the Reparation of many ye of meat products, such as Yore types of assuage, such a fran~furter6, bolognas and the like, beef rolls, hams and the like, are frequently removed from about the prosody meat product prior to slicing and/or final packaging.
Surface appearance and flavor are important factor in the commercial and consumer acceptance of processed meat products, and a common feature of ~06t varieties of such product involves the use of "smoking" for imparting oharacteri~tic flavor and color thereto. The "smoking" of food product is generally accomplished by the food processor subjecting the food product to actual contact wit smoke in a gaseous or cloud-like form. Such "smoking" prowesses, however, have not been considered completely satisfactory for a variety of reason, including the inefficiencies and lacy of uniformity of the smoking" operation. Because of the 6hortcoming6 experienced, many meat packer now employ various type of liquid aqueous 601utions of wood-derived Moe constituents, commonly called "liquid smoke ~olution6" what have been developed and used commercially in the food processing industry for the processing of many type of meat and other food product. For convenience in this specification, these commercially available "liquid smoke" 601ution6 in their as-purcha6ed Tao will be ~L22'7~

frequently referred to herein a "aye" liquid smote.
Example of prows for preparing as-is liquid smoke are described in United States Patent 3,106,~73, issued October 8, 1963 to Hollenbeck, and United States Patent 3,873,741, issued March 25, 1975 Jo Melter et at. The processes for making liquid smote can be generally de~cribad as comprising heating wood in an oxygen-controlled atmosphere Jo effect the thermal decomposition of wood and to generate smoke, and I contacting the smoke with an aqueous solution to condense and to recover the coloring and flavoring constituents of the smoke. The condensed as-i& liquid smoke 601utions generally also contain various tarry-sub6tance6, a well a organic acids such as acetic acid.
The application of "liquid smoke solutions"
to meat product it generally carried out in a variety of way, including spraying or dipping an encased food product during the processing thereof, or by incorporating toe "liquid smoke solution" in the recipe itself. 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 solution" in the meat recipe doe not always provide the desired surface appearance because of dilution of smoke ingredients. Incorporation in the recipe also reduce the stability of the meat elan, and will adversely affect taste if high concentrations are used. Application of liquid ~L22'7691) smoke to encased food product by the Good processor, such as by spraying or dipping, also causes unwanted pollution and equipment corrosion problem for the food processor. In addition, encased sausages treated by application of the liquid smoke during commercial processing have been found to yield, after peeling the cawing from the treated encased food product, sausages which are lacking in smoke color uniformity between individual sausage and batches of siege. Even more undesirable is the lack of uniformity of coloration which often appear on the surface of the individual sausage, including light and dark streaks, light and dark blotches, and even uncolored spots which especially appear at the ends of sausages.
Several methods are known for coating either the interior or the exterior of a food cawing with various liquid substance designed to meet particular processing requirements, as, for example, substances that affect the adhesion properties of the cawing. Some of the copings known in the art contain a liquid smoke a a con~tituer.t thereof.
Known methods for coating an as-is type liquid smoke solution internally in a cawing haze been found to be costly and also to limit the speed of a continuous high speed production line.
Renown method for coating the external surface of a casing, particularly a cellulosic gel-6tock cawing, wit assay type liquid smoke solution, result in problems due to the tar context of these smoke solutions. That is, during the coating process, tarry deposits accumulate on the ~2~7~9~

carrier rolls and the squeeze roll of the treatment unit which eventually forces shutdown of the treatment swept.
One solution to the above-mentioned problems of imparting smote color and flavor to a foodstuff is to use "tar-depleted" liquid smoke solutions to coax the interior or preferably tube exterior surface of the cawing. However, until recently, tar-depleted liquid move solutions were unavailable, and methods for making the tame were unknown. As indicated above, it has been found thaw when a cellulosic food casing, made from a fibrous or non-fibrous gel stock, is treated with a highly acidic pi of about 2.0 eon 2.5) tar-containing, aqueous liquid smoke, tarry deposits accumulate on the carrier roll and the squeeze rolls of the smoke treatment unit, keg the cawing to stick to the rolls and eventually forcing shutdown of eke unit.
The acidity of the liquid smoke also may interfere with peelabili~y of the casing by interfering with the action of the peeling aid used, finch as, for example carboxymethyl cellulose. Aqueous liquid stoke solution are generally very acid, having a pi of 2.5 or less and a titratable acidity of at least 3 weight percent.
It was found that tar could be removed from the liquid smoke by neutralizing the aye liquid Moe under controlled temperature conditions to precipitate the tar, and the use of this neutralized, tar-depleted liquid smoke to treat a gel stock cawing would eliminate the problem of tarry deposit. This process I disclosed and 69~

clad in Uni~ea Sue Pant ~pplicDtion serial aurora ~17,î~2. filed I Satyr 19~. my I En.
N~chol~o~ . .
Caesar kiwi to rules Boyle he art O
gibe tar-~epletea liquid smoke till osseous siqni~ica~t eye ~:olorillg capability. It bay been generally believe that ye jars on a liquid ~rQolce vainly contribute to gee coloring ability of the liquid smoke. Err, ye aye recently been found that tbi~ I jot toe cave, blot Swat otter ~on~titu~nt~ of the l~gui~ Melissa, Ballard is be vainly Abe eaE~onyl~, Howe a Gore 6ignif inn role I the coloring ability ox toe liquid Sue.
Another trod using "solvent tractor prows cay be applied to Elk *ar-~pleted l~guid emote. For example. such a prows it clue sod clue in Utah State Relent Number 4,431,033 issued by 14, 1984 to I. D. ~iehol~on. hi pry kippers (a contacting ~ar-eonta~ning guy owe solution baying on abortive power ox it Lowe tout 0. 25 at a Dave Lyon of byway 3~0 no, Thea either nonreact~e or reactive organic lug solvent which bd6 a hydrogen bonding volubility parquetry of at Lotte about 2.7, an vacua 16 ~mi~c~ble ED toe qu~ous Lou kiwi solution under ~onaitions fount Jo form a ~ar-enric~ed solvent fraction end tar-d~pletea lug smoke rocket, an (b) separating toe Lowe joke traction to o'er a tar-depleeea liquid zoo. Using BUCK solvent xtr~ction method. it it pueblo to Ike tar-d~pl~t~a ~lqui~ Mohawk solution ho g a /, . .

~ZZ'76~

high capability to impart smoke color odor, and flavor, without requiring neutralization of the tar-containing liquid smoke.
The tar-depleted liquid smoke made from the solvent extraction process, unless it it neutralized, it generally highly acidic, which may also interfere with the action of the pee lability agent, such as certain water soluble cellulose ether, which may be used on the casing. To alleviate this problem, the tar-depleted liquid smoke may be partially neutralized. However, since the coloration ability of the liquid stoke declines with increasing phi the tar-depleted liquid smoke is only "partially neutralized" Jo a degree such that the peel~bility agent is not significantly affected and the coloration ability of the smoke is retained. the term "partially neutralized", a used herein, is intended to refer to liquid smoke compositions having a pi greater than about 3.
preferably having a pi within the range of from about 3 to about 6.5, and even snore preferably having a pi within the range of from about 3 to 5.
By providing a partially neutralized, tar-depleted liquid smoke made from a solvent extraction process, the problems due to acidity are avoided to a large extent while a significant degree of the coloring ability of thy original assay liquid smote is retained.
The above described liquid smoke compositions, whether aye or tar-depleted, have been found suitable for use with fibrous cellulosic food casing. When used with non fibrous casings, ~LZ2769~

however, it aye been one chat eye liquid smoke solutions, in Tory uneo~central:e~ ~6-~a~ufactured o'er part a Luke color, Odor an flavor to eye ooastuf I, us owe on I quantity us iciest Jo be acceptable for all eo~mercial application. Because noaf~brous Cannes art thinner elan ~ibrou6 clunks.
tube liquid ~sDolce cannot lye on a practical manner "coated on, plywood to, or incorporated on toe casing Jo an extent sufficient Jo always impart toe d~sirea joke color, odor and flavor so a foods~uf~. Shea composition, therefore, cantos be universally u6~d, King restrict vainly for use web f~brou6 counsel.
It order to prove lug smoke owlish having coloring Bills us iciently high to be use on aon-fi~rous Congo. tar-depletea liquid -stoke solution hove teen conceDltr~ed to form tar-~epleted concener~t~a liquid stoke Utahan, for example. a closed in United State Patent Number 4,540,613 issued Stemmer in, 14~
to M. D. Nicbo loon end J . H .
BeckrDan. Tile triplet, concentrated liquid eye solution Dave a Niger coloring ability.
~berefore, it it possible wren using casings costed with replicated, concentrated, liquid owe oiliness, Jo have su~ici~nt coloring ability to - color lottery photo, oven whey u6~ng a nonfibrou~ casing.
Tar-depl~t~a, e~ncentrated lieu a smoke ~olutlon6 eta be aye by a process Waco Cooper roving on unneutr~lized, tar-depleted liquid owe- composition jade Roy a solvent extraction ,J3L~ I

prows, and concentrating the unreleased tar-depleted liquid smoke. The concentrated, tar-depleted liquid smoke product ha ~urpri6ing and advantageous physical properties, and it Jay be optionally neutralized to provide a partially neutralized, concentrated, tar-depleted liquid kiwi composition.
The tar-depleted, concentrated liquid kiwi solutions, described above, avoid the difficulties inherent Zen an assay smoke is concentrated, wherein there is an increased concentration of undesirable chemical substance. for example tar, and certain o'er constituents which are Doria, or example phony, which contribute to the luring ability, but cause an undesirably Strong or "caustic" flavor in sigh concantration6.
One problem in ~oncentrati~q liquid smoke solutions is that when a neutralized liquid smoke it concentrated to a suitably high degree for coating on non fibrous casings, there it a significant and undesirable increase in viscosity, rendering toe ruling concentrated, liquid smote unsuitable for commercial use. The increase it viscosity of neutralized, a and tar-depleted liquid smoke solution which are concentrated is in large part due to the presence of acids, mostly acetic acid, in the liquid Sue. Upon neutralization of the acids in toe liquid owe, salts of Neutralization of these Audi are formed, and it is these salt that are the substances which mainly contribute to the high visc06ity. In non-concentrated smoke solution which are neutralized, the concentration of these I

~lt6 us snarl not hug tough to cause a ~iffi~ulty. o'er, when ~eutral~2ea kiwi us counterweighted the ¢oncen~rat~on of eye ~lt6 increases ~ropor~io~ally iota ye ~eqree of ~one2ntration, resulting in exile concentration of those alto no thus, on undesirably it viscosity.
It aye now been found by Nicholson and Beckman as disallowed in the above-cited United States 4,540,613 : I, that wren concentrating on unneutralized, tar-depletea, Lydia kiwi, the acid content it not proportionally increased Vito the degree of concentration of the liquid smoke. That it, as the unneutralized, tar-depleted smoke is concentrated, the acid awing the viscosity difficulties are apparently Yellowtail to a significant degree. Thus, it it possible to wake concentrated liquid Moe solutions, voile retaining a usably low viscosity. The ~ar-deplete~ conoentr3tea liquid Moe ~oapo~itions ox toe above iota Serial No.
4~5,924~ eke ox their lo total acid content, haze a low ~i~co~ity when neutralized.
Additionally, thy are Allah tar-depletea, and throb pry the processing advantages heretofore fount only iota the ye of unconcentrated, t~r-~epl~t~d liquid joke ~olut~on6. They also Dave substantially increased owe coloring and flavoring a ties over unconcentra~ed, tar-depleted liquid Dow solution There it alto an increase in the viscosity I concan~ratea it smoke Solon. which Jay be ~l2276~C~

due in par to the presence of the high molecular weight polymeric tar constituents in the liquid smoke composition. The low amount of tars in the tar-deple~ed concentrated liquid smoke composition also contribute Jo the low viscosity of both the unneutralized and partially neutralized forms.
The tar-depleted concentrated liquid smoke solutions have many advantages. However, heretofore they required additional processing of as-is liquid smoke. The extra processing includes the treatment to tar-deplete the as-is smoke and the processing to concentrate the resulting tar-depleted liquid smoke, when a concentrated liquid smoke is desired. This extra processing of the as-is liquid smote to prepare the concentrated and unconcentrated, tar-depl~e~ed liquid smoke solutions requires expensive processing equipment and extra labor costs. It would be an advantage, therefore, to produce tar-depleted liquid smoke solutions, having the coloring ability of either concentrated or unconcentrated liquid smote solutions, without extra process Taipei beyond the condensation of the smoke vapors to form a liquid smoke solution.
In United States Patent 4,359,481, issued November 16, 1982 to Suits et at., is disclosed a process for making a liquid smoke having reduced tar-content by fractional condensation, i.e. by cooling the smoke vapors in various stages. The liquid smoke product of the Suits et at. it produced for its flavoring ability, and is not shown to have a high coloring ability.

I 2~12 -An object of an aspect of the invention is, therefore 3 to produce tar-depleted liquid smoke solutions without the extra processing of as-is liquid smoke.
An object of an aspect of the invention is to provide a method for preparing tar-depleted liquid smoke solutions, characterized by fewer process steps and less expensive equipment than heretofore possible.
An object of an aspect of the invention is to provide a method to produce, from the condemn-station of smoke vapors, tar-depleted liquid smoke solutions having degrees of coloring ability, equivalent to unconcentrated liquid smoke solutions.
An object of an aspect of the invention is to provide a method to produce, from the condensation of smoke-vapors, tar-depleted liquid smoke solutions having degrees of coloring ability, equivalent to concentrated liquid smoke solutions.
An object of an aspect of the invention is to produce tar-depleted liquid smoke solutions having a high content of carbonless.
An object of an aspect of the invention is to produce tar-depleted liquid smoke solutions having a high coloring ability.
An object of an aspect of the invention is to produce a concentrated tar-depleted liquid smoke with high coloring ability and low viscosity.
Other objects will become apparent in the description that follows.
SUMMARY OF THE INVENTION
An aspect of the present invention is a method for preparing a tar-depleted liquid smoke solution which comprises (1) thermally decomposing ~L2;2~9~ .

wood in an oxygen-controlled atmosphere to generate smoke vapors, (2) selectively vent extracting the awry from the generated smoke vapors, and (3) absorbing the smoke vapors into an aqueous medium to provide a tar-depleted liquid smoke solution.
Another aspect of the present invention is a method for preparing a tar-depleted liquid smoke 601ution which comprises (1) thermally decomposing wood in an oxygen-oontrolled atmosphere to generate smoke vapors, (2) contacting the smoke vapors, water and an organic solvent having volubility parameter greater than about 2.7, to form a tar-containing liquid solvent phase and an aqueous liquid smote phase, I separating the liquid smoke phase from the the liquid solvent phase to provide a tar-depleted liquid smoke 601ution.
Another aspect of the prevent invention is an improvement in a method for preparing a tar-depleted liquid smote 601ution which comprises thermally decomposing wood in an oxygen-controlled atmosphere to generate smoke vapors and condensing the smoke vapors into an aqueous medium, the improvement of selectively removing the tars from the smoke vapor, by a process which comprises contacting the smoke vapors with an organic solvent having a volubility parameter greater than about 2.7.
Another aspect of the present invention is any of the above methods wherein the smoke vapors are contacted with water and a solvent in a single contacting zone.
Another aspect of the present invention is any of the above methods wherein the smoke vapor ~L22q~

are contacted with a solvent in a first contacting zone and thereafter contacted with water in a second contacting zone.
Another aspect of this invention is a tar-depleted liquid smoke composition prepared by a method which comprises (1) thermally decomposing wood in an oxygen-controlled atmosphere to generate smoke-vapors, (2) selectively solvent extracting the tars from the generated smoke vapors, and (3) absorbing the smoke vapors into an aqueous medium to provide a tar-depleted liquid smoke solution.
Another aspect of this invention includes a process for preparing a tar-depleted, partially neutralized liquid smoke solution which comprises preparing a tar-depleted liquid smoke by any of the above defined methods and thereafter partially neutralizing the tar-depleted liquid smoke to a pi greater than about 3. preferably to a pi between about 3 and about 6.5, and most preferably to a pi between about 3 and about 5.
Another aspect of this invention includes either an unneutralized or a partially neutralized tar-depleted liquid smoke composition made from any of the above processes.
Another aspect of this invention includes a tar-depleted smoke colored and smoke flavored tubular food casing which is made by contacting a tubular casing wall with any of the above described liquid smoke solutions.
Another aspect of this invention includes a method for making a tar-depleted smoke colored and smoke flavored tubular food casing by applying any of the above described liquid smoke solutions to a tubular casing.

~27~
- aye -Another aspect of this invention includes a method for preparing a smoke colored and smoke flavored foodstuff which comprises stuffing the above defined tubular casing with a foodstuff and processing the resulting encased foodstuff under f-~3 Jo I

condition sufficient to transfer smoke color and smoke flavor constant to thy encased foodstuff.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 it a flow diagram of a continuous process for making a ~ar-depleted liquid smoke according to the invention.
Figure 2 is a schematic view of a laboratory apparatus for making a tar-depleted liquid smoke according eon the invention.
Figure 3 it a schematic view of an apparatus suitable for treatment of the external surface of a food cawing with the liquid smote composition manufactured by the method of this invention.
Figure 4 is a 6chsmatic view of an apparatus similar to and performing the save functions as the apparatus of Figure 3, but with a chamber fox partially drying the kink treated with the liquid smoke composition of this invention to a desired moisture content while in an inflated condition.
Figure 5 is a schematic view of an apparatus similar to and performing the tame function a the apparatus of Figure I, but with mean for partially drying of the casing treated with the liquid smoke composition manufactured by the method of this invention while in a flat condition.
Figure 6 is a schematic view of tube apparatus used in Example 5 for making tar-depleted liquid smoke.

- -7~igC~

DESCRIPTION OX THE INVENTION
As used in this specification and the appended claims, the following terms are defined as follows:

"Solution" is meant to encompass homogeneous true solutions, as well as emulsions, colloidal suspensions, and the live.

"Smoke color, odor, and flavor constituents", refers to the smoke color odor and flavor constituents present in natural liquid smoke solutions manufactured by the condensation of smoke vapors generated by the partial combustion of hardwoods. Examples include liquid smoke solutions in their as-is or present commercially available Norm.

abrupt power" is a measure of the coloring capability of the liquid move solution. Absorptive power is measured by placing 10 my of a liquid smoke solution Jo be tested (either tar-containing liquid smoke or tar-depleted liquid smote) in a disposable vial, and 5 milliliters of methanol is added thereto. The two components are mixed by inverting the vial, and the ultraviolet absorption value of the mixture is then measured at a wavelength of 340 no. It should be noted what whereas 3Lz~7i69~

tar-content it a significant contributor to thy absorptive power measurement, tar only contributes to the staining of food in a minor way if at all. Thus, in commercially available assay smoke solutions, absorptive power includes a measurement of tar-content and the coloring constituents such as carbonless, phenols and acids. This means that absorptive power of a smoke solutions and tar-depleted smoke solutions may be used to rank them by smoke coloring ability. However, absorptive power of as-is liquid smoke cannot be numerically compared with the absorptive power of tar-depleted smoke solutions used in this invention because of the absorptive effect of tars.

"Absorptive index" is a measure of the coloring ability of a easing treated with the liquid smoke solution of the invention. It is measured by cutting out 2 square inches (12.9 square centimeters) of toe casing to be tested and placing the cut-out portion in 10 milliliters of methanol. After about 1 hour of soaking tire, the methanol has extracted all of the smoke components out of the casing, and the ultraviolet absorption value of the resulting smoke component-containing methanol is determined at a wave length of 340 no.

~2~7~90 .

"Total acid content" refer to the concentration of acid, principally acetic acid, that are present in the liquid smoke. Total acid content it measured by the following procedure:

1. Leigh accurately 1 milliliter of liquid smoke (filtered if necessary) in a 250 milliliter beaker,

2. Dilute with 100 milliliter of distilled water and titrate with standard Own Noah to a pi of 8.15 (as measured on a pi meter),

3. Calculate the total acid content a weight percent of acetic acid (Ha), using the following conversion;
-1 I 0.1000 N Noah = 6.0 my Ha This method can be used to measure total acid convent of tar-containing liquid smoke 601utions and tar-depleted liquid smoke solutions that have not been neutralized.

"Light transmittance" is measured for mixtures of liquid smoke solution and water. This measured light transmittance trelati~e topper water) is inversely related to tar-content of the tested liquid smoke, i.e. a high tar-content result in a cloudy liquid withal light tran6mit~ance.
The procedure for measuring light . .
. , . _ .. . .

27~

transmittance is to thoroughly mix a 1 milliliter Alcott of the liquid smoke with 10 milliliter of water, and determine it turbidity-tran~mittance on a 6pectrophoto-Peter u6i~g a light wavelength of 590 no.
The higher the percent transmittance reading, the lower the residual tar concentration in the liquid smoke company.

"Smoke Vapor" refer to the principally gaseous product of the limited combustion of wood. It comprises a complex mixture of wood combustion products and varies according to tube wood used and the burning condition. Chile the smoke vapor is principally Gus, it alto comprises a colloidal suspension of various liquid and solid material.

The smoke vapor in the process of ye invention it generated by the incomplete combustion of wood by limiting or controlling the amount of atmospheric oxygen available or combustion. The smoke vapor may be produced by any suitable method known in the art. Suitable methods include the use of externally heated retort provided with openings for the controlled introduction of air, packing house type kiwi generator, and indirect-heat calciner6, which are essentially cylindrical retorts rotating within a cylindrical furnace. Suitable ~ethod6 of generation of smoke vapor are disclosed I

on the above-cited U. S. 3,106,473 and U. S.
3,873,741.
By practice of the invention, the tars, which are mainly polycyclic aromatic hydrocarbons, are selectively removed from the generated smoke vapors by a method that selectively remove the tars from eke vapor using a solvent that does not remove the smoke color and flavor constituents. Suitable methods for extracting the tars from the smoke vapor include methods of contacting a gas and a liquid, wherein the tars are removed through gas-liquid absorption, Andre liquid-liquid extraction.
The solvent extraction ox the tar from the smoke vapor may be achieved by contacting the smoke vapor with an absorptive liquid, under conditions wherein the tars are selectively removed from the smoke vapor and absorbed into the absorptive liquid. This can be accomplished by using known methods and apparatus used to contact a liquid with a gas phase. Suitable apparatus include plate columns, having cross flow plates, such as sieve plates, bubble-cap and valve plates, and counter flow plates such as doleful plates, turbo grid tray and ripple trays. Also suitable are packed columns waving any of the known packings, such as for examples ra~chig rings, tossing rings, bent saddle, intalox waddles, tolerates, and pall rings. Liquid dispersed contractors such as spray columns, baffle-plate or shower deck columns, and gas-in-liquid dispersed contractors suck as bubblers, sparkers, big speed agitators, rotary disc column, aerators, and the like, are also ~2Z~76~3 suitable, A general description of various method suitable for use in the invention for contacting a gas with a liquid it found in Chemical Engineers handbook, Perry & Hilton, Fifty Edition, page 18-3 to 18-93.
The organic liquid solvent used in the invention should ye immiscible in water and have a hydrogen bonding volubility parameter in the environment of the lockjaw contacting zone of least about 2.7. The organic liquid ennui may be either nonreactive with the smoke vapor or reactive with the smoke vapor to form a derivative organic liquid yenta. If reactive, the derivative solvent should alto have the tame solvent properties as described above.
The hydrogen bonding volubility parameter, as used herein. can be calculated from known literature or experimental vapor pressure data such as the heat of vaporization at 25C. The total volubility parameter IT) may be determined by using the relation of Equation I

To 1 1/2 (1) T l where: aye = Heat of vaporization at 25C.
= Gas constant, T = Temperature in degrees absolute, d Density at 25C, and M - Molecular weight.

:~L2;~7~0 The total syllable parameter value can be separated into its hydrogen bonding Ho or polar (up), and nonpolar (Sup) concatenate. The following relationships are useful for determining the hydrogen bonding parameter value (OH).
Tub M
toga= 3.39066 T 0.15848 - log d I

H= IT (3) where: a = Aggregation number, Tub Boiling point in degrees absolute, To s Critical temperature in degrees absolute.
The theoretical basis for use of volubility characteristics is discussed in the literature.
Tabulations of parameter have been published in Lithe Three Dimensional volubility Parameter and Solvent Diffusion Coefficient," Danish Technical Press, 1967, Copenhagen, by C. M. Hansen. A list of volubility parameters can be obtained from K. L.
Hoyt "Tables o Sealability Parameters", Union Carbide Corporation, 1975, obtainable from Union Carbide Corporation, River toad, Bound Brook, New Jersey 08805.
Suitable organic solvents include halogen dip or tri~ubstituted methanes, such as ethylene dichlorides bromochloromethane, and the like;

~L22769~1 _ 23 -chloroform, bromoform, and the like; acetophenone;
and alcohol liquids such as 2-ethylhexanol, the phenol ether of ethylene glycol, the monohexyl ether of ethylene glycol, n-octyl alcohol, n-~lexyl alcohol, and n-butyl alcohol. The preferred solvent is methylPne dichlorides ~dichloromethane).
The resulting tar-depleted smiles vapors containing smoke flavor, odor, and color constituents can be recovered, by known methods, into an aqueous medium to form an aqueous, tar-depleted smoke solution. These include those described in the above-cited U. S. 3,106,473 and U.
S. 3,873,741. Also included is the use of the gas-liquid contacting equipment listed above.
In a preferred practice of the invention the smoke vapor is contacted with water and a solvent in a single contacting means, that is the color, flavor, and odor constituents are recovered in an aqueous medium in the same contacting means as that used for the contacting of the smoke vapor with the solidity to extract the tar components. This is accomplished by simultaneously introducing water and the organic solvent into the gas-liquid absorption jeans. The resulting product of the process are a waste gas stream, containing some acetic acid that was in the generated smoke vapor and a two phase liquid product. In the two phase liquid product, the kiwi phase contains eke the smoke flavor, color and odor constituents, and is the tar-depleted liquid smoke of this invention. The organic solvent phase contains the tars that were in the generated smoke vapor. Chile a single contacting means is . . ._ _ _ . . . _ . .

~2~76~[) preferred, separate vessel Gould be used for contacting the solvent and the water with the smoke vapor.
Toe condition of the sas-liquid contacting are such thaw color, flavor and odor constituents are tran6fsrred to the aqueous phase to form a liquid smoke solution having sufficient coloring and flavoring ability. In a continuous process, as illustrated by Figure 1, the flow rates of the smoke, waxer and solvent are regulated Jo that the concentration ox the smoke color, odor, and if avow constituent in the aqueous liquid smoke phase is high enough to provide the desired coloring and flavoring ability. It a batch process, such as illustrated by Figure 2 and Example 1, the prows it continued until the concentration of the color, odor and flavor con~titueD~s it high enough to provide the desired flavoring and coloring ability.
In calculating the amount of water introduced it should be considered that water it sly introduced as a gas in the smoke vapor. During the absorption process this water will condense. Although it is preferred to introduce additional water separately, it it possible, due to this water in the smoke vapor, to wake a tar-depleted liquid McKee of the invention with minimal addition of waxer, relying on the water condensed from the smoke vapor to form the bulk of the aqueous phase to absorb the color, flavor and odor constituent.
By Jo regulating the condition, a described above, it is eyeball to make a tar-depleted liquid smoke having the desired concentration of color, flavor, and odor constituent. Previously, tar-depleted liquid smoke 601utions were made from the commercially available as-is liquid smoke solutions, which have only limited concentrations of color, flavor and odor constituent. None of Thea commercially available assay liquid Moe solutions have concentrations high enough Jo coat a casing in one application, such that the casing will sufficiently color and flavor certain food products, such a light colored meats. Commercial liquid smoke 601utions have limited concentrations due to problems involving undesirably high concentrations of tars and phenols whey assay smokes are made in a concentrated form.
Since tar depleted liquid smoke solutions have been made from the low concentration, assay liquid smoke solutions, such solutions also have inadequate flavoring and coloring ability for some applications, and it it necessary to subject these tar-depleted liquid smoke solution to a further concentration process to obtain the desired coloring and flaYori~g ability. By practice of the invention, it is possible to obtain tar-depleted liquid smoke 601ution6 having coloring and flavoring ability equivalent to either concentrated or nonconcen~rated assay derived liquid smoke solutions without further processing.
The aqueous tar-depleted liquid smoke phase, and the tar-containing organic solvent phase, are separated by known methods. These methods include gravity decanting, liquid cycloning, and centrifugal decanting, as well a the use of various ~LZ~:7Çi~

type of separation systems used in solvent erection methods.
A preferred method of the invention for making tar-depleted liquid smoke solution it illustrated by Figure 1. In Figure 1, smoke vapors are generated in a suitable smoke generator 51, The generated smoke vapor it conveyed along line 52 to a counter-current ga~-liquid absorption column 53, such as, for example a packed column, plate column or a spray column. An organic solvent and water are introduced into the top of the column through lines 54 and 55, respectively. In the absorption column 53, the tar are absorbed into the organic solvent, and the color, Flavor and odor con~tituentfi are absorbed into the water, Jo form a two phase liquid product leaving the column through line 56. The remaining unabsorbed gaseous constituent of the smoke vapor leave the column through line 57 a a waste stream. The two phase liquid product compare an aqueoufi, tar-depleted liquid Moe phase 58, and a tar-containing liquid solvent phase 59, which are separated in any known separation apparatus, such as a gravity settling tank 60, into the tar-depleted liquid smoke of the invention which leave through line 62, and the tar-containing solvent which leave through line 61.
The tar-depleted liquid smoke of the invention may be further concentrated. The tar-depleted, liquid smoke of the invention may be concentrated preferably under vacuum condition, a a temperature of lest than about 70C, preferably lets than about 50C. Other suitable concentration 769~

etude are ~iselosed toe abo~e-c~tea United to Patent Number 4,540,613, i~cluai~q frieze dry, spray drying or various other evaporation technique us a YapOr~at~On by owe temperature evaporate lo Baudot environment, or the use of ~orced-~ircula~ion aperture, long be vertical evaporator end agitated evaporator Tube ~ar-depletea joke solution jade by the etude of ye ~nveneion I optionally partially ~eutral~2@a to on extent us that ye pi it wrier Allah about 3. preferably between about 3 and about 6 . I, an core preferably between bout 3 and about 5. The temperature it preferably controlled Uruguay the partial neutralization us thaw toe temperature of tube llquia eye doe not rite above about OKAY, Gore preferably sue Tao it woes not rise above about 30~C.
The partial neutralization of the unneutralized, ~ar-deplated. liquid stoke of the invention Jay be accompli~hea by mixing either a igloo ~lgaline solid with toe tar-aepleted liquid evoke, or example Cole carbonate. sodium bicarbonate, pota~ium bicarbonate. calcium hydroxide, Dow carbonate, oddly, end dummy hydroxide elite or kiwi, or by mixing the liquid joke iota h pi liquid us a kiwi sodium hydroxide sol~tio~. Although toe carbonate a the bicarbonate produce violent owing high Jay KIWI operational di~ficultia6. toe neutralization faction no She acids on the liquid stoke wit bicarbonate I Newark, awoke yo-yo irate ye f ~:~

need for temperature control during the neutralization.
The rate of addition of the neutralizing material to the tar-depleeed liquid smoke depends on the cooling gape fly of the mixing container as well as toe efficiency of the mixing means, a will be understood by those skilled in the art. The coloring ability of the tar-depleted, partially neutralized liquid smoke is not substantially affected by temperature variations during the at 1 exact partial neutralization step, as long as the temperature of the bull liquid is maintained below about 40C, and preferably below about 30C.
The mixing container used for the partial neutralization should be cooled by indirect meanfi, as for example, brine circulating through immersed coil in a closed-circuit refrigeration system. The reason for indirect rather than direct contact between the refrigerant and the tar-depleted liquid smoke is to avoid contamination of the latter.
Another pueblo method for at least partially neutralizing the tar-depleted liquid smoke is by contacting the latter with an ion-exchange material.
The method of the invention for making tar-depleted liquid smoke solution has many advantage over the prior art beyond that of reduced c06ts. As described previously, by this invention tar-depleted liquid smoke solution can be made to have any desired concentration of flavor, color, and odor constituents without undesirable concentrations ox tars and phenols. Typically, the concentration ~.2~27!6,~90 of the colts ~nsti~uent~ corre6pon~ to from about 1 Jo bout yes the cc~centrat~on ox the Lowe it a tar-dlepl~ quid smoke Elude by eke above ~i~6cribed lent traction prows Russell an isles liquid eke hiving about a 12~ aye onto for @xa~pl~ rl3o~ valuable prom Eyed Arrow Pockets Cowan nitowcc, Wisconsin. an advantage of tube invention is that the tar depleted l~quia smiles Solon aye by if e proves of the invention a toggle ~olorlng anility and high carbonyl entreat rethought a correspondingly high content ox ph~!nol6. Typically. tube content ox the phenols is lets kiwi about 10 parent preferably not greater ton 2 pureness, of tube content of the ~arbonyl6. toll 1.5 percent being achievable. The phenol ye bevy to be ye 6ub6tances eye in hug ~e~trat~o~s contribute vainly to the strong or Roy flavor of some ~oneentrated liquid owe owlish. By pry of the invention, Luke smoke solution Jan ye aye that have the equivalent coloring debility of highly concentrated tar-~eplete~ liquid Sue solution derived prom an as key hut a high eolori~g ability it Tess trout an undesirable corresponding increase on tube phenol content. As one by the light ts~ns~ttan~e data Abe expel that follow. rely ~11 of the tar were abeyant from the Joy So epaulet Luke owe product produced my the aye of toe invention. It it expected that by rice of tube ln~ent~on. tar-aepleted loud aye solution having a light tr~n~it~dnce `
of sty Lowe recent preferably at least 80 Z7~69~

percent, more preferably at least 90 percent, can be produced. In addition, a portion of the acids, the principal one being acetic acid, in the generated smoke vapor remains in the waste gas stream, so that the concentration of undesirable organic acids in toe tar-depl~ted liquid smoke product may be reduced.
The tar-depletad, liquid smoke composition of this invention, whether unneutsalized or neutralized, is then applied to a food cawing. The food casings that are suitable for use in the invention are tubular casings, and preferably tubular solely to casings, that are prepared by any one of the methods well known in the art. Such casings are generally flexible, thin-walled 6eamles~
tubing formed of regenerated cellulose, cellulose ethers such as hydroxyethyl cellulose, and the like, in a variety of diameter. also suitable are tubular cellulosic casings haying a fibrous reinforcing web embedded in the wall thereof, which are commonly called "fibrous food casing", as well as ~ellulosic casings without the fibrous reinforcement, herein referred Jo as "non fibrous"
cellulosic casings.
Casings conventionally known as "dry stock casing" may be used in the practice of this invention. Such casings generally have a water content within the range of from about 5 to about 14 weight percent water for non fibrous casings, or from about 3 to about weight percent water for fibrous casing, based on the total weight of the casing including water.

. I , . .

Casings conYent~onally known as "gel stock casings" are casings which have higher moisture contents than the aforementioned casings wince they have not been previously dried. such casings may also be used in the practice of this invention. Gel stock annex, whether fibrous or non-fibrous, are the type exhibiting the aforementioned tarring problem when treated by as-is, tar-containing liquid stoke.
Toe tar-depleted liquid smoke solution of the invention may be applied to the outer surface of the tubular casing by passing the casing through a bath of the liquid smoke solution. The liquid smoke is allowed to soak into the casing prior to doctoring off any excess liquid smoke by passing the casing through squeeze rolls or wipers, and the like, for an amount of time sufficient for the cawing Jo incorporate the desired amount of smoke coloring and smoke flavoring constituents. The process of passing the casing through a treatment bath, also referred to in tube art as a "dip bath" or a "dip tank," may also be referred to in the art as a "dipping" step. The liquid smoke of the invention may alternatively be externally applied to the cawing by method other than dipping, such as spraying, brushing, roll-coating, and the like.
Alternatively, the tar-depleted, liquid smoke composition of the invention may be applied to the internal surface of the casing by any of several well-known procedures such as those described in United States Patent 4,171,3~1, issued October 16, lg79 to Chit. These include slugging or bubble issue coating, spraying, and coating while shinning. The slugging method for coating the inside of a casing involves willing a portion of the cawing with the coating material, Jo that the slug of coating material generally resides at the bottom of a "U"
shape wormed by the cawing being draped over two parallel rollers, and then moving the continuous indefinite length of cawing so that the slug of coating material remains confined within the casing, while the casing moves past the 61ug and is coated on its inside wall by the coaxing material contained within the slug.
One method of treating the casing with the smoke solution of the invention is shown in Figure 3. In Figure 3, a flattened, tubular, soliloquy sausage casing 10 it externally treated with the smote composition ox the invention during its passage over lower and upper guide rolls 13 through dip tank 11 which contains the liquid smoke solution 12 of the invention. The casing pauses o'er lower and upper guide rolls 14 after exiting the dip tank, and then passes between squeeze rolls ZOO which minimize any excess carry-over ox the liquid smoke composition. The total contact time of the casing 10 with the liquid smoke solution 12 will determine the amount of smoke coloring and smoke flavoring constituent of the tar-depleted, concentrated, liquid smote composition that the casing will incorporate. Tube total contact time it measured from point A to point B in Figure 3. Aster the casing passe through squeeze rolls 20, it passes over guide roll 23 and is wound up on roll 24. The ;27~,9~

cawing is when sent on to further conventional processing, including conventional humidification, a may be required, and conventional whirring.
The embodiment illustrated in Figure 4 differs from that illustrated in Figure 3 in thaw in Figure 4 the casing after pausing through squeeze roll 20 is pasted into a heating and drying clamber 21, Byron it is dried to the proper moisture content. The casing it inflated by a bubble of air maintained in a relatively fixed position between squeeze roll 20 and 22 by the sealing action of rolls 20 and 22. The heating chamber 21 can be any type of heating device, such a circulating hot air chambers, which will dry the sausage casing to the proper moisture content. After the cawing passes out of the heating chamber 21 and through squeeze rolls 22, it puffs over guide roll 23 and it wound up on roll 24. The casing is then sent on to conventional further processing, including conventional humidification, as may be required, and conventional whirring.
The embodiment illustrated in Figure 5 direr from that illustrated in Figure 4 in thaw in Figure 5, the cawing is dried in a flat condition while paying over guide rolls 25.
A preferred method for applying the tar-depleted liquid smoke solutions manufactured by the method of the invention it by a method wherein the exterior wall of a cawing it coated by moving tube cawing through an inner opening of a firs flexible and resilient means which dipoles the opening edge while liquid is applied by rubbing 3L~Z~6~3~
.

- I -contact. The liquid coating it then smoothed by move mint through the inner opening of a rotating second flexible and resilient means. this method and apparatus incorporating this method are described in United States Patent 4,356,218 issued on October 26, 1982, to Chit et at.
Therein the apparatus is described as an apparatus for liquid coating the exterior wall of an inflated flexible tubing during its longitudinal movement comprising: pa) first flexible and resilient mean with an inner circular opening having slightly smaller diameter than the diameter of the inflated flexible tubing exterior wall, the first means being transversely positioned relative to the tubing axis and arranged such that the inflated flexible tubing may be moved in its longitudinal direction through said inner circular opening, so as to displace the circular opening edge while maintaining rubbing contact therewith: by means for supplying said liquid to said first means tax for distribution thereby, so as to be applied to the longitudinally moving inflated flexible tubing exterior will during said rubbing contact: (c) second flexible and resilient means with an inner circular opening, the second means being rotatable around the opening center and the opening having slightly smaller diameter than the diameter of the inflated flexible tubing exterior wall, said second means being tran6ver6ely positioned relative to the tubing axis and adjacent to, but spaced downstream from the first means (a) with respect to the longitudinally moving tubing such that the tubing 69~

with the coating on its external wall may be moved through said inner circular opening of said second means so as to displace the rotating circular opening edge while maintaining rubbing contact therewith for smooching the applied liquid on the tubing exterior wall as a film of uniform thickness;
and (d) mean for rotating said second meanfi I
around the tubing axis during it longitudinal movement through said second means so as Jo maintain said rubbing contact while smoothing said liquid into a continuous film of substantially uniform thickness on the tubing exterior wall.
The method is described as a method for coating the exterior wall of a longitudinally moving inflated flexible tubing with liquid kippering the steps of lea) continuously moving toe inflated flexible tubing in the longitudinal direction along a straight line; (b) providing first flexible and resilient means with an inner circular opening of slightly smaller diameter than the diameter of the inflated tubing exterior wall: (c) supplying liquid to said inner circular opening of the first means:
(d) moving said inflated tubing through said inner circular opening of said first means and maintaining rubbing contact with the opening edge Jo as to displace said opening edge and simultaneously apply said liquid to, and distribute toe applied liquid around the inflated tubing exterior wall; (e) providing second flexible and resilient means with an inner circular opening of slightly smaller diameter Han the diameter of the inflated tubing exterior wall; (f) rotating said second mean around ....

I

it centerline axis: and (go moving said inflated tubing with said liquid applied on it exterior wall through the rotating second means inner circular opening and maintaining rubbing contact with the opening with the opening edge 80 a to displace said opening edge while 6imultaneou~1y smoothing the liquid coating as a continuous film of substantially uniform thickness on the tubing exterior wall.
It it to be noted what the ~ar-depleted liquid smoke company which it applied or "coated" on the cawing surface, whether externally or internally, doe not exist solely as a surface moating. Smoke color, odor and Flavor contusions which are coated on the surface penetrate the cellulosic structure of the cawing as the cellulose absorbs the smoke solution. Inspection of the cross-section of the casing wall discloses a dolor gradation across the casing wall, with the Moe treated surface having a darker color than the color on the surface on the opposite side of the cawing Hall. Accordingly, as used, herein, the term kowtowing or "coated" it meant to apply to a casing wall that it not only coated with smoke constituents but Allah impregnated with smoke con6tituent6.
The coated cawing may be whirred by conventional methods, or prior to shinning, it may be dried Andre humidified to a water content suitable for whirring and/or further processing.
The need for conventional drying and/or humidification after treatment with the liquid smoke composition of this invention depends on the water content of the cawing after treatment and the type Lo 276~0 - 37 _ of casino. If the casing is a nonibrous casing, a water content within the range of from about 11 to about 13 weight percent water before whirring, and between about 14 and 18 weight percent aster whirring, is typical. For fibrous casings, a water content within the range of from about 5 to about 7 weight percent water before shinning is typical, and after shinning the water content is typically in the range of from about I to 35 weight percent, where the percentages are bayed on the total weight of casing including water.
Thy liquid smoke compositions of the invention may also contain otter ingredients which may be suitably used in treatment of a tubular food cawing, to which the smoke constituents are applied, e.g., glycerine and/or propylene glycol, and the like, which may be used as humectants or softening.
agent.
Other ingredients which are normally used id the manufacture of, or for further treatment of the food Congo, e.g. cellulose ether and mineral oil, may also be prevent in the casing if desired.
and they may be used in the tame manner and amounts as if the liquid smoke composition of the invention Tad not been used.
In particular, agents for improving the pee lability of the casings from food products such as sausage, e.g. frankfurters, bolognas and the like, may be optionally coated on the internal surface of the Congo before or after the external application of tar-depleted, concentrated, liquid smoke composition to the casing and before or during I

whirring. If the tar-depleted liquid smoke is applied to the cawing internal surface, the pee lability agent is preferably applied irrupt. Such peelabiliey enhancing aqentC include, but are not limited to, carboxy~ethyl cellulose, methyl cellulose, and other water soluble cellulose ethers, the use of which it disclosed in United State Patent 3,898,348 issued August 5, 1975 Jo Chit, et at.; "Aquapel", a trademarked product, made by Hercules, Inc., ~ilmington9 Del., comprising alkyd kitten divers, the use of which it further disclosed in United States Patent 3,905,397 issued September 16, 1975 to Chit; and "Quilon", a trademarked product, made by E. I. Dupont de Numerous Co., Wilmington, Del., comprising fatty acid Cromwell chlorides, the use of which it further disclosed in United States Patent 2,901,358 idea August 25, 1959 to I. F. Underwood et at.
The pee lability 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, or example, the pee lability enhancing gent can be introduced into the tubular cawing in the form of a ~slugll of liquid, in a manner similar to that disclosed, for example, in United States Patent 3,378,379 issued April 16, 196B
to Shiner et at. Advancing the casing past the liquid slug coats the inner Ursa thereof.
Alternatively, the pee lability enhancing agent may be applied to the internal surface of the casing through a hollow mandrel over which the cawing it Lot advancing a, for example, a shinning machine mandrel in a manner similar to that described in United States Patent 3,451,827, issued June 24, 1969 to Bridge ford.
The method of this invention it Allah suitable for producing a printed casing e.g., a cawing having an insignia, trademark, lettering, and eke like printed thereon, having smoke coloring and smoke flavoring constituents incorporated therein.
Exemplary printed casings are disclosed in United State Patent 3,316,189, issued April 25, 1967 to Adams.
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 ye of non fibrous and fibrous casings which are preferably easy to peel from the food product, either by the food processor before sale Jo the cufitomer or by the consumer, "dry sausage" cawing preferably adheres to huffed product during and after prove King. "yeomen," a trademarked product, made by Hercules, Inc., which it a polyamide epichlorohydrin resin, the use of which it further disclosed on United States Patent 3,378,379 issued April 16, 1968 to Shiner et at., may optionally be coated on the internal surface of a casing treated with the smoke composition of the invention to improve the adhesion of the casing Jo food product processed therein.
The casings treated with toe liquid smoke compositions of this invention can then be used in conventional processes for the processing of Lo 0 sausages and the Lowe and the smoke flavor and color constituent are transferred to the food stuff encased in the casing.
The aqueous tar-depleted liquid smoke ~olution6 of the invention can be used to maze a smoke flavored cereal product, which can be used as a additive to food. This is accomplished by admixing the aqueous Sar~depleted liquid smoke with a cereal, such as Walt, and drying the mixture. A
suitable method is di6clo~ed in United State Patent 3,177,077~ issued January 7, 1983 Jo Hollenbeck.
The aqueous tar-depleted liquid smoke solutions of the inversion can be used to make a smo~e-flavored edible oil. This is made by contacting tube aqueous tar-deple~ed liquid smoke of the invention with an edible oil and separating the oil phase from the aqueous phase to form a smoke-flavored edible oil. A suitable method it disclosed in United States Patent 3,~80,446, issued November 25, 1969 to Hollenbeck.
The invention will now be Gore clearly understood by reference to the hollowing example which art jet forth as being merely illustrative of the invention and which are not intended, in any manner, to be limitative thereof.
In the following examples, the phenols and carbonyl content of liquid smoke were determined by the following procedure. All the sample to be evaluated were prepared by filtering them through a Whitman No. 2 filter paper or equivalent, and refrigerating them as soon as possible after preparation to void possible polymerization. All I

samples were diluted with distilled water it two steps. In the first step 10 milliliters of the sample were diluted to a total volume of 200 milliliters, and in the second step 10 milliliters of the solution from the first step were further diluted to a total volume of 100 milliliters. For the determination of the phenols, 5 milliliters of the solution from the second lop were further diluted in a third step with distilled water to a total volume of 100 milliliters. For carbonyl determination, 1 milliliter of the second solution was further diluted with carbonyl-free methanol to a total volume of 10 milliliters.
The procedure for the determination of the amount of phenols was a modified method for detecting toe amount of phenols as 2,5-dimethoxyphenol bayed on the procedure described by I. W. Tucker in "Estimation of Phenols in Meat and Fat", JACAC, XXV.-779 (1942).
The reagents used for determination of the phenols were 1. Boric acid-potassium chloride buffer having a pi of 8.3, made by diluting to 1 liter with distilled water a. 125 milliliters of 0.4 Molar boric acid solution, b. 125 milliliter of 0.4 Molar potassium chloride solution, and c. 40 milliliters of 0.2 solar sodium hydroxide solution, 2. 0.6 weight percent sodium hydroxide solution, I

- I -3. Color reagent, aye my oiling 0.25 Roy ox N-2,6-triehloro_b~nzo~ui~one-flown 30 lotteries of ~ath~ol end Starr r~friqerator until use. and

4. 2,6~ et~o~yph~ol ( W ) Tudor a my Swahili a known ought of DUMP it ova mount ox distilled water to o'er solution ox between 1 and 7 ~ierogra~s~illiliter.
the detonation of eye phenolfi aye o~pli~hed by following toe 6~ep6 below in order;
1. 5 ~illiliter6 of liquid Sue Apple, or 5 qrs DUMP arrowhead, or 5 ~illlli~ar~ of distilled water (for use a blown ore aided to 5 aillili~er6 of pi .3 far 2. The OH aye audited to I unyoke itQr ox sodium Dydroxiae solution.
3. Just before us 1 milliliter of Abe dolor reagent aye tea to lo ~llliliter6 with it'll water and 1 alter of toe allotted color reagent Way Dow Jo toe text sample.
4. She color was allowed to develop for 25 nuts it root temperature.

5. The bourbons us determined at Dave l~nqt~ of I em in 1 I
~olori~eter tube. the spectrophoto~eter was S~ctroni~M20, Dva~lable prom aye end Lob, Rochester. New York.

6. A nerd curve Wow prepared Roy the area of the WIPE standard with Jo . ~2~7~g~
- I -absorbency as the abscissa and concentrations of the tendered a the ordinate. The equivalent concentration of phenol a DUMP in the liquid smoke applies were interpolated from this curve.

7. The amount of phenol a DUMP
concentration in mg/ml in the liquid smoke ampule were calculated by using the equation, ppm DUMP (from to curve DO X 0.001 - - = DUMP gone.
vol. fig. smoke sample I
where "DO" in the above equation it toe sample dilution factor (400), and "0.001" it a factor to convert ~icrogram6 to milligram To calculate the my of phenol a DUMP in a gram of liquid smoke, divide the above result by the weight of 1 milliliter of liquid smoke.
The procedure for calculating carbonyl compound was a modified Lappan-Clark method for determining the equivalent amount of 2-butanone based on the procedure described in their article "Calorimetric Method for Determination of Tess of Carbonyl Compounds", Anal. Chum. 23, 541-542 (1959). The reagents used were 1. Carbonyl-free methanol, prepared by adding 5 g of 2,4-dinitrophenylhydrazine (DIP) to 500 milliliter of methanol and a few drop of Hal, refluxing for three hour, and then distilling, . .
.... . . . .. _ . . . . . .

~2~69i~

- I -2. DIP 601ution, made by disallowing twice recrystallized DIP in carbonyl-free methanol to form a saturated solution (Solution way stored in refrigerator and prepared fresh every two week. It was prewarmed before use to insure saturation.), 3. KOCH solution, made by dissolving 10 g KOCH in 20 milliliters of distilled water and diluted to 100 milliliter with carbonyl-free methanol, and 4. 2-butanone (methyl-ethyl-ketone) (ME standard solutions, prepared by adding known amount between 3.0 Jo 10 my of ME in 100 milliliters of carbonyl-free methanol tusked to make standard curve).
The procedure used for determining the amount of carbonyl compounds was as follow:
1. To 25 milliliter volumetric flask containing 1 milliliter of DIP
reagent add 1 milliliter of diluted liquid smoke solution, or 1 milliliter of standard R 601ution, or 1 milliliter of methanol (for reagent blank), 2. Add 0.05 milliliter of concentrated Hal to all 25 milliliter flask, mix content of each, and place in a water bath at 50C for 30 minutes, 3. Cool to room temperature and add 5 milliliter 6 so KOCH solution Jo each, 4. Dilute contents of each flask to 25 milliliters with carbonyl-free methanol, ~2~g~

5. Using a Spectronic 20 6pectrophotometer, available from Bausch and Lomb, Rochester, New Yore, and 0.5 4 inch (1.27 10.2 cm) cuve~tes, calibrate the ~peceropho~ometer by reading at a Dave length of 480 no against the methanol blank and jetting the absorbency at 0.
6. Using data for MCKEE. ploy ab~orban~e Years ME concentration for standard curve, 7. Interpolate concentration of ME
equivalent in diluted liquid McKee solutions from this curve,

8. Calculate the carbonless concentration as my ~EK/lOOml liquid smoke by the following equation;

my From to curve DO go ME per = 100 I fig. smoke 100 ml where "DO" it the sample dilution factor (200). To calculate carbonyl6 a my UæK/g liquid smoke, divide the result of toe above equation by the weight yin gram of 100 milliliters of the smoke being tested.
The Color frowning Index way determined as follows:

I Prepare a phthalate buffer 601ution (pi 5.5) by diluting to 1000 milliliters ~ieh distilled water, 500 milliliters of 0.1 potassium hydrogen phthalate and 76 milliliters of 0.5 H Noah;

.. .

lz~6g~

(2) Prepare a 2 percent Gleason buffer solution by dissolving 2 Russ of Gleason in 100 milliliter of the pi 5.5 ~hthalate buffer;
(3) Add 10 milliliters of the phthalate buffet solution to a 20~150 mm test tube;
(~) Add 10 milliliters of the Gleason buffer solution to another 20~150 mm test tube;
US) Add 1.0 milliliter of distilled water and 10 milliliter of Gleason to serve as a reagent blank;
(6) Cap the tubes wit marbles and warm the tubes in a boiling water bath for 5 minutes:
~73 Dilute toe liquid smoke solution to be tested with methanol at a ratio of 1 part liquid smoke to 50 part methanol;
o the tube containing the Gleason buffer (reaction sample) and the phthalate buffer only tunreacted control) add 1.0 milliliter of the diluted liquid smoke;

(9) Allow the color reaction to proceed at 100C for exactly 20 minutes, after which the tubes are removed from the boiling water bath and cooled in an ice bath for 2 minute;

(10) Using a ~pectrophotometer with cuvette~ 0.5 inches (12.7 mm) diameter or equivalent, determine the optical density of the reaction sample and the unrequited control at a wave length of 400 no, by ~227G9~

-- I _ rod Ann the glycine-water plank jet at optical density of O.
(11~ From e optical eons ox the r~3c~d lapels (OUR) and the opSi~al Nat ox Lowe reacted control (ODE) ~eter~lne the Color Brovninq Peg t~BI ) grow toe following formula:
t:BI - 1 (OUR - ODE) O. lo ] DO So O. 65 .
whose UP is tile salDple ablution factor (JO).
Lowe Color Browning Index it azure of toe quantity ox potential color forming substances profanity per us of liquid owls.
Toe color etrlc Rowley "L" an aye or sausage surfaces were obtainer using a aaraner~xL-23 Tris~i~ult~6 Calorimetry to a 1 centimeter aperture s~tasldardizea iota write plate, all in accordance it the tenured operating priors ~escribea in Use instruction manual or the aaraner ~L-23 Tr1fitl~ulus Calorimeter. Webb Jo commonly Sue on to industry for ye ~ea~urefflent of dolor.
Five frankfurter frond each liquid Dallas treated sample worry eta. ~qea6uralDent~ were aye Bout 2.5 eenti~D2ter~ from act end ox tube franls~urter~
and it tube idyll. Tube 15 Yule obtained for the AL" Noah I" Yule were a~rer~ged together to obtain the isle ire. L" value represent liQ~tn~ss no arcane. eke sigher tube AL" value the lighter thy color. The a" .ralue~ r~preljent wryness, thy Hebrew to a value Sue rudder the oily .
I~LWLE I
This zeta onstrates the Roy of toe inv~t~on 1:18~ batch prows. The apparatus . .

69~

used it illustrated it Figure 2. Hardwood audit available from Franz Company hardwood Sawdust, Milwaukee, Wisconsin, way thermally decomposed Jo generate Moe vapor by placing 775 grams of sawdust in a kiwi generator 71 comprising a 6 liter metal container capable of being sealed and heated. The metal container way heated over a Bunsen burner 72, and the generated smote vapors were led from the generator via stainless steel tubing 73 to an abrasion vessel 74. The abrasion vessel 7g comprised a one liter Erlenmeyer flask 75 . The Moe vapor entered the absorption vessel 74 through a wintered glass sparg2r 76. the absorption vowel 74 was f tiled with 600 ml ethylene dichlorides ~dichloromethane) and 100 ml water, and way stirred throughout the abrasion to increase the gas-liquid contact. The Moe generation way continued as long as the kiwi generator 71 was capable of generating Moe (about six Herr. A the smoke vapors were generated, tube pressure forced them into the abrasion vessel 74. The organic solvent, ethylene dichlorides phase 77 in the absorption vowel 7q absorbed eke tarry hydrocarbon components, becoming darker in color as the absorption prows proceeded. The aqueous phase 78 absorbed the color, flavor, and odor constituents of the vapor. The absorption vessel was equipped with a glass water cooled condenser snot shown) to recondense evaporated water and ethylene dichlorides vapor.
During the abrasion process, the temperature of the organic phase 77 way at about 40C, and aqueous phase 78 way Allah at about 40C. The exit gay from ~L;2;Z~69~1 - 4g -the absorption vessel was found Jo have no odor and was colorless. This procedure way repeated on two subsequent day with a fresh charge of sawdust on each day, but the original charge of ethylene dichlorides and water was retained in flask I during all three days. The aqueous phase 78 was separated from the ethylene dichlorides phase 77 by recantation to give a measured 200 milliliters of aqueous tar-depleted liquid smoke.
A sample of the tar-depleted liquid smoke aye made and analyzed. The results of the analysis are summarized in Table A. Also shown in Table A
are the typical value of an as-is liquid smoke coarsely C-12) for comparison.

TABLE A

Invention As-Is CBI 11.0 10.5-12 Light Transmittance So) 100 0 Phenol mug 1 13-20 Acids (~) 11.3 11.5-12.5 The visual color of the tar-depleted liquid smote was a very light amber color. The light transmittance was 100 percent, indicating a total depletion of tar constituents. The coloring ability a shown by the CBI it comparable to an as-is liquid smoke and the content of the phenols is significantly less.
This example demonstrates that the method of this invention may be used to prepare a ~2%~69i~) -- so --tar-depleted liquid smoke solution having coloring ability comparable to commercially available as-is liquid smoke solution also demonstrate the low phenol content and the low tar-content, as shown by the fight Transmittance, of the liquid smoke solution of the invention as compared with assay liquid smoke solution.
EMPLOY II
The tar-depleted liquid smoke of Example I
was applied to a casing and the cawing was used to make a sausage product. The tar-depleted liquid smoke way partially neutralized at a temperature of about 18C to a pi of about 5 and was applied to a nonfibrou~ gel stock easing using the method and apparatus described in the above-cited U. S.
4,356,216. The casing way dried, shinned and then stuffed and processed by conventional Taipei of cooking, cold water showering, and chilling, but without the conventional step of smoke treatment.
In Table B is shown the meat formulation used.

TABLE B
Inqredient6 Weiqhtfk~) Beef Chuck 22.7 Regular Pork Trim 22.7 attires 9.1 Salt lo Spice 0.5 Prague Powder (Sodium Nitrite) 0.13 .. . . ..

go - so -Sue Elro~s~siDg ennui were ~u~fic~e~t Jo Sue thy trainer of Nikko color, odor Noah Lowry ~o~titue~ Prune the Congo to the riced usage The aye were pull my conventiollal ethos and eoloriLmetr~c Allah wore obeainea.
These ye ~u~ar~zed blow in Table C. Alto Boone in Table C ore values obtained frond sausages treated bit an aye l~guia joke (Charlie C-12), a tar-a~pleted lug smoke jade from an liquid joke ~Ctlar601 ~-12i u6~ng the solvent extraction prows disclosed on the above-~itea U. 5. Ser. No 4,431,033 (501. lot ), and an ull~moked control, using on untreated cawing. The toe liquid stoke Lyle on produced by the solvent extraction prows was partially neutralized to a pi of about 4 at a temperature less than about ~0C.

TABLE C
a, a Invention 15 . 65 Assay 49.~6 14.B9 ct.S0.09 15.24 Control ~0.~5 1~.57 Tubs exafflple ooze that the tar-depleted loud joke of Tao invention i~part6 color to a owe Rudy ho is æub6tantially equivalent to that parted by assay liquid kiwi end tar-aeple~ed liquid Sue aye from on I liquid woks by a ~ol~nt extraction process.

69~

EXAMPLE III
The purpose ox this example it to compare the chemical characteristics of the tar-depleted liquid smoke produced in accordance with this invention with whose of liquid moves produced by other ~ethod6.
Using the apparatus and method described in Example I, two text run were made. In a run according to the invention, the absorption vessel 74 contained 700 grams of ethylene dichlorides and 100 grams of water. In a comparative run, the abrasion vowel 74 contained 700 grams of water and no ethylene dichlorides weft used. Smoke generation was conducted in each text for about 3.5 hours.
For the run according Jo the invention (Inanity, the ethylene dichlorides layer ab60rbed the tar components of the smoke vapor and the awry layer absorbed the color, flavor and odor constituent of the vapor. The temperature of the two liquid layer in the abortion Ye Mel 74 was about 40C. The aqueous layer was separated from the ethylene dichlorides layer by recantation and the resulting ear-depleted liquid smoke (220 trams) was analyzed.
In the comparative control run, the smoke vapors produced during the smoke ~eneraeion procefis were only ab60rbed by the water, resulting in an aqueous mixture of tarry hydrocarbon con~eituent~
and smoke color, flavor and odor constituents. the temperature of the aqueous layer was about 100C.
The tarry constituents beetled out and the aqueous ~L~Z769C!

layer containing the liquid smoke constituents was separated by recantation and then analyzed (Coup.
A). Since this liquid smoke was v rye dilute compared to the tar-depleted liquid smote produced according to the invention, it was concentrated Jo a concentration weight ratio ox 2.5:1 by evaporating it at a temperature of 50C at a pressure of 20 mm Hug. The resulting 220 grams of concentrated liquid smoke was analyzed (Coup. B). The results of the analysis is shown in Table D. Also shown in Table D
are values typically found or as-is liquid smoke solution and the values for the liquid move as disclosed in the examples of the above cited U. S.
blue, to Suits, et at. (Suits).

TABLE D

Sample CBI Light Trans. Curb. Phenols Acids percent) mug mug I%) _______________________._________________________ Invent. 9.8 95.9~6.3 1.514.9 Coup. A 6.0 98.072.5 5.65.6 Coup. B 7.3 97.5103.3 8.09.6 swept - - 25 - 81 1.6-2.3 2-6.4 As-Is 10.5-12 070 -100 13-2011.5-12.5 The data of Table D demonstrates the advantages of the tar-depleted liquid smoke solution of the invention as compared to other liquid smoke solutions.

. .
I

The liquid smoke 601utions made by the prior art process, wherein smoke vapor it absorbed into an aqueous medium, (Coup. A, Coup. I, and As-Is) all show a significantly higher convent of phenols than the liquid smoke of the invention.
This low content of phenols on the invention was achieved in addition to the achievement of a favorably high content of the carbonless. The high content of the earbonyls in relation to the content of the phenols Allah eo~pares Favorably with the liquid smoke concentrates disclosed in Suits, et at.
The percent of the phenols in the composition of the invention was only 1.6 percent of the content of the carbonyl~ (1.5 mug phenols mug carbonless).
This it equivalent to a ratio of carbonless So phenols of 65:1 on a 2-butanone/DMP basis which it 84:1 on an acetone/phenol basis. This how significant improvement over the compositions disclosed in Suits, et at. which have a carbonyl to phenol ratio of (17-~7):1 on an acetone/phenol basis. This example demonstrates what a desirable high content ox the carbonyl coloring constituents can be achieved without necessarily resulting in a corresponding undesirable it content of the finlike flavoring constituents.
Increased coloring ability does not necessarily correspond to increased flavoring ability. However, the process of the invention produces a liquid smoke solution highly effective for its coloring capability, and although it has a low finlike content, its flavoring ability is sufficient for commercial applications.

Typically, liquid smoke ~olution6 produced commercially by the prior art process of absorbing smoke appear into an aqueous medium, and which have a carbonyl content comparable to Coup. A and Coup.
B, hove a very low light transmittance. This it shown by comparable commercially available assay liquid smoke solution which have a light transmittance of I The samples Coup. A and Coup.
B would normally be expected to also have a very low light transmittance. However, due to a limitation of the cooling capacity of the condenser, the prior art process of Coup. A and Coup. B was run at a higher than normal temperature of 100C. In prowesses of this kind an abrasion temperature between about 20C and about 45C is normally desired. The higher temperature of this example caused a higher proportion of organic acids Jo be lost by evaporation, as shown by the lower then expected acid content of Coup. A and Coup. B. The acids in a liquid smoke 601ueion syllables the tars in the liquid Moe 601u~ion. In Coup. A the acid content was insufficient to 601ubilize the tar, and the main portion of the tars jell out of 601ution before analysis of Coup. A. Thirty trams of solid precipitated tars were removed before the the analysis of Sample Coup. A and the 6ub~equent concentration of Sample Coup. A to form Sample Coup.
B.
A was shown above, the tar-depleted liquid smoke produced in accordance with the present invention had coloring ability, a shown by the CBI, comparable to that of commercially available as-is liquid smote.

~L~2~69~

- I -EMPLOY IV
In this example, a non fibrous cawing having a flat width of about 30.0 mm to about 31.8 mm was dipped in eke liquid smoke solution of Example III
for 30 seconds. About 10 milligrams of liquid smoke was absorbed per square inch of casing surface (1.55 milligrams per square centimeter). The treated casing was dried and stuffed by conventional methods with an egg albumin emulsion and cooked for 2 hours at 100C in a laboratory oven. The egg albumin emulsion contained about 35 wt.% powdered egg white albumin (Raft, Ionic, about 12 White of a commercial powdered cellulose (Solfaflock, Brown Co.). and about 53 White water. The consistency was that of a thick pave, similar Jo typical meat emulsions. The color transferred to the egg albumin emulsion it a measure of the coloring ability of Cue liquid smoke solution for protein substances. Upon visual inspection of the final product, very good smoke color way exhibited by the products processed in the casings treated with the liquid smoke of the invention (Invent.) and the concentrated liquid smoke solution made by a prior art prows (Coup.
By. The sample made by the prior art process (Coup.
A) exhibited only iota smoke color when compared with the white control sample.
EMCEE V
This example demonstrates an embodiment of the invention using a pilot scale process. The apparatus used is illustrated in Figure 6. Sawdust vat fed into a conventional smoke generator snot shown), essentially the same as that as described in ~.2;2~

United States Patent 3,106,473. The generated smoke way conducted through a duct 101 into the bottom of a counter-current absorption unit 102, and was then drawn wick a blower (not shown) upwardly and out of the absorption unit 102 through duct 103. The absorption unit 102 was a column about 1 meter high and 15 centimeters in diameter and it contained a bed 104 of packed bent saddles. ethylene chloride was introduced into the top of the absorption unit 102 through conduit 105, and then through a spray nozzle 106, after which it flowed downward and countercurrent to the upward flow of the smoke pausing thrush the absorption unit 102. While the smoke vapor was flowing upwardly through the absorption unit, water in toe smoke vapor condensed from the smoke vapors and also Plowed downwardly through the absorption unit 102, countercurrent to the smoke vapor, thereby absorbing color, flavor, and odor constituents from the smoke vapor as it progressed. The ethylene chloride, also flowing counter currently to the smoke vapors, extracted tar from the smoke vapors and tars which may have been absorbed in the condensed waxer. The condensed water and the liquid ethylene chloride then passed, as separate foe, out of the column through conduit 107. From conduit 107 the two phase liquid paused into a separator 108 in which the liquid separated into a less dense phase 109 comprising an aqueous liquid smoke, containing mainly smoke color, flavor and odor constituents, and a denser phase 110 of ethylene chloride, containing mainly smoke tars. the ethylene chloride pasted from the LO I

separator 108 through conduit 111 Jo a color 112, and recycled via conduit 113, 105 and pump 114 into the absorption unit 102. Lone 111, 113, 105 were inlaid tunnels steel pipe. The aqueous liquid smoke 109 left the operator 108 by way of a overflow 115 and collected as a jar depleted liquid smoke product of the invention.
Twenty-four pound (10.9 kg) of maple audit were continuously fed to the smoke generator with the strew fed during the test. The temperature of the smoke vapor entering the abrasion unit through duct 101 way about 250F (120C) at the beginning of the test and rove to about 3754F
t190C) at the end of the test. About 65 pound (29.5 kq) of dry ice were used in eke cooler 112, to maintain the temperature of the ethylene chloride at between about 30F (-1C) and about 44F (7C) a it entered the absorption unit from line 105.
Initially there were 16 liters of Mullen chloride in the system. During the run, ethylene chloride was periodically added to make up for ethylene chloride vapor lout to the atmosphere through duct 103. A total of 24 liter of ethylene chloride wore used with 9.4 liter recovered at the end ox the run. The remaining 14.6 liter were 105~ a vapors through duct 103. The total amount of aqueous tar-depleted liquid Moe condensate obtained through overflow 115 way 2830 ml.
The text way begun by first starting pump 114 and equilibrating the temperature of the ethylene chloride to about 33F (1C). The smoke vaporfi were then admitted through duct 101 into toe ~2Z76~

adsorption unit 102. Ethylene chloride was added in 2 liter increments 45 minutes, 70 minutes, 100 minutes and 110 minutes after the smoke Vapors were admitted. Samples of the overflow of the aqueous tar depleted liquid smoke product of 400 ml, 900 ml, and Z50 ml were taken 45 minutes, 90 minutes and 125 minutes, respectively, after the smoke vapors were admitted. The samples were combined into one sample tin-) and analyzed. Part of the combined sample was concentrated (Cone.) to a weight ratio of 2:1 by evaporation at a temperature of 50C and at a pressure of 20 mm Hug, and the concentrated product was then analyzed. The results of the analysis are shown in Table E. the values not shown for the concentrated sample were not measured.
Table E
In. Cone.
Light Trans. (~) -60 Casbonyls mug 152 180 Phenols my 5 21.7 Acid (wt. I) 9 CBI 20 46.~
The above tar-depleted liquid smoke products (In.
and Cone.) were applied to a cawing and the casing was stuffed as in Example II. The "L" and "a"
values were measured for the food product stuffed in each casing as well as the "L" and "a" values for a food product stuffed in a control casing thaw was not treated with liquid smote. The results of the measurements are shown in Table F.

~22~

Table F
L a Ivy. Sly 1~.3 Cone. 46.6 lB.9 Cont. 55.5 17.0 This example shows how tar-depleted liquid smoke of the invention having good coloring ability can be produced in a continuous process. Also shown the absence of tar in the tar-depleted liquid smoke a shown by the light transmittance values.

Claims (36)

What is claimed is:

1. A method for preparing a tar-depleted liquid smoke solution which comprises (1) thermally decomposing wood in an oxygen-controlled atmosphere to generate smoke-vapors, (2) selectively solvent extracting the tars from the generated smoke vapors, and (3) absorbing the smoke vapors into an aqueous medium to provide a tar-depleted liquid smoke solution.

2. A method for preparing a tar-depleted liquid smoke solution which comprises (1) thermally decomposing wood in an oxygen-controlled atmosphere to generate smoke-vapors, (2) contacting the smoke vapors, water and an organic solvent having a solubility parameter greater than about 2.7, to form a tar-containing liquid solvent phase and an aqueous liquid smoke phase, (3) separating the liquid smoke phase from the the liquid solvent phase to provide a tar-depleted liquid smoke solution.

3. In a method for preparing a tar-depleted liquid smoke solution which comprises thermally decomposing wood in an oxygen-controlled atmosphere to generate smoke-vapors and condensing the smoke vapors into an aqueous medium, the improvement of selectively removing the tars from the smoke vapor by contacting the smoke vapors with an organic solvent having solubility parameter greater than about 2.7.

4. The method of Claim 2 wherein the smoke vapors are contacted with water and a solvent in a single contacting zone.

5. The method of Claim 2 wherein the smoke vapors are contacted with a solvent in a first contacting zone and with water in a second contacting zone.

6. The method of Claim 2 wherein the tar-depleted liquid smoke is neutralized to a pH
greater than about 3.

7. The method of Claim 6 wherein the tar-depleted liquid smoke is neutralized to a pH
between about 3 and 6.5.

8. The method of Claim 7 wherein the tar-depleted liquid smoke is neutralized to a pH
between about 3 and 5.

9. The method of Claim 2 wherein the tar-depleted liquid smoke solution has a light transmittance greater than about 50 percent.

10. The method of Claim 9 wherein the tar-depleted liquid smoke solution has a light transmittance greater than about 80%.

11. The method of Claim 10 wherein the tar-depleted liquid smoke solution has a light transmittance greater than about 90%.

12. The method of Claim 11 wherein the tar-depleted liquid smoke solution has a phenol content of about 10 percent of carbonyl content.

13. The method of Claim 2 wherein the tar-depleted liquid smoke solution has a phenol content less than about 10 percent of the carbonyl content.

14. The method of Claim 13 wherein the tar-depleted liquid smoke solution has a phenol content of about 1.5 percent of the carbonyl content.

15. The method of Claim 2 wherein the temperature of the organic solvent phase in step (2) is about 40°C.

16. The method of Claim 1 wherein the tar-depleted liquid smoke solution is further concentrated.

17. The method of Claim 2 wherein the tar-depleted liquid smoke solution is further concentrated.

18. The method of Claim 3 wherein the tar-depleted liquid smoke solution is further concentrated.

19. The method of Claim 16 wherein the tar-depleted liquid smoke is neutralized to a pH
greater than about 3.

20. The method of Claim 17 wherein the tar-depleted liquid smoke is neutralized to a pH
greater than about 3.

21. The method of Claim 18 wherein the tar-depleted liquid smoke is neutralized to a pH
greater than about 3.

22. The tar-depleted liquid smoke composition prepared by a method which comprises (1) thermally decomposing wood in an oxygen-controlled atmosphere to generate smoke-vapors. (2) selectively solvent extracting the tars from the generated smoke vapors, and (3) absorbing the smoke vapors into an aqueous medium to provide a tar-depleted liquid smoke solution.

23. The composition of Claim 22 wherein the smoke vapors are contacted with water and a solvent in a single contacting zone.

24. The composition of Claim 22 wherein the smoke vapors are contacted with a solvent in a first contacting zone and with water in a second contacting zone.

25. A composition of Claim 22 wherein the tar-depleted liquid smoke is neutralized to a pH
greater than about 3.

26. The composition of Claim 22 wherein the tar-depleted liquid smoke is neutralized to a pH
of between about 3 and about 6.5.

27. The composition of Claim 26 wherein the tar-depleted liquid smoke is neutralized to a pH
of between about 3 and about 5.

28. The composition of Claim 27 wherein the tar-depleted liquid smoke solution has a light transmittance greater than about 80 percent.

29. The composition of Claim 28 wherein the tar-depleted liquid smoke solution has a light transmittance greater than about 90%.

30. The composition of Claim 22 wherein the tar-depleted liquid smoke solution has a phenol content less than about 10 percent of the carbonyl content.

31. The composition of Claim 30 wherein the tar-depleted liquid smoke solution has a phenol content not greater than about 2% of the carbonyl content.

32. The composition of Claim 30 wherein the tar-depleted liquid smoke solution has a phenol content of about 1.5 percent of the carbonyl content.

33. The composition of Claim 22 wherein the temperature of the organic solvent phase in step (2) is about 40C.

34. A tar-depleted smoke colored and smoke flavored tubular casing which is made by contacting a tubular casing wall with a tar-depleted liquid smoke of Claim 22.

35. A method for preparing a tar-depleted smoke colored and smoke flavored tubular casing which comprises contacting a tubular casing wall with tar-depleting liquid smoke of Claim 22.

36. A method for preparing a smoke colored and smoke flavored foodstuff which comprises stuffing a tubular casing of Claim 34 with a foodstuff, and processing the resulting encased foodstuff under conditions sufficient to transfer smoke color and smoke flavor constituents to the encased foodstuff.