CA2121989A1 - Thermal abuse resistant egg - Google Patents
Thermal abuse resistant eggInfo
- Publication number
- CA2121989A1 CA2121989A1 CA 2121989 CA2121989A CA2121989A1 CA 2121989 A1 CA2121989 A1 CA 2121989A1 CA 2121989 CA2121989 CA 2121989 CA 2121989 A CA2121989 A CA 2121989A CA 2121989 A1 CA2121989 A1 CA 2121989A1
- Authority
- CA
- Canada
- Prior art keywords
- liquid egg
- egg
- liquid
- nisin
- amount
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B5/00—Preservation of eggs or egg products
- A23B5/005—Preserving by heating
- A23B5/0055—Preserving by heating without the shell
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B5/00—Preservation of eggs or egg products
- A23B5/005—Preserving by heating
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B5/00—Preservation of eggs or egg products
- A23B5/08—Preserving with chemicals
- A23B5/12—Preserving with chemicals in the form of liquids or solids
- A23B5/14—Organic compounds; Microorganisms; Enzymes
- A23B5/16—Microorganisms; Enzymes
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention involves rendering liquid egg resistant to thermal storage abuse by the addition of, for example, nisin thereto. This is particularly useful when done in combination with electroheating or some other highly effective pasteurization process.
The present invention involves rendering liquid egg resistant to thermal storage abuse by the addition of, for example, nisin thereto. This is particularly useful when done in combination with electroheating or some other highly effective pasteurization process.
Description
~IERMI~L A~U8E: RE8I8TANT EGG
The present invention relates to the field of enhancing the storage stability of perishable ~ood~.
Liquid egg pasteurized in accordance with minimal pasteurization times and temperatures using a conventional plate heat exchanger may have a refrigerated shelf life of somewhere between about 1 and 2 weeks. Refrigerated shelf life, as the term : implies, requires that the liquid egg be properly stored at refrigerated temperatures of under 45F and, preferably, under 40-F at substantially all times after pasteurization. If liquid egg pasteurized as described above were left on a counter at room temperature, even in a sealed container, it is unlikely that the liquid egg would remain edible for ' much longer than about 24 hours. of course, because ,; the egg is pasteurized, there is no threat of , 20 Salmonell~ infection. However, spoilage j microorganisms such as those of the family Bacillaceae " and of the ~amily Pseudomonas will grow prodigiously.
i~ A8 they multiply and grow, the egg is consumed and converted lnto bacterial waste. As a result, the egg be,comes vl~cous, acidic, and/or rotten smelling as well a~ unpalatable.
Some, like Dunn et al., U.S. Patent No. 4,695,472, sugge~t electrically stressing food by the u~e o~ hlgh ene,rgy, high current density ~le,ctric~l pulses and therea~ter, maintaining the electric~lly ,stressed ~ood under substantially sterile t condition,s and packaging 80 as to have an extended ~helr li~e. Preferably, the electrically stressed ~oodstu~fs are maintained and packaged under aseptic conditions, Dunn et o,l. suggest that the ~helf life tho resulting roodsturf can be improved by ad~usting the, temperature at which the foodstuff i8 treated. Further improvement in shelf life may be obtained by cooling the electric field treated liquid 2~1939 foodstuff to a refrigeration temperature of less than 50 F. Dunn et al. also illustrate that when liquid egg is heated to 58~C (below the temperature neces~ary for thermal pa~teurization of liquid whole egg according to the U.S.D.A.), by use of specific electrical pulses followed by storage at 50F, an increase in refrigerated shelf life is observed.
However, if the treated liquid egg is stored at below 40-F, the refrigerated shelf life of the egg extends to 28 days or longer.
Others, however, suggest adding various agents to the liquid egg to improve refrigerated shelf life. For example, bacteriocin, nisin, and other antibiotic-like preservatives have been suggested for use in connection with pasteurizing liquid egg so as to provide an extended rerrigerated shelf life. For example, as reported in Delves-Broughton et al., ~The use of the bacteriocin, nisin, as a preservative in pasteurized liquid whole eggn, Letters In Applied Mlcroblology, (1992), 15, 133-136, nisin used at levels of 5 mg per liter resulted in a significant increa~e in refrigerated shelf life of pasteurized liquid whole egg. Nisin also protected liquid egg ~rom the growth o~ B~clllus cereus.
or course, the sugge~tion of the addition of nlsin to egg is nothing new. For example, ~lAokburn et ~1., U.S. Patent No. 5,135,910 discusses the application of nisin compositions as a b~cteriocide rOr treating meats, especially poultry, egg~, che~se and rish and for treatment of rood packnging and handling equipment. ~lAckburn et al.
de~cribe that nisin has been applied effectively as a preservative in dairy products such as processed chee~0 and that the use o~ nisin to inhibit the growth Or cortain gram positive bacteria has been well do¢umonted. Bl~ckburn et al. suggest that by the co-administration of nisin and certain chelating or ~urfactant agents, the growth of gram negative . , .
-. ' : : ' : ' - ~219~.9 bacteria such as Salmonella tychimurlum, ~scheria coli and others can be controlled and greater activity towards certain gram positive bacteria such as L~steria monocytogenes can be realized. see also ~l~ckburn et al., U.S. Patent No. 4,980,163 which also suggests the use of ni~in and other bacteriocins in conjunction with food such as eggs.
Despite these technological advances in terms of refrigerated storage and extended refrigerated 6helf life, consideration of the problems as60ciated with thermal abuse resistance as well as methods of overcoming these problems have remained largely unexplored. It i8 known that liquid egg that has been pa~teurized, placed in an extended shelf life container and properly stored at 4C or under will last for elght weeks or longer. In fact, an extended refrigerated shelf life of 12 weeks or more i6 not uncommon. However, it is generally known that as the storage temperature of the liquid egg increases, a decrease in storage life is observed. The inventor has realized that, within limits, for every degree over 40'F that liquid egg is stored, one week of extended re~rigerated shelf life is compromised.
Thu~, lf extended refrigerated shelf life liquid egg ~5 having an antlcipated shel~ e of 12 weeks is re~rlgerated at 50-F instead of 40~F, the resulting egg ~hould have a shelf life of only about 1 to 2 weeks. Thus, a mere 10- change in temperature e~entially negates the entire advantage imparted by v~riou~ extended shelf life pasteurization and packnglng technlque6. As storage temperatures climb abovo 50-F, the resulting shelf life of the liquid egg iB reduced even further to merely a matter of days.
The present inventor has observed that when 3S properly rerrigerated and stored, extended refrigerated shelf life egg eventually goe~ bad and/or when spoilage is brought about by improper filling or contamination during filling, the resulting egg has a ... ~ ~ ,, . , . - . I . , ,." "-" . ;.. , , . . .. , ,.,- ~ .. . , , : , ., . . , . " .. ......
2~21~9 -4- ~
dark, almost brownish color. The pH stays approximately the same or, if anything, becomes more basic, and the material smells sour.
In contrast, when egg has been abused by being held at a temperature of above 40F for any length of time and more particularly, over 45~F, the color becomes a bright and uncharacteristically unnatural yellow, the pH generally drops to as low as 5.5 or below and the product thickens and becomes ,~ 10 viscous. Eventually, the material smells rotten. As a result, thermal abuse is a particularly important problem for consumers. While the egg may not smell - bad and may not have thickened or discolored ~u'~iciently to alert the consumer, its pH and 1~ bacterial content have changed such that the egg ~hould not be used. Often consumers find out about this only a~ter the egg has been incorporated into i other products or consumed.
3 The present inventor believes that, Bac~llu6 cereus and Enterococcus faecalis are ~ di~ficult to kill by certain pasteurization ç technique~. When these bacteria remain in liquid egg and the liquid egg i6 properly stored at 40-F or below, they generally remain dormant. In fact, they may not contribute to spoilage ~t all. However, when ~ ~torod at temperature~ above 40F, and more o~ten at j t~smperatures higher than 45F to about 50P, the ¦ growth o~ th~se di~ficult-to-kill bacteria becomes I ~extr~mely rapid. They can then play a proround role ~ 30 in egg spoilage.
i Manirestly, the considerations surrounding I tho problem o~ thermal storage abuse are extremely ¦ dirrerent than tho~e involved in extending the rorriger~ted shelr li~e o~ liquid egg. Moreover, whils, ao be~ore, the attention o~ the industry was ~ocused on providing method~ Or imparting an extended ! re~rigerated shel~ life, that ~ocus has begun to shi~t. Egg processors can control the way in which ~ ;
' ' 2 1 ~ 9 -5- ~
. ~ -, liquid egg is processed and by selecting particular methodologies and by the use of particular tvpes of extended shelf life packaging, can provide the consumer with pasteurized liquid egg having a re~rigerated shelf life of 3 months or more. However, proceesors can only control the quality of the egg so long as the egg remains under their specific control.
once a consumer has purchased the egg, the responsibility for proper handling and refrigerated storage fall upon the consumer. A few days of improper handling, particularly at temperatures approaching room temperature or above, can virtually eliminate all of the extended refrigerated shelf life that technology can provide. Of course, if the egg turns out to have spoiled prematurely, it is the processor who hears about it and who often must make good even though the reason for the premature spoilage resulted from improper handling and refrigeration on the part of the consumer.
The present invention provides a way to assist processors and users alike in ensuring the continued quality of the liquid egg throughout its intended re~rigerated shelf life by providing for varlous methods o~ imparting thermal storage abuse rooi~tance to liquid egg products.
It i8 an object of the present invention to provide liquid egg which i8 resistant to thermal otorage abu~e.
It i8 another ob~ect of the present invontion to provide liquid egg which will maintain a signi~iaAnt portion of ite anticipated extended rofrigorated ehelf life even after prolonged exposures to improper refrigeration conditions or otherwise elevatod temperature~.
3S It is also an ob~ect of the present lnvention to provide a method ~or imparting thermal otorage abu~e resistance to liquid egg.
.j :
// :
The present invention relates to the field of enhancing the storage stability of perishable ~ood~.
Liquid egg pasteurized in accordance with minimal pasteurization times and temperatures using a conventional plate heat exchanger may have a refrigerated shelf life of somewhere between about 1 and 2 weeks. Refrigerated shelf life, as the term : implies, requires that the liquid egg be properly stored at refrigerated temperatures of under 45F and, preferably, under 40-F at substantially all times after pasteurization. If liquid egg pasteurized as described above were left on a counter at room temperature, even in a sealed container, it is unlikely that the liquid egg would remain edible for ' much longer than about 24 hours. of course, because ,; the egg is pasteurized, there is no threat of , 20 Salmonell~ infection. However, spoilage j microorganisms such as those of the family Bacillaceae " and of the ~amily Pseudomonas will grow prodigiously.
i~ A8 they multiply and grow, the egg is consumed and converted lnto bacterial waste. As a result, the egg be,comes vl~cous, acidic, and/or rotten smelling as well a~ unpalatable.
Some, like Dunn et al., U.S. Patent No. 4,695,472, sugge~t electrically stressing food by the u~e o~ hlgh ene,rgy, high current density ~le,ctric~l pulses and therea~ter, maintaining the electric~lly ,stressed ~ood under substantially sterile t condition,s and packaging 80 as to have an extended ~helr li~e. Preferably, the electrically stressed ~oodstu~fs are maintained and packaged under aseptic conditions, Dunn et o,l. suggest that the ~helf life tho resulting roodsturf can be improved by ad~usting the, temperature at which the foodstuff i8 treated. Further improvement in shelf life may be obtained by cooling the electric field treated liquid 2~1939 foodstuff to a refrigeration temperature of less than 50 F. Dunn et al. also illustrate that when liquid egg is heated to 58~C (below the temperature neces~ary for thermal pa~teurization of liquid whole egg according to the U.S.D.A.), by use of specific electrical pulses followed by storage at 50F, an increase in refrigerated shelf life is observed.
However, if the treated liquid egg is stored at below 40-F, the refrigerated shelf life of the egg extends to 28 days or longer.
Others, however, suggest adding various agents to the liquid egg to improve refrigerated shelf life. For example, bacteriocin, nisin, and other antibiotic-like preservatives have been suggested for use in connection with pasteurizing liquid egg so as to provide an extended rerrigerated shelf life. For example, as reported in Delves-Broughton et al., ~The use of the bacteriocin, nisin, as a preservative in pasteurized liquid whole eggn, Letters In Applied Mlcroblology, (1992), 15, 133-136, nisin used at levels of 5 mg per liter resulted in a significant increa~e in refrigerated shelf life of pasteurized liquid whole egg. Nisin also protected liquid egg ~rom the growth o~ B~clllus cereus.
or course, the sugge~tion of the addition of nlsin to egg is nothing new. For example, ~lAokburn et ~1., U.S. Patent No. 5,135,910 discusses the application of nisin compositions as a b~cteriocide rOr treating meats, especially poultry, egg~, che~se and rish and for treatment of rood packnging and handling equipment. ~lAckburn et al.
de~cribe that nisin has been applied effectively as a preservative in dairy products such as processed chee~0 and that the use o~ nisin to inhibit the growth Or cortain gram positive bacteria has been well do¢umonted. Bl~ckburn et al. suggest that by the co-administration of nisin and certain chelating or ~urfactant agents, the growth of gram negative . , .
-. ' : : ' : ' - ~219~.9 bacteria such as Salmonella tychimurlum, ~scheria coli and others can be controlled and greater activity towards certain gram positive bacteria such as L~steria monocytogenes can be realized. see also ~l~ckburn et al., U.S. Patent No. 4,980,163 which also suggests the use of ni~in and other bacteriocins in conjunction with food such as eggs.
Despite these technological advances in terms of refrigerated storage and extended refrigerated 6helf life, consideration of the problems as60ciated with thermal abuse resistance as well as methods of overcoming these problems have remained largely unexplored. It i8 known that liquid egg that has been pa~teurized, placed in an extended shelf life container and properly stored at 4C or under will last for elght weeks or longer. In fact, an extended refrigerated shelf life of 12 weeks or more i6 not uncommon. However, it is generally known that as the storage temperature of the liquid egg increases, a decrease in storage life is observed. The inventor has realized that, within limits, for every degree over 40'F that liquid egg is stored, one week of extended re~rigerated shelf life is compromised.
Thu~, lf extended refrigerated shelf life liquid egg ~5 having an antlcipated shel~ e of 12 weeks is re~rlgerated at 50-F instead of 40~F, the resulting egg ~hould have a shelf life of only about 1 to 2 weeks. Thus, a mere 10- change in temperature e~entially negates the entire advantage imparted by v~riou~ extended shelf life pasteurization and packnglng technlque6. As storage temperatures climb abovo 50-F, the resulting shelf life of the liquid egg iB reduced even further to merely a matter of days.
The present inventor has observed that when 3S properly rerrigerated and stored, extended refrigerated shelf life egg eventually goe~ bad and/or when spoilage is brought about by improper filling or contamination during filling, the resulting egg has a ... ~ ~ ,, . , . - . I . , ,." "-" . ;.. , , . . .. , ,.,- ~ .. . , , : , ., . . , . " .. ......
2~21~9 -4- ~
dark, almost brownish color. The pH stays approximately the same or, if anything, becomes more basic, and the material smells sour.
In contrast, when egg has been abused by being held at a temperature of above 40F for any length of time and more particularly, over 45~F, the color becomes a bright and uncharacteristically unnatural yellow, the pH generally drops to as low as 5.5 or below and the product thickens and becomes ,~ 10 viscous. Eventually, the material smells rotten. As a result, thermal abuse is a particularly important problem for consumers. While the egg may not smell - bad and may not have thickened or discolored ~u'~iciently to alert the consumer, its pH and 1~ bacterial content have changed such that the egg ~hould not be used. Often consumers find out about this only a~ter the egg has been incorporated into i other products or consumed.
3 The present inventor believes that, Bac~llu6 cereus and Enterococcus faecalis are ~ di~ficult to kill by certain pasteurization ç technique~. When these bacteria remain in liquid egg and the liquid egg i6 properly stored at 40-F or below, they generally remain dormant. In fact, they may not contribute to spoilage ~t all. However, when ~ ~torod at temperature~ above 40F, and more o~ten at j t~smperatures higher than 45F to about 50P, the ¦ growth o~ th~se di~ficult-to-kill bacteria becomes I ~extr~mely rapid. They can then play a proround role ~ 30 in egg spoilage.
i Manirestly, the considerations surrounding I tho problem o~ thermal storage abuse are extremely ¦ dirrerent than tho~e involved in extending the rorriger~ted shelr li~e o~ liquid egg. Moreover, whils, ao be~ore, the attention o~ the industry was ~ocused on providing method~ Or imparting an extended ! re~rigerated shel~ life, that ~ocus has begun to shi~t. Egg processors can control the way in which ~ ;
' ' 2 1 ~ 9 -5- ~
. ~ -, liquid egg is processed and by selecting particular methodologies and by the use of particular tvpes of extended shelf life packaging, can provide the consumer with pasteurized liquid egg having a re~rigerated shelf life of 3 months or more. However, proceesors can only control the quality of the egg so long as the egg remains under their specific control.
once a consumer has purchased the egg, the responsibility for proper handling and refrigerated storage fall upon the consumer. A few days of improper handling, particularly at temperatures approaching room temperature or above, can virtually eliminate all of the extended refrigerated shelf life that technology can provide. Of course, if the egg turns out to have spoiled prematurely, it is the processor who hears about it and who often must make good even though the reason for the premature spoilage resulted from improper handling and refrigeration on the part of the consumer.
The present invention provides a way to assist processors and users alike in ensuring the continued quality of the liquid egg throughout its intended re~rigerated shelf life by providing for varlous methods o~ imparting thermal storage abuse rooi~tance to liquid egg products.
It i8 an object of the present invention to provide liquid egg which i8 resistant to thermal otorage abu~e.
It i8 another ob~ect of the present invontion to provide liquid egg which will maintain a signi~iaAnt portion of ite anticipated extended rofrigorated ehelf life even after prolonged exposures to improper refrigeration conditions or otherwise elevatod temperature~.
3S It is also an ob~ect of the present lnvention to provide a method ~or imparting thermal otorage abu~e resistance to liquid egg.
.j :
// :
In accordance with these and other objects of the present invention, there is provided a method ; of imparting thermal storage abuse resistance to liquid egg including the steps of electroheating the ; 5 liquid egg, holding the electroheated liquid egg for a period of time sufficient to pasteurize the electroheated liquid egg, and adding to the liquid egg at least one antibacterial agent which is effective against gram positive bacteria in an amount which is effective to provide long term abuse resistance to the liquid egg.
As described more fully herein, electroheating and particularly electroheating utilizing high ~requency AC electrical energy has proved to be revolutionary in the pasteurization and processing of liquid egg. By the use of these electroheating techniques, liquid egg can be processed conveniently at both relatively high and relatively low pasteurization temperatures, without electrolysis, wlthout detrimental coagulation and, with a relatively minimal e~fect on the functionality of the resulting egg. Electroheating as described herein provides for an extremely e~icacious kill of the microbes aontained in liquid egg. Moreover, it has been ob~erved that generally well a~ter pasteurization has b~on completed, the mortality rate of microbes ~ contained in the liquid egg actually increases. By I virtue Or th~ extremely e~icacious kill obtained by ~ ol~ctroheatlng as described herein, the relative ,l 30 number of bacteria remaining within liquid egg a~ter tr~Atment i8 small. It has been ~ound that by adding ~ cortaln antibacterial agents such as, for example, ¦ nieln, to the thus pasteurized liquid egg, thermal ¦ storage abueQ reeietance can be instilled.
Without wi~hing to be bound by any parti¢ular theory o~ operation, certain spoilage ba¢teria Ruch as, for example, Bacillus cereus and Enterococcus ~aecalis, may remain in liquid egg after .'~ .,', 2 ~ 2 ~
~7~
pasteurization. If the pasteurized liquid egg is stored at refrigerated temperatures, and in particular, under 40-F, such bacteria are unable to multiply and grow. However, as the temperature of the liquid egg i8 elevated above 40CF, the conditions for growth of these microbes become favorable and their numbers begin to increase. Within limits, as the temperature increases, so too does the rate of growth of these spoilage bacteria. Therefore, if liquid egg i~ improperly handled or stored, the consequences in terms of compromising the expected refrigerated shelf life of the egg can be significant.
It is believed, however, that if a su~iciently efficacious initial kill can be provided, the addition of nisin or other related antibiotic-like compounds can act together to retard the growth of spoilage microorganisms during the time when the liquid egg is exposed to elevated temperatures.
It is also believed that electroheating ~0 provides qualities to the egg which cannot be obtained by other methodologies. Egg treated by electroheating in accordance with the present invention to which bacteriocin~ such as nisin or other antibiotic compounds have been added is therefore believed to provide particularly efficacious protection against thermal stor~ge abuse.
Moreover, because the electroheating techniques in accordance with the pre~ent invention aro w erul to provide extremely ef~icacious klll without detrimental coagulation and without a sacri~ice Or baking ~unctionality, it is po~sible to nchievo the ob~ectives described herein while maintnining a sub~tantially fully functional egg ~imllar in viscosity in baking ~unctionality and in othor propertie~ to egg directly out o~ the shell.
In accordance with another aspect of the present invention, there is also provided a method of ~toring liquid egg so as to render it resistant to -., ., ,, , . . - , " .. ,, . . ,,., , , . ,. ",; , . . .
21.~1 3~
thermal storage abuse which includes the steps of heating liquid egg and holding the liquid egg for a period of time sufficient to provide an initial average total plate count of 50 or less, adding to the liquid egg at least one antibacterial agent which is e~ective against gram positive bacteria in an amount which is effective to provide long term storage abuse resistance to the liquid egg and storing the liquid egg at a temperature above 40F for at least some portion of time, whereby the liquid egg's shelf life i8 not substantially compromised. Liquid egg resulting from these methods is also contemplated.
Fig. 1 is a schematic representation of one con~iguration of an electroheating based pa~teurization system useful in accordance with the present invention.
The term ~liquid egg~ in accordance with the present invention is meant to include not only liquid egg white and liquid egg yolk, but also combinations o~ each in any predetermined or desirable ratio. The term ~liguid eggn also includes liquid egg white, liquid egg yolk, or combinations thereo~ (referred to a~ ~liquid whole egg~) with additives ~uch as salt, sugar, milk, stabilizers, antibiotics, dextrins, cyclod~xtrins, peroxides, acids such as citric acid and ~ood including solid or particulate foodstuffs.
Liquld egg ~rom which cholesterol has been removed is ~lao included.
The term ~electroheating~ in accordance with the pre~ent invention 18 meant to encompa~s a process o~ generating heat in liquid egg by passing a current through the liquid egg. The liquid egg acts as a resi~tor and heat is generated thereby. A
particularly pre~erred technique for eleatroheating 3S rood i~ described in U.S. Patent No. 4,739,140, which i~ lncorporated by reference.
In a more particularly preferred aspect of the prQsent invention, the liquid egg is electroheated ~ . ....
: ~ , , ~ " .................................... . ,:
: . : , . , : , . ' '' ,.: , " ,:
2 ~
-- --9-- : :
~ . .
with the apparatus and methods described in a copending application entitled ~METHO~S AND APPARATUS
- FOR ELECTROHEATING FOOD EMPLOYING CONCENTRIC
ELECTRODESn filed January 22, 1993 having U.S. Serial No. 007,553. The text of this application is ; incorporated by reference as is fully set forth herein.
As used herein, the terms ~pasteurization~, ~pasteurize~ and ~pasteurized~ refer to the killing of sufficient pathogenic microorganisms contained within food and in particular liquid egg so as to render the , food edible without threat of, for example, salmonella infection. ~Pasteurization~ may also be thought of as a treatment which i~ designed to eliminate, for all practical purposes, pathogenic micro-organisms and, in particular, salmonella, and, secondarily, to reduce f the number of spoilage microorganisms present to improve the keeping quality of the food product. At U.S.D.A. minimum time and temperature parameters, pasteurization will generally produce liquid egg which will have a refrigerated shelf life of between about 7 and about 14 days. For liquid whole egg, a minimum temperature of 140'F and minimum holding time of 3.5 minutes i8 required. ~he definition o~
pA~teurlzation, in terms Or attained temperatures and holding times, for other foods is generally provided by government regulation and industry standards. They are thererore readily acceptable.
~Extended rerrigerated shelf li~e~ means that the liquid egg i~ sare to consume for a period of at least 3 week~ arter treatment in accordance with I tho pre~ent invention. This, of course, assumes ¦ proper refrigerated ~torage. Preferably, the term ¦ ~extonded rerrigerated shelr life~ mean~ that the ~ 35 liquid egg i8 sare to con~ume for a period of at ¦ l-a~t 4 week~ after treatment in accordance with the ~ prosent invention and more often 10 to 12 weeks after I treatment, or longer. An extended refrigerated shelf 2~21~9 life can also be imparted to other perishable foods by the practice of the present invention.
~ Electrolysis~ refers to a chemical process which can take one of at least two forms. One form of electrolysis results in the dissolution of the metal Qlectrodes inserted into the food being treated. As ælectrons flow between the pair of electrodes, the metal within the electrodes becomes ionized, thereby releasing electrons. The ions are soluble and dissolve into the food being treated. Another electrolytic problem is caused by the conversion of conductive ionic species within the food being treated to radicals and gases, such as the conversion of a hydrogen ion to hydrogen gas and chlorine ions to chlorine gas. Hydroxide ions can subsequently be converted to water and oxygen. This conversion can adversely impact the flavor and other advantageous qualities of the treated food both as a result of the direct depletion of ions and their conversion to other species and by initiating other reactions within the ~ood such as oxidation.
Coagulation generally involves the denaturation and agglomeration of protein contained in a rood. Some ~oods, like, orange ~uice, do not co~gul~te when heated. Other foods, such as liquid e~g, do coagulate when a su~ficient amount of energy i~ applied.
In accordance with the present invention as it relAtes to liquid egg and other coagulable roods, 30 CoagUlAtlon i8 usually to be minimized. At certain pa~teurlzation temperatures, ~or liquid egg, some ~egree Or coagulation will occur. However, in nccordance with the present invention, and unless the llquid egg is to be cooked, ndetrimental coagulation~
~hould be prevented. Detrimental coagulation is an increa~e in the viscositv o~ the liquid food such that it~ smooth pourable nature is compromised. Its r~t:: - . . . , , , , ' 2~2~
functionality is also compromised at this point and visible particles of egg appear.
The term ~antibacterial agentn in accordance with the present invention includes any antibiotic agent which is effective against gram positive bacteria. More particularly, however, it refers to bacteriocins such as, for example, nisin, epiderman, cinnamycin, duramycin, ancovenin, Pep 5, tylosin, and subtilin. These compounds may, of course, also be ef~ective in controlling some forms of gram negative bacteria. ~ `
The term ~retained baking functionality~
means that despite the application of heat in accordance with the present invention, the liquid egg 15 i8 useful for most commercial and home, if not all, baking applications. Baking functionality relates primarily to the emulsification properties of the liquid egg. This function directly relates to the stability of water/oil, water/air, oil/air, or water/oil/air phaises. Emulsifications influence the viscosity of the batter, volume of the baked goods and stability thereof. The stability of a two or three phAse ~ystem also greatly affects the texture of the resulting baked product. In a cake, a desirable soft uni~orm crumb can be achieved only with the proper emul~i~lc~tlon ~y~tem. In fact, the quality of oort~ln baked goods, such as, for example, sponge c~ke, is considered wholly dependent upon the quality Or the egg used. Good egg product, that is one having hlgh baking ~unctionality, yields high volume and so~t texture.
~ Thermal abuse~ in the context of the pre~ent invention involves the exposure of liquid egg which i~ intended to be stored under refrigerated condition to temperature3 Or over 40F and, in particular, 50-F or over rOr a time which is ~u~ficient ror the liquid eggs' temperature to begin to rise. Thermal abuse can occur in many forms, such 2~2~
a~ when a refrigeration unit is inadequate to provide proper refrigerated storage. For example, in convenience stores, refrigeration space is usually at a premium. Often, because of the relatively high turnover, products which should be refrigerated are kept in a cold room adjacent actual refrigerated storage units. In supermarkets, eggs and other dairy products are traditionally sold in open refrigerated racks or cases. The temperature of the material contained within packages in these cases can depend on the ambient temperature of the store, the proximity of the package to the front of the rack and whether or not the package is in direct contact with a refrigerated shelf or is merely stacked upon other containers.
Thermal abuse may also occur, or may be compounded, when a consumer removes a poorly refrigerated package from such an open refrigerated case and places the refrigerated product in a shopping cart early in an extensive shopping trip. The refrigerated product may therefore be exposed to a~bient temperature conditions for up to several hours untll the package is taken home and placed into a refrigRrator.
Thermal abuse can also occur during normal 6hipping and handling. For example, the refrigeration unlt on a re~rigerated truck or boxcar can break duxing tran~it, thereby expo~ing the paakages and thoir content~ to elevated temperatures for a prolonged period o~ time. In addition, during the shipplng process, containers may wait on a loading dock ~or several hours either prior to being loaded onto a truck or thereafter. -In accordance with the present invention, ~thermal abuse re~i~tance~ can be imparted to liquid egg. In the broadest sense, ~thermal abuse reeistance~ in accordance with the present invention mean~ that liquid egg processed in accordance with the .
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present invention which has been thermally abused will retain a substantially greater portion of its intended re~rigerated shelf life than would liquid egg which has been merely pasteurized under identical conditions and thermally abused to the same extent. For example, egg pasteurized and packaged under identical conditions and exposed to the same degree of thermal abuse, will last longer. Preferably, liquid egg so treated in accordance with the present invention will have at least one day's longer shelf life. Of course, the lesser the degree of thermal abuse, i.e. exposure to lower temperatures for shorter periods of time, the less severe the impact of the exposure. Therefore, by the practlce of the present invention, it may be possible to negate entirely the effects of such minimal abuse and/or allow the liquid egg to retain a much larger percentage of its extended refrigerated shelf life. Thus, for example, liquid egg stored at 45-F which might be expected to have its re~rigerated shel~ life reduced ~rom 12 weeks to 7 weeks, might last for 8 weeks or longer. In addition, the use of electroheating and, ~or example, nisin, in accordance with the present invention, allows the processor to realize not only a low total plate count 25 ~nd thermal abuse resistance, but also a higher level o~ retained baking functionality with little or no detrimental coagulation. This is especially true when the liquid egg o~ the present invention is compared to egg proce~sed by other methods to yield thc same plate count.
The method~ o~ the present invention will be better understood with re~erence to the schematic diagram o~ Fig. 1, which de6cribes a typical device used ~or pasteurizing liquid egg products. Thi~
typlcal egg pa~teurizer has, however, been modi~ied by substitution o~ an electroheater 7' where a plate heat exchanger or other conventional heating device could be used. This and similar devices can also be used in .~ . , . . , . ~ , , 2 ~ 2 ~
connection with the heat treatment of a wide variety of foods.
As shown in Fig. 1, and for illustrative purpose~ only, liquid whole egg, usually in 5 refrigerated form, i8 transferred from a holding tank 1 to a balance tank 2. Liquid egg could also be introduced into the apparatus directly from a tank car, tank truck or from an egg breaking line.
~, Thereafter, the liquid whole egg is pumped through a timing pump 3 which keeps the liquid whole egg moving throughout the entire pasteurization apparatus. The liquid whole egg is then preferably preheated by any conventional means of heatiny such as ovens, vats and/or ~team infusion systems. In addition, electroheating elements or cells of the present invention can also be used to preheat the liquid whole egg. The liquid whole egg is usually brought from re~rigerated or room temperature up to about 139F or higher. More preferably, however, a conventional plate heat exchanger 4 is used to accomplish p preheating.
As shown in Fig. 1, the regeneration y; ~oction 5 of a conventional plate heat exchanger 4 is connect-d to the output o~ timing pump 3. The liquid 2g whole egg temperature is rai~ed in the regeneration ~-ction 5 ~rom, for example, 35~-40F to between elbout 90-F and about 120-F. Thereafter, the liquid whole egg 1~ introduced into the heating section 6 of plate heat exchanger 4 ~or further preheatlng. In heating ~oction 6 the temperature of the liquid whole egg i8 ~urther elevated in temperature to something below pasteurization temperature, usually between about 120-F and about 149-F. In a pre~erred mbodiment, preheatlng temperatures o~ about 123-F and about 149-F and more pre~erably between about 130-F
and about 144-F are used ~or liquid whole egg. Unless relatively high pasteurization temperatures are used, it is generally preferable that the maximum preheating .' 2~ 2~9~.9 temperature be selected such that it is below the pasteurization temperature of the particular form of ~ood being treated. In the context of liquid whole eqg, preheating temperatures generally range up to about 139-F.
Thereafter, the liquid whole egg passes between the electrodes of an electroheater 7~. The electroheater 7' is supplied with a high frequency AC
electric current which is effective to heat the liquid whole egg without electrolysis. Preferably, the AC
electric current has a frequency above about loo Hz and, more preferably, above about loo kHz. Most preferably, freguency used ranges from between about 150 kHz and about 450 kHz. This energy is appl$ed to the liquid whole egg in such a way so as to avoid detrimental coagulation. In electroheater 7' the temperature of the liquid whole egg is elevated from its preheated temperature to the desired pasteurizing temperature. Pasteurization temperatures in excess of 170-F for liquid whole egg can be achieved, however, preferred pasteurization temperatures o~ between about 140F and about 16~F
and more preferably, between about 140~F and about 155-F are achieved. Most preferably, pasteurization temperatures between about 140F and about 145'F ~re used. These temperatures are, of course, ~or liquid whole egg only. For liquid egg white, temperatures should range from between about 124^F (with peroxide) or about 134'F (without peroxide) to about 139-F.
~ ter being electroheated, the liquid whole egg i~ then passed through holding tubes 8 where it is held ~or a period o~ time sufficient to complete pa~teurization in accordance with the Federal Regulation~. Generally, holding times o~ between nbout 0.1 ~econds and about 5 minutes can be used, however, times of between about 2 and about 4 minutes are pre~erred. The liquid whole egg then passes to ~121 Q~9 flow diversion valve 9. If the temperature of the liquid whole egg exiting holding tubes 8 is below a preset value the liquid whole egg is returned to the balance tank 2 to go through another pasteurization pas~. If, however, the exit temperature is at or above the preset value, the liquid whole egg is allowed to proceed via the cooling means 10 to the packager 11, or to a holding tank, tank car, etc.
When cooled by cooling means 10, the pasteurized electroheated liquid whole egg preferably returns to a refrigerated temperature of between about 32F
and 45-F.
Cooling means 10 can be any device useful for lowering the temperature of the electroheated liquid egg, liquid whole egg in this case, quickly enough to avoid detrimental coagulation. When high temperatures, and in particular, temperatures over about 155-F to 160-F and higher are reached during pasteurization, the need to rapidly cool the liquid whole egg become~ acute. In such cases it may be necessary to utilize a nY~-shaped cooling device such as described in the aforementioned U.S. Patent Applicatio-n No. 07/862,198, filed on April 2, 1992.
When, however, pasteurization temperatures are below 160-F and more particularly below 155~F, it i~ ~¢ceptable to use more conventional cooling mean~ 10' ~uch as the cooling/regeneration section and re~rigeration section of a conventional plate heat exchanger. In ~act, coollng means 10' may be the coollng/regeneration and re~rigeration section~ 14 and 16 refipectlvely, o~ plate heat exchanger 4, as ~hown in dashed lines in Fig. 1. In that case, after leaving rlow diversion valve 9, the electroheated liquid whole egg would flow into the cooling/regeneration ~ection 14 o~ plate heat exchanger 4 via conduit or pipe 12 where its temperature would be lowered to between about 120-F
and about 60-F. Therea~ter, the cooled liquid whole : . :
2~ .9 egg would be refrigerated in the refrigeration section 16 of heat exchanger 4 where its temperature would be lowered to between about 32F and about 45F
and, more preferably, between about 32F and about 40-F. Thereafter, the refrigerated liquid whole ; egg could be stored, loaded into a tank car or truck or packaged in packaging device or packager 11.
Packaging device 11 need not be aseptic. By ; electroheating and storage at 40F or under, it is not ; 10 nece~sary to aseptically package processed pasteurized liquid egg in order to obtain an extended refrigerated shel~ life and, more particularly, an extended re~rigerated shelf life of eight weeks or more.
Aseptic packaging procedures are described in 21 C.F.R. 113.3, 114.40(g) and 113.100(a)(4).
Generally during aseptic processing, a commercially sterilized product is introduced into a sterile package under sterile conditions such that the filling and sealing of the package is all conducted in a sterile environment. Of course, liquid egg in ! accordance with the present invention and the ma~orlty known technology i8 not sterile. Nonethele6s, a~eptic packaging procedures insure that a tatistlcally lnsigni~icant number of cells are ~5 lntroduced during packaging. For purposes of lllustration only, aseptic packaging should introduce i approximately one cell per 1,000,000 packages.
Asoptic packaging can be accomplished using an International Paper Model SA aseptic packager or a 8cholle Model 10-2E aseptic packager. Of course, ~eeptic packaging may be utilized in accordance with the present invention. However, because of the present invention, it need not be.
Another type o~ packaging userul in accordance with the present invention is the so-called ~clean pack~ which may be produced using a Cherry-Burrell packager Model EQ3 or EQ4. This type of packaging has a higher failure rate or, more correctly 2 1 2 ~
put, a higher incidence of the introduction of microorganisms during packaging than a truly aseptic system. For illustration purposes only, a clean pack may introduce one cell per every 100,000 packages.
S While the u~e o~ this packaging technology does not qualify as a~eptic, it is certainly acceptable in terms of the present invention and such devices may be used as packaging device 11. These Cherry-Burrell packages can also be run so as to produce plain ~anitized clean containers as discussed below. For example, if the packages are not treated with a peroxide spray prior to filling, they can be considered sanitized, but not aseptic or ~clean packs.~ These are both forms of extended refrigerated shelf li~e packages.
Also useful in accordance with the present invention are plain sanitized clean containers produced and sanitized using ~good manufacturing procedures~ in accordance with all government regulations. Such containers which have been properly sanitized may introduce as many as, for illustration purposes only, one cell per hundred packages. Because of the superior kill provided by electroheating and the growth inhibitory effect of proper re~rigerated storage, ~uch an addltion o~ cells is not considered ignl~lci~nt.
~ he~e aforementioned packages, which are all ~pecifically useful in practicing the present invention to provide extended shelf life, may be contra~ted with a ~dirty package~ which has not been ~anitlzed nor packaged under clean or aseptic conditions. Such containQrs may introduce 1,000 cells per package or more which is statistically signi~icant relativ~ to the number Or cells remaining in pa~teurized liquid egg after succes~ful pa~teurization. Any other type Or package can be utilized, as individual customers may require. Of course, the introduction of any microorganisms after 7` ~ , . .
2121~
treatment is to be avoided at all costs. However, the packaging processes described herein do not significantly increase the total plate count and, therefore, should not affect refrigerated shelf life.
With this overview in mind, the various aspects of the ; present invention will now be described.
In accordance with the present invention, sufficient antibacterial agent is added to the liquid egg so as to provide long term thermal abuse resistance thereto. If, for example, nisin is added prior to pasteurization, there is some evidence that it will also assist in providing a more efficacious pasteurization~ However, the amount of nisin remaining within the resulting liquid egg may be reduced, thereby compromising the degree of thermal abuse resistance which may be imparted. Therefore, it may be advantageous to add nisin or other antibacterial agents in accordance with the present invention to the liquid egg after pa~teurization.
However, it i8 also possible to pasteurize liquid egg using, for example, nisin and then augment the nisin content o~ the egg after pasteurization.
The amount of antibacterial agent useful in acaor~ance with the pre~ent invention can vary widely depending upon the extent of the initial kill of mlcrobes provided by pasteurization, the relative chance o~ thermal storage abuse, the degree and extent o~ anticipated thermal storage abuse, the particular antibacterial agent or agents u~ed and the anticipated extended refrigerated shelf life of the resulting liquid egg. For nisin, an amount of at least about 0.75 mg/kg of liquid whole egg should be used. More pr-rerably, between about 1.25 mg/kg and about 250 ~g/kg o~ ni~in may be used. The amounts of other ~ntlbncterial agents can be ad~usted so as to provide a level of efficacy substantially corresponding to the u~eful levels of nisin.
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The efficacy of the addition of such antibacterial agents may be enhanced by the addition of a chelating agent or a surfactant agent as described in U.S. Patent No. 5,135,910, the text of which i8 incorporated by reference. Chelating agents used in accordance with the present invention may include EDTA, CaEDTA, CaNa2EDTA, and other alkyldiamine tetraacetates, EGTA, citric acid, and citrate. Surfactants as described herein may include lo tweeng, tritons, glycerides, fatty acids, quaternary compounds, sodium dodecyl sulphate and cocamido propyl betaine. These can be present in an amount of between about 0.1 mM to 20 mM.
In addition, it i8 also known that compounds auch as nisin can be used in combination with glycanohydrolases to provide particularly efficacious kill~ during pasteurization. It is believed that the coaction of these various agents, such as lysozyme, will also be efficacious in providing enhanced thermal abuse resistance. Lysozyme, for example, may be added in an amount of between 0.1% and about 1.0% by weight.
These additional ingredients may be added bofore, during or after pasteurization. They may be ~dded with the antibacterial agent or separately. I~
2S Added b~rore pa~teurization, it may also be desirable to aug~ent these materials as they may be digested durlng hoating.
Consistent with the belief that the combination of a particularly ef~icacious kill and the u~o o~ ~n antibiotic agent such a~, for example, ni~in, can provide significant thermal abuse rQ~i~tanoe during storage, a preferred aspQCt of the pro~ent invention involves electroheating the liquid egg a~ previou~ly described ~uch that the total initial plate count of the liquid egg is under about 50. Howevor, the liquid egg mu~t be treated in ~u¢h a way that its baking functionality is ~ub~tantially retained and the detrimental coagulation :: ' , ,.. ', ". ,.' .,;,, ' ,,'., , . ' ' ,, . , :, ' ' .
2~2~
attendant certain pasteurization processes is minimized. Thus higher temperature techniques such as tho~e disclosed in Jones et al., U.S. Patent No. 3,113,872, and Sw~rtzel et ~1 ., U . S . Patent No. 4,808,425, are generally contraindicated. Of course, 6uch techniques may be useful in accordance with the present invention. However, they are believed to be unable to provide the extremely efficacioug kill with little or no sacrifice in terms of detrimental coagulation and baking functionality as called for in this aspect of the present invention.
In accordance with this preferred aspect of the present invention, liquid egg is electroheated, with or without the addition of nisin, to a temperature of between about 140F and about 145F and is held at that temperature for approximately 3.5 minutes. Thereafter, nisin or other similar agents may be added and the product is packaged and stored under refrigerated conditions. Preferably, a storage temperature of 40-F or below is maintained. If the resulting package liquid egg is stored improperly for any length o~ time, the combination of the partlcularly low kill and the antibacterial agent such as nlsin should provide significant protection against epoilage.
The foregoing will be better understood with rererence to the following examples. The6e examples ar- for purposes o~ illustration. They are not to be con~idered limiting as to the scope and nature o~ the pre~ent lnvention.
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Six two pound gable top containers containing liquid whole egg electroheated to a t~mperature o~ 147-F and held at that temperature ~or approximately 3 1/2 minute~ were removed from a processing run. The liquid egg was packaged using a Cherry-Burrell model EQ3 packager which provides for a so-called ~clean pack~. The liquid whole egg included 1: , , ,. , ;, , .
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2~ 2~ 989 citric acid in an amount which was insufficient to provide any preservative effect but was useful for stabilizing the color of the egg yolk. The treated liquid egg has an approved ten week refrigerated shelf life. 200 milligrams of NISAPLIN, available from Barrett Ltd. Trowbridge, Wilts, England BA148TR, in ~olution was injected through the container using a sterile syringe. One milligram of NISAPLIN contains about 0.026 milligrams of nisin, i.e., NISAPLIN is about 1/40th nisin by weight. Thereafter, the introduction hole was taped shut. Four of the six container6 were treated in this way. The remaining two containers were used as a control. Each of these were punctured with a sterile syringe and thereafter were taped shut. The six containers were then stored in a windowless room at an ambient temperature which ranged from between about 68~F and about 75'F.
Four days after treatment both of the controls had turned 60ur. They were characterized by strong smell, high viscosity, and uncharacteristically bright yellow color. The plate counts were too high to mea~ure. The liquid egg in two of the four test containers had begun to show some signs of thickening.
Tho plat~ counts for these two samples were also too j 25 high to measure. However, they did not have an ob~ectlonable smell. ~y standard observation, it was believed that the~e containers included egg which was 8a~e ~or consumption at that moment. However, there WAO at least a 50% chance that khe egg would become lnedlble within 24 to 48 hours.
The remaining two samples of egg treated in accordAncQ wlth the present invention showed no signs of thlckenlng, discoloration or other physical change.
The egg contained in these second two containers did not include an ob~ectionable smell and tasted fresh and sweet. Total plate counts of 500 and 600 were ,, observed.
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- . -23-The electroheated liquid egg in accordance with Example 1, when stored at room temperature between 2 and 3 days, turned sour and spoiled.
However, by the use of nisin in accordance with the present invention, the liquid egg was still safe to consume and palatable for 4 to 5 days or longer. This represents almost a 100% increase in the shelf life of the liquid egg even over egg which had been electroheated. Liqjuid egg treated by conventional plate heat exchangers, for example, at 147F or so would be unlikely to last for more than 1 to 2 days be~ore 8poiling. Thus the practice of the present invention including both electroheating to provide a particularly e~icacious kill in combination with an antibacterial agent such as nisin can provide a significant increase in storage stability over conventionally pasteurized egg.
This rather rigorous test exemplifies the advantages of the present invention when liquid egg is stored on a countertop at room temperature. Of course, if liquid egg was merely stored under improper re~rigeration conditions such as, at between about 45-F and 50'F, the extended refrigerated shelf ~ o~ the liquid egg would not be reduced to only 5 or ~ore day6. Under such conditions, particularly if the lmproper storage does not periist, the extended re~rigerated ~helf life of the egg may be ~ignificantly retained 80 that the liquid egg may be ~tored ~or as much as 6 to 8 weeks or more.
~m~
The six containers described in Example l were re~ealed and held at room temperature for four additional days. When the two control containers were opened, a ~trongly rotten odor was given off. Visible 3S colonies o~ bacteria were present in the egg and the gg had noticeably thickened and darkened in aolor.
The four cartons containing electroheated liquid whole egg and nisin had also become thick and turned Aour.
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The pH of all six containers was about 5.3. In addition, while a sour fermentative odor was detected, the rotten odor normally associated with egg turning bad was not noticeable.
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Six additional containers of liquid egg as described in Example 1 were prepared and stored. 300 mg of NISAPLIN was introduced into two containers, 400 mg of NISAPLIN was introduced into two containers and 500 mg of NISAPLIN was introduced into the last two containers. The four containers including 300 and 400 mg of NISAPLIN were observed to be thick, their color had changed, and a sour odor was present.
The pH of the samples was about 5.45. The two containers including 500 mg of NISAPLIN, however, were per~ect in terms o~ color and viscosity. Their smell was sweet and their viscosity was about 6.75. The six containers were stored for eight days at room temperature of between about 68F and about 75F.
x~mpl~ ~
Ten thousand pounds of TABLE READY brand liquid whole egg from Papetti'6 Hygrade Egg Products, Inc. o~ Elizabeth, New Jersey were pasteurized by electroheating at a temperature of approximately 143-F
2S and held at that temperature for approximately three ~nd a hal~ minutes. The liquid egg was packaged using a Cherry-~urrell Model EQ3 Packager which provides for ~o-called ~Clean Pack~n. Three pounds of NISAPLIN was dis~olved in forty pounds of water and introduced into the liquid whole egg whlle the egg was in the holding tank prior to pasteurization. A~ter processing the containere, including liquid whole egg pasteurized in the pre~ence o~ nisin, were stored at either 40-F
or 50-F, both of which can broadly be considered ~rerrlgerated~ temperatures. Controls consisting of TABLE READY liquid whole egg were processed and packaged under the same conditions as described herein, without the addition of NISAPLIN. The - .. -. - . . .. .. ., : . . .. .
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controls were actually processed a day before the NISAPLIN containing samples. The amount of NISAPLIN
used equated to approximately 7.8 mg. per ounce or 27.5 mg. per hundred grams of liquid whole egg.
The amount of nisin thereby delivered was approximately 0.20 mg. per ounce or approximately 0.68 mg. per hundred grams. The results are reported in Table I.
TABLE I -~
~Ni~in wa~ ~dd-d b~rOre pal~t~urization) ~)UIPLE O _ ~ _ l~vl~ s 6 V _ 10 IIUI~L~10 60 L'r ~00 ~C0 L'r 10: = 11)0 L~ 00 L~ 100 100 Dr 100 LT 100 colmoL lo LT 100 LT 100 LT 100 LT 100 LT 100 L7,' 100 LT 100 ll,50o 150,000 TN~C
__ _ _ _ g~FLE 10 LT 100 20 L'r 100 LT 100 LT 100 LT 100 LT 100 8,900 TNTC TNTC
CO~XL _ L'r 1-0 L'r lOD ~C _ TNTC TNTC TNTC TNTC TNTC TNTC
L~V~LS U~ED NI~PLIN 7 8 ~g /02 . LT- L--~ Tllan 27 5 ~9/100 g TNTC - Too Nu~lrou- to Coune NI8IN 0 20 ~g/oz 0 68 ~19/lOO 9 At 40-F, the controls exhibited a ~igni~icant increase in total plate count between the 25 ~eventh and eighth week. By the ninth week, the ~ample~ opened were no longer consumable. In contra~t, the sample containing NISAPLIN continued to have acceptable total plate counts for a ~ull ten wo~ks .
The llguld egg stored at 50~F, without NISAPLIN, lasted approximately two weeks before the tot~l plate count increased to the point where the number o~ bacterla were too numerous to count. In contrsat, liquid egg processed according to the 3S preaent lnvention, including NISAPLIN, did not exhibit a signi~icant increase in total plate count until Week 8 at which point, the liquid egg was still con~umable.
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This test underscores not only the importance of the discovery of the present invention, but al80 the unexpected nature of that discovery. As prevlously de~cribed, it has been reported that nisin used at levels of 5 mg. per liter resulted in an increase in refrigerated shelf life of pasteurized liquid whole egg. Indeed, as exemplified by the samples stored at 40, the use of nisin, particularly in combination with electroheating, can provide an enhanced and extended refrigerated shelf life. Of course, it should be noted that without the use of electroheating (as was the case in the reported literature), the shelf life of the pasteurized liquid egg, both with and without nisin was considerably shorter than exemplified herein. However, when stored at 50-F, a significant and unexpected difference in the keeping qualities of the liquid egg was observed.
Electroheated liquid egg having an extended refrigerated shelf life by virtue of the electroheating process alone spoiled in under three weeks. If properly stored, electroheated liquid egg would be expected to have an extended refrigerated shel~ e o~ 8-10 weeks. With the addition of nisin, however, the llquid whole egg retained most of the predicted shelf life lastiny between eight and nine week~ prior to epoilage. Such a profound difference in abuse re~lstance could not have been predicted based upon the e~ects of nisin on extending re~rigerated ~hel~ life.
~ L~
Liquid egg was processed and prepared as de~cribed in Example 1 with 7.8 mg. per ounce of NISAPLIN being in~ected into the already processed egg ~eal-d within a container using a sterile syringe.
3S The resulting containers were stored at 50F and te~ted as previously described. Initial testing of the liquid egg exhibited a total plate count of 10. A
~econd container was opened at the end of Week 1, and 2 t ~ 9 -27- ~
:
the total plate count again was less than 10. A third container was opened at the end of the second week, and the total plate count was 30. A fourth container WA8 opened at the end of three weeks, and the total plate count was less than lo. After four weeks, another sample was tested, and the total plate count was 360. Samples were also tested at Weeks 5, 6, 7, 8, 9 and lo. However, in each case, the total plate count was too numerous to count. This shows that particularly unexpected results are obtainable by the use of nisin, prior to pasteurization, in combination with electroheating.
~x~m~10 6 Additional containers of TABLE READY brand li~uid whole egg were prepared as described in Examples 1 and 5. However, into each, NISAP~IN in the amount of 15.6 mg. per ounce or 55.0 mg. per hundred grams was injected. The initial total plate count was 10. The plate count after one week was 10. After the second and third weeks, the total plate count was less than 10. A~ter four weeks, the total plate count wa~ 10. Individual samples checked in Wee~s 5 and 6, however, had plate counts that were too numerous to count. These last two examples illustrate that nisin 2S i~ u~e~ul, both be~ore and after pasteurization, and at levels quite unexpected over the art.
The principles, preferred embodiments, and mode~ of operation Or the pre~ent invention have been d~aribsd ln the foregoing specirication. The invontlon which iG intended to be protected herein, however, is not to be construed as limited to the particular embodiments disclosed, since these are to be regarded illustrative rather than restrictive.
Varlation~ and changes may be made by others without departlng from the spirit and scope of the invention.
As described more fully herein, electroheating and particularly electroheating utilizing high ~requency AC electrical energy has proved to be revolutionary in the pasteurization and processing of liquid egg. By the use of these electroheating techniques, liquid egg can be processed conveniently at both relatively high and relatively low pasteurization temperatures, without electrolysis, wlthout detrimental coagulation and, with a relatively minimal e~fect on the functionality of the resulting egg. Electroheating as described herein provides for an extremely e~icacious kill of the microbes aontained in liquid egg. Moreover, it has been ob~erved that generally well a~ter pasteurization has b~on completed, the mortality rate of microbes ~ contained in the liquid egg actually increases. By I virtue Or th~ extremely e~icacious kill obtained by ~ ol~ctroheatlng as described herein, the relative ,l 30 number of bacteria remaining within liquid egg a~ter tr~Atment i8 small. It has been ~ound that by adding ~ cortaln antibacterial agents such as, for example, ¦ nieln, to the thus pasteurized liquid egg, thermal ¦ storage abueQ reeietance can be instilled.
Without wi~hing to be bound by any parti¢ular theory o~ operation, certain spoilage ba¢teria Ruch as, for example, Bacillus cereus and Enterococcus ~aecalis, may remain in liquid egg after .'~ .,', 2 ~ 2 ~
~7~
pasteurization. If the pasteurized liquid egg is stored at refrigerated temperatures, and in particular, under 40-F, such bacteria are unable to multiply and grow. However, as the temperature of the liquid egg i8 elevated above 40CF, the conditions for growth of these microbes become favorable and their numbers begin to increase. Within limits, as the temperature increases, so too does the rate of growth of these spoilage bacteria. Therefore, if liquid egg i~ improperly handled or stored, the consequences in terms of compromising the expected refrigerated shelf life of the egg can be significant.
It is believed, however, that if a su~iciently efficacious initial kill can be provided, the addition of nisin or other related antibiotic-like compounds can act together to retard the growth of spoilage microorganisms during the time when the liquid egg is exposed to elevated temperatures.
It is also believed that electroheating ~0 provides qualities to the egg which cannot be obtained by other methodologies. Egg treated by electroheating in accordance with the present invention to which bacteriocin~ such as nisin or other antibiotic compounds have been added is therefore believed to provide particularly efficacious protection against thermal stor~ge abuse.
Moreover, because the electroheating techniques in accordance with the pre~ent invention aro w erul to provide extremely ef~icacious klll without detrimental coagulation and without a sacri~ice Or baking ~unctionality, it is po~sible to nchievo the ob~ectives described herein while maintnining a sub~tantially fully functional egg ~imllar in viscosity in baking ~unctionality and in othor propertie~ to egg directly out o~ the shell.
In accordance with another aspect of the present invention, there is also provided a method of ~toring liquid egg so as to render it resistant to -., ., ,, , . . - , " .. ,, . . ,,., , , . ,. ",; , . . .
21.~1 3~
thermal storage abuse which includes the steps of heating liquid egg and holding the liquid egg for a period of time sufficient to provide an initial average total plate count of 50 or less, adding to the liquid egg at least one antibacterial agent which is e~ective against gram positive bacteria in an amount which is effective to provide long term storage abuse resistance to the liquid egg and storing the liquid egg at a temperature above 40F for at least some portion of time, whereby the liquid egg's shelf life i8 not substantially compromised. Liquid egg resulting from these methods is also contemplated.
Fig. 1 is a schematic representation of one con~iguration of an electroheating based pa~teurization system useful in accordance with the present invention.
The term ~liquid egg~ in accordance with the present invention is meant to include not only liquid egg white and liquid egg yolk, but also combinations o~ each in any predetermined or desirable ratio. The term ~liguid eggn also includes liquid egg white, liquid egg yolk, or combinations thereo~ (referred to a~ ~liquid whole egg~) with additives ~uch as salt, sugar, milk, stabilizers, antibiotics, dextrins, cyclod~xtrins, peroxides, acids such as citric acid and ~ood including solid or particulate foodstuffs.
Liquld egg ~rom which cholesterol has been removed is ~lao included.
The term ~electroheating~ in accordance with the pre~ent invention 18 meant to encompa~s a process o~ generating heat in liquid egg by passing a current through the liquid egg. The liquid egg acts as a resi~tor and heat is generated thereby. A
particularly pre~erred technique for eleatroheating 3S rood i~ described in U.S. Patent No. 4,739,140, which i~ lncorporated by reference.
In a more particularly preferred aspect of the prQsent invention, the liquid egg is electroheated ~ . ....
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with the apparatus and methods described in a copending application entitled ~METHO~S AND APPARATUS
- FOR ELECTROHEATING FOOD EMPLOYING CONCENTRIC
ELECTRODESn filed January 22, 1993 having U.S. Serial No. 007,553. The text of this application is ; incorporated by reference as is fully set forth herein.
As used herein, the terms ~pasteurization~, ~pasteurize~ and ~pasteurized~ refer to the killing of sufficient pathogenic microorganisms contained within food and in particular liquid egg so as to render the , food edible without threat of, for example, salmonella infection. ~Pasteurization~ may also be thought of as a treatment which i~ designed to eliminate, for all practical purposes, pathogenic micro-organisms and, in particular, salmonella, and, secondarily, to reduce f the number of spoilage microorganisms present to improve the keeping quality of the food product. At U.S.D.A. minimum time and temperature parameters, pasteurization will generally produce liquid egg which will have a refrigerated shelf life of between about 7 and about 14 days. For liquid whole egg, a minimum temperature of 140'F and minimum holding time of 3.5 minutes i8 required. ~he definition o~
pA~teurlzation, in terms Or attained temperatures and holding times, for other foods is generally provided by government regulation and industry standards. They are thererore readily acceptable.
~Extended rerrigerated shelf li~e~ means that the liquid egg i~ sare to consume for a period of at least 3 week~ arter treatment in accordance with I tho pre~ent invention. This, of course, assumes ¦ proper refrigerated ~torage. Preferably, the term ¦ ~extonded rerrigerated shelr life~ mean~ that the ~ 35 liquid egg i8 sare to con~ume for a period of at ¦ l-a~t 4 week~ after treatment in accordance with the ~ prosent invention and more often 10 to 12 weeks after I treatment, or longer. An extended refrigerated shelf 2~21~9 life can also be imparted to other perishable foods by the practice of the present invention.
~ Electrolysis~ refers to a chemical process which can take one of at least two forms. One form of electrolysis results in the dissolution of the metal Qlectrodes inserted into the food being treated. As ælectrons flow between the pair of electrodes, the metal within the electrodes becomes ionized, thereby releasing electrons. The ions are soluble and dissolve into the food being treated. Another electrolytic problem is caused by the conversion of conductive ionic species within the food being treated to radicals and gases, such as the conversion of a hydrogen ion to hydrogen gas and chlorine ions to chlorine gas. Hydroxide ions can subsequently be converted to water and oxygen. This conversion can adversely impact the flavor and other advantageous qualities of the treated food both as a result of the direct depletion of ions and their conversion to other species and by initiating other reactions within the ~ood such as oxidation.
Coagulation generally involves the denaturation and agglomeration of protein contained in a rood. Some ~oods, like, orange ~uice, do not co~gul~te when heated. Other foods, such as liquid e~g, do coagulate when a su~ficient amount of energy i~ applied.
In accordance with the present invention as it relAtes to liquid egg and other coagulable roods, 30 CoagUlAtlon i8 usually to be minimized. At certain pa~teurlzation temperatures, ~or liquid egg, some ~egree Or coagulation will occur. However, in nccordance with the present invention, and unless the llquid egg is to be cooked, ndetrimental coagulation~
~hould be prevented. Detrimental coagulation is an increa~e in the viscositv o~ the liquid food such that it~ smooth pourable nature is compromised. Its r~t:: - . . . , , , , ' 2~2~
functionality is also compromised at this point and visible particles of egg appear.
The term ~antibacterial agentn in accordance with the present invention includes any antibiotic agent which is effective against gram positive bacteria. More particularly, however, it refers to bacteriocins such as, for example, nisin, epiderman, cinnamycin, duramycin, ancovenin, Pep 5, tylosin, and subtilin. These compounds may, of course, also be ef~ective in controlling some forms of gram negative bacteria. ~ `
The term ~retained baking functionality~
means that despite the application of heat in accordance with the present invention, the liquid egg 15 i8 useful for most commercial and home, if not all, baking applications. Baking functionality relates primarily to the emulsification properties of the liquid egg. This function directly relates to the stability of water/oil, water/air, oil/air, or water/oil/air phaises. Emulsifications influence the viscosity of the batter, volume of the baked goods and stability thereof. The stability of a two or three phAse ~ystem also greatly affects the texture of the resulting baked product. In a cake, a desirable soft uni~orm crumb can be achieved only with the proper emul~i~lc~tlon ~y~tem. In fact, the quality of oort~ln baked goods, such as, for example, sponge c~ke, is considered wholly dependent upon the quality Or the egg used. Good egg product, that is one having hlgh baking ~unctionality, yields high volume and so~t texture.
~ Thermal abuse~ in the context of the pre~ent invention involves the exposure of liquid egg which i~ intended to be stored under refrigerated condition to temperature3 Or over 40F and, in particular, 50-F or over rOr a time which is ~u~ficient ror the liquid eggs' temperature to begin to rise. Thermal abuse can occur in many forms, such 2~2~
a~ when a refrigeration unit is inadequate to provide proper refrigerated storage. For example, in convenience stores, refrigeration space is usually at a premium. Often, because of the relatively high turnover, products which should be refrigerated are kept in a cold room adjacent actual refrigerated storage units. In supermarkets, eggs and other dairy products are traditionally sold in open refrigerated racks or cases. The temperature of the material contained within packages in these cases can depend on the ambient temperature of the store, the proximity of the package to the front of the rack and whether or not the package is in direct contact with a refrigerated shelf or is merely stacked upon other containers.
Thermal abuse may also occur, or may be compounded, when a consumer removes a poorly refrigerated package from such an open refrigerated case and places the refrigerated product in a shopping cart early in an extensive shopping trip. The refrigerated product may therefore be exposed to a~bient temperature conditions for up to several hours untll the package is taken home and placed into a refrigRrator.
Thermal abuse can also occur during normal 6hipping and handling. For example, the refrigeration unlt on a re~rigerated truck or boxcar can break duxing tran~it, thereby expo~ing the paakages and thoir content~ to elevated temperatures for a prolonged period o~ time. In addition, during the shipplng process, containers may wait on a loading dock ~or several hours either prior to being loaded onto a truck or thereafter. -In accordance with the present invention, ~thermal abuse re~i~tance~ can be imparted to liquid egg. In the broadest sense, ~thermal abuse reeistance~ in accordance with the present invention mean~ that liquid egg processed in accordance with the .
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present invention which has been thermally abused will retain a substantially greater portion of its intended re~rigerated shelf life than would liquid egg which has been merely pasteurized under identical conditions and thermally abused to the same extent. For example, egg pasteurized and packaged under identical conditions and exposed to the same degree of thermal abuse, will last longer. Preferably, liquid egg so treated in accordance with the present invention will have at least one day's longer shelf life. Of course, the lesser the degree of thermal abuse, i.e. exposure to lower temperatures for shorter periods of time, the less severe the impact of the exposure. Therefore, by the practlce of the present invention, it may be possible to negate entirely the effects of such minimal abuse and/or allow the liquid egg to retain a much larger percentage of its extended refrigerated shelf life. Thus, for example, liquid egg stored at 45-F which might be expected to have its re~rigerated shel~ life reduced ~rom 12 weeks to 7 weeks, might last for 8 weeks or longer. In addition, the use of electroheating and, ~or example, nisin, in accordance with the present invention, allows the processor to realize not only a low total plate count 25 ~nd thermal abuse resistance, but also a higher level o~ retained baking functionality with little or no detrimental coagulation. This is especially true when the liquid egg o~ the present invention is compared to egg proce~sed by other methods to yield thc same plate count.
The method~ o~ the present invention will be better understood with re~erence to the schematic diagram o~ Fig. 1, which de6cribes a typical device used ~or pasteurizing liquid egg products. Thi~
typlcal egg pa~teurizer has, however, been modi~ied by substitution o~ an electroheater 7' where a plate heat exchanger or other conventional heating device could be used. This and similar devices can also be used in .~ . , . . , . ~ , , 2 ~ 2 ~
connection with the heat treatment of a wide variety of foods.
As shown in Fig. 1, and for illustrative purpose~ only, liquid whole egg, usually in 5 refrigerated form, i8 transferred from a holding tank 1 to a balance tank 2. Liquid egg could also be introduced into the apparatus directly from a tank car, tank truck or from an egg breaking line.
~, Thereafter, the liquid whole egg is pumped through a timing pump 3 which keeps the liquid whole egg moving throughout the entire pasteurization apparatus. The liquid whole egg is then preferably preheated by any conventional means of heatiny such as ovens, vats and/or ~team infusion systems. In addition, electroheating elements or cells of the present invention can also be used to preheat the liquid whole egg. The liquid whole egg is usually brought from re~rigerated or room temperature up to about 139F or higher. More preferably, however, a conventional plate heat exchanger 4 is used to accomplish p preheating.
As shown in Fig. 1, the regeneration y; ~oction 5 of a conventional plate heat exchanger 4 is connect-d to the output o~ timing pump 3. The liquid 2g whole egg temperature is rai~ed in the regeneration ~-ction 5 ~rom, for example, 35~-40F to between elbout 90-F and about 120-F. Thereafter, the liquid whole egg 1~ introduced into the heating section 6 of plate heat exchanger 4 ~or further preheatlng. In heating ~oction 6 the temperature of the liquid whole egg i8 ~urther elevated in temperature to something below pasteurization temperature, usually between about 120-F and about 149-F. In a pre~erred mbodiment, preheatlng temperatures o~ about 123-F and about 149-F and more pre~erably between about 130-F
and about 144-F are used ~or liquid whole egg. Unless relatively high pasteurization temperatures are used, it is generally preferable that the maximum preheating .' 2~ 2~9~.9 temperature be selected such that it is below the pasteurization temperature of the particular form of ~ood being treated. In the context of liquid whole eqg, preheating temperatures generally range up to about 139-F.
Thereafter, the liquid whole egg passes between the electrodes of an electroheater 7~. The electroheater 7' is supplied with a high frequency AC
electric current which is effective to heat the liquid whole egg without electrolysis. Preferably, the AC
electric current has a frequency above about loo Hz and, more preferably, above about loo kHz. Most preferably, freguency used ranges from between about 150 kHz and about 450 kHz. This energy is appl$ed to the liquid whole egg in such a way so as to avoid detrimental coagulation. In electroheater 7' the temperature of the liquid whole egg is elevated from its preheated temperature to the desired pasteurizing temperature. Pasteurization temperatures in excess of 170-F for liquid whole egg can be achieved, however, preferred pasteurization temperatures o~ between about 140F and about 16~F
and more preferably, between about 140~F and about 155-F are achieved. Most preferably, pasteurization temperatures between about 140F and about 145'F ~re used. These temperatures are, of course, ~or liquid whole egg only. For liquid egg white, temperatures should range from between about 124^F (with peroxide) or about 134'F (without peroxide) to about 139-F.
~ ter being electroheated, the liquid whole egg i~ then passed through holding tubes 8 where it is held ~or a period o~ time sufficient to complete pa~teurization in accordance with the Federal Regulation~. Generally, holding times o~ between nbout 0.1 ~econds and about 5 minutes can be used, however, times of between about 2 and about 4 minutes are pre~erred. The liquid whole egg then passes to ~121 Q~9 flow diversion valve 9. If the temperature of the liquid whole egg exiting holding tubes 8 is below a preset value the liquid whole egg is returned to the balance tank 2 to go through another pasteurization pas~. If, however, the exit temperature is at or above the preset value, the liquid whole egg is allowed to proceed via the cooling means 10 to the packager 11, or to a holding tank, tank car, etc.
When cooled by cooling means 10, the pasteurized electroheated liquid whole egg preferably returns to a refrigerated temperature of between about 32F
and 45-F.
Cooling means 10 can be any device useful for lowering the temperature of the electroheated liquid egg, liquid whole egg in this case, quickly enough to avoid detrimental coagulation. When high temperatures, and in particular, temperatures over about 155-F to 160-F and higher are reached during pasteurization, the need to rapidly cool the liquid whole egg become~ acute. In such cases it may be necessary to utilize a nY~-shaped cooling device such as described in the aforementioned U.S. Patent Applicatio-n No. 07/862,198, filed on April 2, 1992.
When, however, pasteurization temperatures are below 160-F and more particularly below 155~F, it i~ ~¢ceptable to use more conventional cooling mean~ 10' ~uch as the cooling/regeneration section and re~rigeration section of a conventional plate heat exchanger. In ~act, coollng means 10' may be the coollng/regeneration and re~rigeration section~ 14 and 16 refipectlvely, o~ plate heat exchanger 4, as ~hown in dashed lines in Fig. 1. In that case, after leaving rlow diversion valve 9, the electroheated liquid whole egg would flow into the cooling/regeneration ~ection 14 o~ plate heat exchanger 4 via conduit or pipe 12 where its temperature would be lowered to between about 120-F
and about 60-F. Therea~ter, the cooled liquid whole : . :
2~ .9 egg would be refrigerated in the refrigeration section 16 of heat exchanger 4 where its temperature would be lowered to between about 32F and about 45F
and, more preferably, between about 32F and about 40-F. Thereafter, the refrigerated liquid whole ; egg could be stored, loaded into a tank car or truck or packaged in packaging device or packager 11.
Packaging device 11 need not be aseptic. By ; electroheating and storage at 40F or under, it is not ; 10 nece~sary to aseptically package processed pasteurized liquid egg in order to obtain an extended refrigerated shel~ life and, more particularly, an extended re~rigerated shelf life of eight weeks or more.
Aseptic packaging procedures are described in 21 C.F.R. 113.3, 114.40(g) and 113.100(a)(4).
Generally during aseptic processing, a commercially sterilized product is introduced into a sterile package under sterile conditions such that the filling and sealing of the package is all conducted in a sterile environment. Of course, liquid egg in ! accordance with the present invention and the ma~orlty known technology i8 not sterile. Nonethele6s, a~eptic packaging procedures insure that a tatistlcally lnsigni~icant number of cells are ~5 lntroduced during packaging. For purposes of lllustration only, aseptic packaging should introduce i approximately one cell per 1,000,000 packages.
Asoptic packaging can be accomplished using an International Paper Model SA aseptic packager or a 8cholle Model 10-2E aseptic packager. Of course, ~eeptic packaging may be utilized in accordance with the present invention. However, because of the present invention, it need not be.
Another type o~ packaging userul in accordance with the present invention is the so-called ~clean pack~ which may be produced using a Cherry-Burrell packager Model EQ3 or EQ4. This type of packaging has a higher failure rate or, more correctly 2 1 2 ~
put, a higher incidence of the introduction of microorganisms during packaging than a truly aseptic system. For illustration purposes only, a clean pack may introduce one cell per every 100,000 packages.
S While the u~e o~ this packaging technology does not qualify as a~eptic, it is certainly acceptable in terms of the present invention and such devices may be used as packaging device 11. These Cherry-Burrell packages can also be run so as to produce plain ~anitized clean containers as discussed below. For example, if the packages are not treated with a peroxide spray prior to filling, they can be considered sanitized, but not aseptic or ~clean packs.~ These are both forms of extended refrigerated shelf li~e packages.
Also useful in accordance with the present invention are plain sanitized clean containers produced and sanitized using ~good manufacturing procedures~ in accordance with all government regulations. Such containers which have been properly sanitized may introduce as many as, for illustration purposes only, one cell per hundred packages. Because of the superior kill provided by electroheating and the growth inhibitory effect of proper re~rigerated storage, ~uch an addltion o~ cells is not considered ignl~lci~nt.
~ he~e aforementioned packages, which are all ~pecifically useful in practicing the present invention to provide extended shelf life, may be contra~ted with a ~dirty package~ which has not been ~anitlzed nor packaged under clean or aseptic conditions. Such containQrs may introduce 1,000 cells per package or more which is statistically signi~icant relativ~ to the number Or cells remaining in pa~teurized liquid egg after succes~ful pa~teurization. Any other type Or package can be utilized, as individual customers may require. Of course, the introduction of any microorganisms after 7` ~ , . .
2121~
treatment is to be avoided at all costs. However, the packaging processes described herein do not significantly increase the total plate count and, therefore, should not affect refrigerated shelf life.
With this overview in mind, the various aspects of the ; present invention will now be described.
In accordance with the present invention, sufficient antibacterial agent is added to the liquid egg so as to provide long term thermal abuse resistance thereto. If, for example, nisin is added prior to pasteurization, there is some evidence that it will also assist in providing a more efficacious pasteurization~ However, the amount of nisin remaining within the resulting liquid egg may be reduced, thereby compromising the degree of thermal abuse resistance which may be imparted. Therefore, it may be advantageous to add nisin or other antibacterial agents in accordance with the present invention to the liquid egg after pa~teurization.
However, it i8 also possible to pasteurize liquid egg using, for example, nisin and then augment the nisin content o~ the egg after pasteurization.
The amount of antibacterial agent useful in acaor~ance with the pre~ent invention can vary widely depending upon the extent of the initial kill of mlcrobes provided by pasteurization, the relative chance o~ thermal storage abuse, the degree and extent o~ anticipated thermal storage abuse, the particular antibacterial agent or agents u~ed and the anticipated extended refrigerated shelf life of the resulting liquid egg. For nisin, an amount of at least about 0.75 mg/kg of liquid whole egg should be used. More pr-rerably, between about 1.25 mg/kg and about 250 ~g/kg o~ ni~in may be used. The amounts of other ~ntlbncterial agents can be ad~usted so as to provide a level of efficacy substantially corresponding to the u~eful levels of nisin.
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The efficacy of the addition of such antibacterial agents may be enhanced by the addition of a chelating agent or a surfactant agent as described in U.S. Patent No. 5,135,910, the text of which i8 incorporated by reference. Chelating agents used in accordance with the present invention may include EDTA, CaEDTA, CaNa2EDTA, and other alkyldiamine tetraacetates, EGTA, citric acid, and citrate. Surfactants as described herein may include lo tweeng, tritons, glycerides, fatty acids, quaternary compounds, sodium dodecyl sulphate and cocamido propyl betaine. These can be present in an amount of between about 0.1 mM to 20 mM.
In addition, it i8 also known that compounds auch as nisin can be used in combination with glycanohydrolases to provide particularly efficacious kill~ during pasteurization. It is believed that the coaction of these various agents, such as lysozyme, will also be efficacious in providing enhanced thermal abuse resistance. Lysozyme, for example, may be added in an amount of between 0.1% and about 1.0% by weight.
These additional ingredients may be added bofore, during or after pasteurization. They may be ~dded with the antibacterial agent or separately. I~
2S Added b~rore pa~teurization, it may also be desirable to aug~ent these materials as they may be digested durlng hoating.
Consistent with the belief that the combination of a particularly ef~icacious kill and the u~o o~ ~n antibiotic agent such a~, for example, ni~in, can provide significant thermal abuse rQ~i~tanoe during storage, a preferred aspQCt of the pro~ent invention involves electroheating the liquid egg a~ previou~ly described ~uch that the total initial plate count of the liquid egg is under about 50. Howevor, the liquid egg mu~t be treated in ~u¢h a way that its baking functionality is ~ub~tantially retained and the detrimental coagulation :: ' , ,.. ', ". ,.' .,;,, ' ,,'., , . ' ' ,, . , :, ' ' .
2~2~
attendant certain pasteurization processes is minimized. Thus higher temperature techniques such as tho~e disclosed in Jones et al., U.S. Patent No. 3,113,872, and Sw~rtzel et ~1 ., U . S . Patent No. 4,808,425, are generally contraindicated. Of course, 6uch techniques may be useful in accordance with the present invention. However, they are believed to be unable to provide the extremely efficacioug kill with little or no sacrifice in terms of detrimental coagulation and baking functionality as called for in this aspect of the present invention.
In accordance with this preferred aspect of the present invention, liquid egg is electroheated, with or without the addition of nisin, to a temperature of between about 140F and about 145F and is held at that temperature for approximately 3.5 minutes. Thereafter, nisin or other similar agents may be added and the product is packaged and stored under refrigerated conditions. Preferably, a storage temperature of 40-F or below is maintained. If the resulting package liquid egg is stored improperly for any length o~ time, the combination of the partlcularly low kill and the antibacterial agent such as nlsin should provide significant protection against epoilage.
The foregoing will be better understood with rererence to the following examples. The6e examples ar- for purposes o~ illustration. They are not to be con~idered limiting as to the scope and nature o~ the pre~ent lnvention.
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Six two pound gable top containers containing liquid whole egg electroheated to a t~mperature o~ 147-F and held at that temperature ~or approximately 3 1/2 minute~ were removed from a processing run. The liquid egg was packaged using a Cherry-Burrell model EQ3 packager which provides for a so-called ~clean pack~. The liquid whole egg included 1: , , ,. , ;, , .
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2~ 2~ 989 citric acid in an amount which was insufficient to provide any preservative effect but was useful for stabilizing the color of the egg yolk. The treated liquid egg has an approved ten week refrigerated shelf life. 200 milligrams of NISAPLIN, available from Barrett Ltd. Trowbridge, Wilts, England BA148TR, in ~olution was injected through the container using a sterile syringe. One milligram of NISAPLIN contains about 0.026 milligrams of nisin, i.e., NISAPLIN is about 1/40th nisin by weight. Thereafter, the introduction hole was taped shut. Four of the six container6 were treated in this way. The remaining two containers were used as a control. Each of these were punctured with a sterile syringe and thereafter were taped shut. The six containers were then stored in a windowless room at an ambient temperature which ranged from between about 68~F and about 75'F.
Four days after treatment both of the controls had turned 60ur. They were characterized by strong smell, high viscosity, and uncharacteristically bright yellow color. The plate counts were too high to mea~ure. The liquid egg in two of the four test containers had begun to show some signs of thickening.
Tho plat~ counts for these two samples were also too j 25 high to measure. However, they did not have an ob~ectlonable smell. ~y standard observation, it was believed that the~e containers included egg which was 8a~e ~or consumption at that moment. However, there WAO at least a 50% chance that khe egg would become lnedlble within 24 to 48 hours.
The remaining two samples of egg treated in accordAncQ wlth the present invention showed no signs of thlckenlng, discoloration or other physical change.
The egg contained in these second two containers did not include an ob~ectionable smell and tasted fresh and sweet. Total plate counts of 500 and 600 were ,, observed.
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- . -23-The electroheated liquid egg in accordance with Example 1, when stored at room temperature between 2 and 3 days, turned sour and spoiled.
However, by the use of nisin in accordance with the present invention, the liquid egg was still safe to consume and palatable for 4 to 5 days or longer. This represents almost a 100% increase in the shelf life of the liquid egg even over egg which had been electroheated. Liqjuid egg treated by conventional plate heat exchangers, for example, at 147F or so would be unlikely to last for more than 1 to 2 days be~ore 8poiling. Thus the practice of the present invention including both electroheating to provide a particularly e~icacious kill in combination with an antibacterial agent such as nisin can provide a significant increase in storage stability over conventionally pasteurized egg.
This rather rigorous test exemplifies the advantages of the present invention when liquid egg is stored on a countertop at room temperature. Of course, if liquid egg was merely stored under improper re~rigeration conditions such as, at between about 45-F and 50'F, the extended refrigerated shelf ~ o~ the liquid egg would not be reduced to only 5 or ~ore day6. Under such conditions, particularly if the lmproper storage does not periist, the extended re~rigerated ~helf life of the egg may be ~ignificantly retained 80 that the liquid egg may be ~tored ~or as much as 6 to 8 weeks or more.
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The six containers described in Example l were re~ealed and held at room temperature for four additional days. When the two control containers were opened, a ~trongly rotten odor was given off. Visible 3S colonies o~ bacteria were present in the egg and the gg had noticeably thickened and darkened in aolor.
The four cartons containing electroheated liquid whole egg and nisin had also become thick and turned Aour.
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The pH of all six containers was about 5.3. In addition, while a sour fermentative odor was detected, the rotten odor normally associated with egg turning bad was not noticeable.
~a~e~rL~
Six additional containers of liquid egg as described in Example 1 were prepared and stored. 300 mg of NISAPLIN was introduced into two containers, 400 mg of NISAPLIN was introduced into two containers and 500 mg of NISAPLIN was introduced into the last two containers. The four containers including 300 and 400 mg of NISAPLIN were observed to be thick, their color had changed, and a sour odor was present.
The pH of the samples was about 5.45. The two containers including 500 mg of NISAPLIN, however, were per~ect in terms o~ color and viscosity. Their smell was sweet and their viscosity was about 6.75. The six containers were stored for eight days at room temperature of between about 68F and about 75F.
x~mpl~ ~
Ten thousand pounds of TABLE READY brand liquid whole egg from Papetti'6 Hygrade Egg Products, Inc. o~ Elizabeth, New Jersey were pasteurized by electroheating at a temperature of approximately 143-F
2S and held at that temperature for approximately three ~nd a hal~ minutes. The liquid egg was packaged using a Cherry-~urrell Model EQ3 Packager which provides for ~o-called ~Clean Pack~n. Three pounds of NISAPLIN was dis~olved in forty pounds of water and introduced into the liquid whole egg whlle the egg was in the holding tank prior to pasteurization. A~ter processing the containere, including liquid whole egg pasteurized in the pre~ence o~ nisin, were stored at either 40-F
or 50-F, both of which can broadly be considered ~rerrlgerated~ temperatures. Controls consisting of TABLE READY liquid whole egg were processed and packaged under the same conditions as described herein, without the addition of NISAPLIN. The - .. -. - . . .. .. ., : . . .. .
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controls were actually processed a day before the NISAPLIN containing samples. The amount of NISAPLIN
used equated to approximately 7.8 mg. per ounce or 27.5 mg. per hundred grams of liquid whole egg.
The amount of nisin thereby delivered was approximately 0.20 mg. per ounce or approximately 0.68 mg. per hundred grams. The results are reported in Table I.
TABLE I -~
~Ni~in wa~ ~dd-d b~rOre pal~t~urization) ~)UIPLE O _ ~ _ l~vl~ s 6 V _ 10 IIUI~L~10 60 L'r ~00 ~C0 L'r 10: = 11)0 L~ 00 L~ 100 100 Dr 100 LT 100 colmoL lo LT 100 LT 100 LT 100 LT 100 LT 100 L7,' 100 LT 100 ll,50o 150,000 TN~C
__ _ _ _ g~FLE 10 LT 100 20 L'r 100 LT 100 LT 100 LT 100 LT 100 8,900 TNTC TNTC
CO~XL _ L'r 1-0 L'r lOD ~C _ TNTC TNTC TNTC TNTC TNTC TNTC
L~V~LS U~ED NI~PLIN 7 8 ~g /02 . LT- L--~ Tllan 27 5 ~9/100 g TNTC - Too Nu~lrou- to Coune NI8IN 0 20 ~g/oz 0 68 ~19/lOO 9 At 40-F, the controls exhibited a ~igni~icant increase in total plate count between the 25 ~eventh and eighth week. By the ninth week, the ~ample~ opened were no longer consumable. In contra~t, the sample containing NISAPLIN continued to have acceptable total plate counts for a ~ull ten wo~ks .
The llguld egg stored at 50~F, without NISAPLIN, lasted approximately two weeks before the tot~l plate count increased to the point where the number o~ bacterla were too numerous to count. In contrsat, liquid egg processed according to the 3S preaent lnvention, including NISAPLIN, did not exhibit a signi~icant increase in total plate count until Week 8 at which point, the liquid egg was still con~umable.
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. .: . . . . .. ,: , .
,~ , . , , , , " ~ . . . ... .. .
This test underscores not only the importance of the discovery of the present invention, but al80 the unexpected nature of that discovery. As prevlously de~cribed, it has been reported that nisin used at levels of 5 mg. per liter resulted in an increase in refrigerated shelf life of pasteurized liquid whole egg. Indeed, as exemplified by the samples stored at 40, the use of nisin, particularly in combination with electroheating, can provide an enhanced and extended refrigerated shelf life. Of course, it should be noted that without the use of electroheating (as was the case in the reported literature), the shelf life of the pasteurized liquid egg, both with and without nisin was considerably shorter than exemplified herein. However, when stored at 50-F, a significant and unexpected difference in the keeping qualities of the liquid egg was observed.
Electroheated liquid egg having an extended refrigerated shelf life by virtue of the electroheating process alone spoiled in under three weeks. If properly stored, electroheated liquid egg would be expected to have an extended refrigerated shel~ e o~ 8-10 weeks. With the addition of nisin, however, the llquid whole egg retained most of the predicted shelf life lastiny between eight and nine week~ prior to epoilage. Such a profound difference in abuse re~lstance could not have been predicted based upon the e~ects of nisin on extending re~rigerated ~hel~ life.
~ L~
Liquid egg was processed and prepared as de~cribed in Example 1 with 7.8 mg. per ounce of NISAPLIN being in~ected into the already processed egg ~eal-d within a container using a sterile syringe.
3S The resulting containers were stored at 50F and te~ted as previously described. Initial testing of the liquid egg exhibited a total plate count of 10. A
~econd container was opened at the end of Week 1, and 2 t ~ 9 -27- ~
:
the total plate count again was less than 10. A third container was opened at the end of the second week, and the total plate count was 30. A fourth container WA8 opened at the end of three weeks, and the total plate count was less than lo. After four weeks, another sample was tested, and the total plate count was 360. Samples were also tested at Weeks 5, 6, 7, 8, 9 and lo. However, in each case, the total plate count was too numerous to count. This shows that particularly unexpected results are obtainable by the use of nisin, prior to pasteurization, in combination with electroheating.
~x~m~10 6 Additional containers of TABLE READY brand li~uid whole egg were prepared as described in Examples 1 and 5. However, into each, NISAP~IN in the amount of 15.6 mg. per ounce or 55.0 mg. per hundred grams was injected. The initial total plate count was 10. The plate count after one week was 10. After the second and third weeks, the total plate count was less than 10. A~ter four weeks, the total plate count wa~ 10. Individual samples checked in Wee~s 5 and 6, however, had plate counts that were too numerous to count. These last two examples illustrate that nisin 2S i~ u~e~ul, both be~ore and after pasteurization, and at levels quite unexpected over the art.
The principles, preferred embodiments, and mode~ of operation Or the pre~ent invention have been d~aribsd ln the foregoing specirication. The invontlon which iG intended to be protected herein, however, is not to be construed as limited to the particular embodiments disclosed, since these are to be regarded illustrative rather than restrictive.
Varlation~ and changes may be made by others without departlng from the spirit and scope of the invention.
Claims (19)
1. A method of imparting thermal storage abuse resistance to liquid egg comprising electroheating said liquid egg and holding said electroheated liquid egg for a period of time sufficient to pasteurize said electroheated liquid egg, characterized by adding to said liquid egg at least one antibacterial agent which is effective against gram positive bacteria in an amount which is effective to provide thermal abuse resistance to said liquid egg.
2. The method according to claim 1, wherein said antibacterial agent is added prior to the step of electroheating said liquid egg.
3. The method according to claim 1 or 2, wherein said antibacterial agent is nisin, and is added in an amount of at least about 0.75 mg/kg of said liquid egg.
4. The method according to claim 3, wherein said nisin is added in an amount of at least about 1.25 mg/kg of said liquid egg.
5. The method according to claim 4, wherein said nisin is added in an amount of between about 1.25 and about 250 mg/kg of said liquid egg.
6. The method according to claim 1, including adding to said liquid egg and said antibacterial agent at least one edible chelating agent, at least one edible surfactant or at least one glycanohydrolase.
7. The method according to claim 6, wherein said edible chelating agent is selected from the group consisting of EDTA, CaEDTA, CaNa2EDTA, and other alkyldiamine tetraacetates, EGTA, citric acid, and citrate.
8. The method according to claim 6, wherein said surfactants are selected from the group consisting of tweens, tritons, glycerides, fatty acids, quaternary compounds, sodium dodecyl sulphate and cocamido propyl betaine.
9. The method according to claim 6, wherein said glyonohydrolase is lysozyme.
10. A method of storing liquid egg which has been rendered resistant to thermo storage abuse comprising providing the liquid egg and electroheating said liquid egg, characterized by adding an antibacterial agent to said liquid egg which is effective against gram positive bacteria in an amount of at least about 0.75 mg/kg of said liquid egg, electroheating said liquid egg and holding said liquid egg for a period of time sufficient to provide an initial average total plate count of 50 or less, and storing said liquid egg at a temperature above 40°F
for at least some portion of time.
for at least some portion of time.
11. The method according to claim 10, wherein said antibacterial agent is nisin.
12. The method according to claim 11, wherein said nisin is added in an amount of at least about 1.25 mg/kg of said liquid egg.
13. The method according to claim 12, wherein said nisin is added in an amount of between about 1.25 and about 250 mg/kg of said liquid egg.
14. The method according to claim 10, 11, or 12, including adding to said liquid egg and said antibacterial agent at least one edible chelating agent, at least one edible surfactant or at least one glycanohydrolase.
15. A method of imparting thermal storage abuse resistance to liquid egg comprising electroheating said liquid egg characterized by adding to said liquid egg at least one antibacterial agent which is effective against gram positive bacteria in an amount which is effective to provide thermal abuse resistance to said liquid egg, and electroheating said liquid egg and holding said liquid egg for a period of time sufficient to provide an initial average total plate count of 50 or less, under conditions which will minimize detrimental coagulation and maximize retained baking functionality.
16. The method according to claim 15, wherein said antibacterial agent is nisin and is added in an amount of at least about 0.75 mg/kg of said liquid egg.
17. The method according to claim 16, wherein said nisin is added in an amount of at least about at 1.25 mg/kg of said liquid egg.
18. The method according to claim 17, wherein said nisin is added in an amount of between about 1.25 and about 250 mg/kg of said liquid egg.
19. The method according to claim 15, 16, or 17, including the step of adding to said liquid egg and said antibacterial agent at least one edible chelating agent, at least one edible surfactant or at least one glycanohydrolase.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US15462493A | 1993-11-18 | 1993-11-18 | |
| US08/154,624 | 1993-11-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2121989A1 true CA2121989A1 (en) | 1995-05-19 |
Family
ID=22552084
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2121989 Abandoned CA2121989A1 (en) | 1993-11-18 | 1994-04-22 | Thermal abuse resistant egg |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA2121989A1 (en) |
| DE (1) | DE4415751A1 (en) |
| GB (1) | GB2283900A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2815226B1 (en) * | 2000-10-17 | 2003-02-07 | Edoardo Ruga | PROCESS FOR CONDITIONING AND STORING AT ROOM TEMPERATURE OF PASTEURIZED LIQUID EGG |
| US7211287B2 (en) | 2004-06-24 | 2007-05-01 | Cargill, Incorporated | Egg Products |
| US20100129501A1 (en) * | 2007-07-20 | 2010-05-27 | Cargill, Incorporated | Methods and compositions for preserving egg products |
| CN105076351A (en) * | 2014-05-15 | 2015-11-25 | 北京德青源农业科技股份有限公司 | Preservation method of egg liquid |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5135910A (en) * | 1988-06-22 | 1992-08-04 | The Public Health Research Institute Of The City Of New York | Nisin compositions for use as enhanced, broad range bactericides |
| US4980163A (en) * | 1989-03-01 | 1990-12-25 | Public Health Research Institute Of The City Of New York | Novel bacteriocin compositions for use as enhanced broad range bactericides and methods of preventing and treating microbial infection |
| US5290583A (en) * | 1992-04-02 | 1994-03-01 | David Reznik | Method of electroheating liquid egg and product thereof |
-
1994
- 1994-04-22 CA CA 2121989 patent/CA2121989A1/en not_active Abandoned
- 1994-04-26 GB GB9408376A patent/GB2283900A/en not_active Withdrawn
- 1994-05-04 DE DE19944415751 patent/DE4415751A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE4415751A1 (en) | 1995-05-24 |
| GB9408376D0 (en) | 1994-06-15 |
| GB2283900A (en) | 1995-05-24 |
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