GB2282953A

GB2282953A - Method of treating a raw carcass

Info

Publication number: GB2282953A
Application number: GB9420560A
Authority: GB
Inventors: Robert M Elder; Claire H Hughes
Original assignee: Moy Park Ltd
Current assignee: Moy Park Ltd
Priority date: 1993-10-12
Filing date: 1994-10-12
Publication date: 1995-04-26
Anticipated expiration: 2014-10-12
Also published as: GB9420560D0; GB2282953B; GB9321008D0; GB2282953A8

Abstract

A method of treating a raw carcass comprises applying thereto a buffered aqueous solution of a carboxylic acid, e.g. lactic acid, acetic acid or propionic acid.

Description

TITLE: Method of treating a raw carcass DESCRIPTION This invention relates to a method of treating a raw carcass, especially of a bird, such as a chicken or turkey.

It is well known that a substantial reduction of the pH value of some foodstuffs is sufficient to contain many spoilage microorganisms and common uses of this technique are to be found in pickles and sauerkraut. In the case of milk processing where rennet and lactic acid bacterial starter are used to produce cheese the latter has a long life, without spoilage, due to its lactic acid content which can keep cheese at a pH value as low as 4.8. Normally growth only occurs within the range pH 6 to pH 9. When birds are processed in the factory to produce poultry carcasses there is a dispersal of microorganisms during plucking and evisceration which causes a resultant increase in bacterial contamination of the carcass.Within the poultry industry in the United Kingdom it is normal for air chilled chicken to be washed in super-chlorinated water which has been chlorinated to a level of 60pm either by the injection of chlorine gas or a concentrated solution of sodium hypochlorite into the wash water. This treatment is sufficient to remove the gross contamination of the skin and the abdominal and thoracic cavities of the chicken, but in the presence of oxidizable organic material the effect is nullified or reduced by the formation of chloramines or sodium chloride or both.

There is a need, therefore, for a method of creating bacteriostatic conditions on the surface of the whole raw bird at a stage where the chlorine water wash is finished and the packaging stage has not yet begun.

An object of this invention is to provide a method of treating a raw carcass, especially of a bird in order to extend its shelf-life.

According to this invention there is provided a method of treating a raw carcass comprising the steps of applying to the carcass a buffered aqueous solution of a carboxylic acid.

The carboxylic acid used in the method of the invention is preferably one that will not impart any undesirable properties to the carcass, such as in terms of taste. Suitable carboxylic acids for use in the invention include lactic acid, acetic acid and propionic acid.

It is preferred that the buffered aqueous solution of carboxylic acid, especially of lactic acid, have a pH in the range of 2.8 to 3.2, especially about 2.9.

A preferred buffered solution for use in the invention is an aqueous solution made by dilution of 13, especially 2% by weight of a concentrated solution containing about 60% by weight lactic acid, about 20% by weight alkali metal salt of lactic acid and balance water.

When innovatory processing was being considered, which lead to the present invention, lactic acid and its salts as the buffering agents where chosen for pH control of the carcass surface. This was done because lactic acid was known to be completely safe in food processing and had already been allocated the food additive number E.270 in the E.C. but was basically only used to protect various foods against mould growth. An aim of the previously mentioned experimental processing was to develop lactic acid and its salts, as buffers, so that their presence on the entire surface of the raw bird would create a specific bacteriostatic environment.

In this context it should be noted that lactic acid and its derivatives are not foreign to flesh in general, and the skin in particular, because it has been estimated that the Stratum Corneum contains as much as 10% lactic acid and its salts and at various times in the literature it has been described as part of the skin's natural moisturising factor. Lactic acid is highly substantive to the skin and hair and affects the texture of proteinaceous materials causing softening and swelling of the skin with endowed increased elasticity which results in more pronounced skin follicles which enhances appearance and presentation. In order to buffer the- aqueous solution of lactic acid, a preferred buffer is an alkali metal salt of lactic acid. Sodium lactate and potassium lactate are preferred buffers for the lactic acid solution in the method of the invention.

The strategy of employing lactic acid and its salts as a buffered solution on raw flesh is two fold because such mixtures serve to stabilise the pH value of the treated flesh outside the range 6 to 9 and since sodium and potassium lactates are powerful humectants, being more hygroscopic than glycerol, they reduce the Water Activity AW of the carcass surface below 0.9 which in its turn reduces, or even stops, the active metabolism of most microorganisms.

Therefore the need alluded to in the above preamble may be fulfilled in a preferred embodiment of the present invention where there is provided a method of extending the shelf-life of raw poultry meat by spraying the carcass externally and/or internally with a buffered lactic acid solution which can be used directly as an aqueous solution, or as an aqueous solution whose viscosity has been increased by the use of a permitted thickening agent, or as an oil in water emulsion of poultry fat. The process of carrying out the method is preferably by means of in-line sprays for external surface application and probe spray heads for the treatment of abodiminal and thoracic cavities. The method of the invention is preferably carried out prior to chilling or freezing of the raw carcass.Because the carcass will probably be at an elevated temperature due to the plucking and evisceration processes, it is preferred that the buffered aqueous treatment solution be at a compatible temperature for application to the carcass, especially at least at the temperature of the carcass. Typically the treatment solution will be at a temperature of the order of 30 to 450C, especially at around 400C.

On the other hand, the treatment of the invention may be carried out at any other suitable stage of the processing of carcasses. Possibly the treatment of the invention may be carried out prior to the washing with super-chlorinated water, in which case a higher concentration of lactic acid may be desirable in the treatment solution than in the preferred method of the invention.

The invention will now be further described by means of the following Examples, in which all percentage compositions are expressed in terms of weight for weight.

EXAMPLE 1 A buffer was prepared by mixing 60% of lactic acid with 20% of sodium lactate and then adjusting the mixed volume to 100% by the addition of water to yield a slightly syrupy yellow liquid. This concentrated stock buffer solution was used as a 2% treatment solution in water which has a stabilised pH value of 2.9. It was maintained at a temperature of about 400C and then sprayed onto the skin and into the cavities of partially prepared birds which were on the production line on their way to the pre-chill station.

EXAMPLE 2 The diluted buffer solution (2%) of EXAMPLE 1 was stirred with 0.25% w/w of ASCMC (sodium carboxymethyl cellulose), which has a designation-E.466 in the Food Additive Regulations, when a low viscosity solution was obtained. This solution was used by the spray apparatus technique at about 400C and because of the selected grade of SCMC it was found that a buffer film of 2 to 21/2 times the thickness of the simple film of Example 1 could be obtained. This extra film thickness is useful in the maintenance of skin and internal membrane pH value which tends to rise with tome as the buffered film is diluted with body fluids during eventual osmotic rquilibrium which occurs after some hours of storage.

EXAMPLE 3 The buffered solution (2%) of Example 2 was converted into a dilute oil-in-water emulsion using 3% to 5% of poultry fat dispersed in the aqueous phase by the use of an improved food emulsifying agent with an H.L.B. (Hydrophyllic-Lipophyllic Balance) in the region of 6 to 7. As an example of this embodiment one could use sodium strearyl-2-lactylate (E.481) but others are available from the E-List. High speed shear stirring at 50 to 600C is all that is required to produce a suitable spraying emulsion when a dispersion of E.481 in the warm poultry fat is added to the warm buffer. The presence of natural chicken fat in the sprayed buffer solution leads to an enhanced appearance in terms of gloss and pronounced skin follicles.Using the described spraying technique with any of the reagents of EXAMPLES 1, 2 or 3 as a decontaminant film applied at the pre-chill point of primary processing it was found that during the storage period of 14 days there was a noticeable reduction in microbial growth on buffered lactic acid treated birds compared to untreated (control) birds and the difference between control and treated birds was significant throughout the storage period. For example the TVC (Total Visible Count) on the 14th day differed by common log 2.9. Also it was found that Pseudomonas.spp. was reduced on "Day O" by as much as common log 1.6 and this is attributed to the initial microbiocidal effect which is apparent when the pH value of the carcass surface is immediately reduced on contact with the sprayed buffer film.

The organoleptic results showed that a trained taste and- odour panel could discern no deleterious effects with the use of these 2% buffered lactic acid reagents and further, with extended storage (by "Day 9") the odour, flavour and texture of the buffer treated birds were "good" (equivalent to a score of 4) while those attributes on the control birds were "average" (equivalent to a score of 3). As a result of these disclosures those skilled in the art will realise that decontamination of raw whole birds with the described buffered lactic acid solutions results in a safer product with longer shelf-life, with very acceptable organoleptic properties, and does so with no threat to consumer health.

Claims

1. A method of treating a raw carcass comprising the step of applying to the carcass a buffered aqueous solution of a carboxylic acid.

2. A method as claimed in claim 1, wherein the carboxylic acid solution has a pH in the range of 2.8 to 3.2.

3. A method as claimed in claim 1 or 2, wherein the carboxylic acid is lactic acid.

4. A method as claimed in claim 3, wherein the lactic acid solution is buffered by means of a salt of lactic acid.

5. A method as claimed in claim 4, wherein the buffer is an alkali metal salt of lactic acid.

6. A method as claimed in any one of claims 1 to 5, wherein the aqueous solution contains a thickening agent.

7. A method as claimed in claim 6, wherein the thickening agent is sodium carboxymethyl cellulose.

8. A method as claimed in any one of claims 1 to 5, wherein the acid solution is in the form of an oil in water emulsion.

9. A method as claimed in claim 8, wherein the emulsion is with poultry fat.

10. A method as claimed in claim 9, wherein the poultry fat is present in an amount of 3 to 5% by weight.

11. A method as claimed in claim 8 or 9, wherein the emulsion contains an emulsifying agent with a Hydrophylic-Lipophyllic Balance in the range of 6 to 7.

12. A method as claimed in claim 11, wherein the emulsifying agent is sodium stearyl-2-lactylate.

13. A method as claimed in any one of claims 3 to 12, wherein the lactic acid solution comprises 1-3% by weight of an aqueous mixture containing 60% by weight of lactic acid 20% by weight of alkali metal lactate.

14. A method as claimed in any one of claims 3 to 13, wherein the lactic acid solution is applied at a temperature in the range of 30 to 450C.

15. A method as claimed in claim 14, wherein the lactic acid solution is applied at a temperature of about 400C.

16. A method as claimed n any one of claims 3 to 13, wherein the lactic acid solution is applied at least at the temperature of the carcass.

17. A method as claimed in any one of claims 10 to 16, wherein the acid solution is applied by spraying.

18. A method as claimed in claim 17, wherein the acid solution is applied by means of in-line spray heads for external carcass surfaces.

19. A method as claimed in claim 17 or 18, wherein the acid solution is applied by means of probe spray heads for treatment of carcass cavities.

20. A method as claimed n any one of claims 1 to 19, wherein the treatment solution is applied to the carcass prior to chilling or freezing of the carcass.

21. A method of treating a carcass as claimed in claim 1 and substantially as hereinbefore described with reference to any one of the foregoing Examples.