MEAT PRESERVATION

Abstract: The sheft-life of fresh meat may be extended by the application to the surface of the meat of a solid material which is capable of releasing acetic acid in the presence of moisture. The meat to be treated is preferably substantially dry and sufficient solid material is added to provide from 0.19-1.88 mg/sq.cm. of acetic acid. Preferred compounds are the complexes of acetates and acetic acid, particularly sodium diacetate. Application may be by dusting or electrostatic spray. The method is applicable to any kind of meat (beef, pork, poultry, fish, shellfish) and shelf-lives as determined by the standard plate count procedure can often be more than doubled.

Description: MEAT PRESERVATION This Invention relates to the preservation of meat products. The marketing potential of a wide range of meat (by which is meant all varieties of animal flesh, including poultry and marine animals) is often limited by shelf life considerations, particularly when the products are to be exported. Deep freezing is an effective but costly approach to reaching export markets, and quality is Invariably affected adversely. As a consequence, there is great interest in the development of processes to improve the keeping quality of fresh products. One method of meeting this need is to use acetic acid which, in the form of vinegar, has been known as a preservative since ancient times, and has been applied in such processes as pickling. Microbiological studies of its effectiveness date from more recent times - for example the work of Levine A.S. and Fellers C.R. (Bacteriology, Vol. 39. p. 499 (1940)). The abovementioned method has resulted from work done in Australia by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and 1t utilises acetic acid washing to increase the shelf Hfe of chilled fresh vacuum-packed beef and sheep carcasses. The method Involves treating the carcass at 55°C with 1.5% acetic add and results in an increase of approximately 50% in the shelf-Hfe of the products. This procedure has been accepted by local exporters and foreign importers, and approval for its application with respect to the United States has been given via appropriate food regulations . The disadvantages of this method include the need to operate at higher than normal ambient temperatures and the requirement for solution treatment of the carcass with resultant requirement for constant monitoring of the acetic acid concentration to ensure that carcass water and exudates do not dilute 1t and thereby reduce its effectiveness. In addition, an increased shelf-Hfe of approximately 50%, while of benefit, leaves substantial room for further improvement. There has now been discovered a process which not only overcomes the abovementioned disadvantages but which also allows the attainment of a substantially increased shelf-Hfe. There is therefore provided, according to the present invention, a method for the treatment of fresh meat such that its shelf life 1s extended, the method comprising applying to the surface thereof a solid material which will liberate acetic add 1n the presence of moisture. As previously indicated, "meat" in the context of this invention refers to any animal flesh suitable for human consumption and 1s considered to Include not only beef, mutton, lamb and pork but also poultry or game birds and marine animals such as fish, shellfish and crustaceans. The solid material is one which will liberate acetic acid in the presence of moisture. One well- known substance which will do this 1s sodium diacetate which on complete dissolution in water is present as a mixture of sodium acetate and acetic add. This substance 1s already known and used as a food additive. For example, rope and/or mould in bread, cheese and malt syrups can be controlled by the addition of sodium diacetate to the foodstuff concerned. The use of this substance for grain and silage preservation has also been proposed, as has its use to improve the palatability of animal feed. A further food-related use is the use to provide the vinegar flavour in various snack foods such as "salt and vinegar"-flavoured potato crisps. In connection with meat, sodium diacetate is known as an additive in some sausage meats (see, for example, "Ordinance on amendment of meat ordinance" ("Verordnung zur Anderung der Fleisch-Verordnung" ) of 25th August, 1969 by the Bundesminister fur Gesundheitwesen, Federal Republic of Germany as reported 1n the "Archiv fur Lebensm1ttelhyg1ene" 20(9) (September 1969) at p.213). However, there 1s no known use of, or proposal to use, sodium diacetate in the nanner of this invention. Sodium diacetate is preferred for use in this invention as 1t has the advantage of already being a recognised food additive. It has been declared "generally regarded as safe" by the United States regulatory authorities and 1s exempted there from residue tolerance limits. Substances other than sodium diacetate which release acetic add on exposure to moisture are also useful in this invention. These substances are, like sodium diacetate, "complexes" of monovalent and divalent acetate salts and acetic acid, wherein the acetic acid is believed to be held in the molecule in a manner analogous to the water of crystallisation in a crystalline hydrated salt. On dissolution, the "complex" readily dissociates and, in the case of sodium diacetate, the result 1s a solution containing sodium acetate and acetic acid. The acetic add is present in an approximately equimolar mixture of undissodated and dissociated species due to the production of a buffered medium at a pH approximately equal to the p a of acetic acid. Depending on the amount of water present, the acetic acid concentration can be very high. In the case of similar compounds, an analogous but not identical situation results, the pH of the buffered medium being different, depending on the nature of the acetate salt. Thus, typical substances useful in the working of this Invention include the ammonium, potassium and calcium analogues of sodium diacetate. The meat to be coated is preferably substantially dry, by which is meant that no water drips froβ the hung meat. Many meat products are washed with water prior to storage for transport and/or later use and in such cases, it 1s desirable to remove excess superficial water from the meat, for example, by blowing the water from the meat surface. Minimal water on the meat surface provides a better environment for microbial control in that, when the solid material 1s coated thereon, there is produced thereon a very effective concentrated mixture of species: in the case of sodium diacetate there 1s sodium acetate (acting as a buffering agent), acetic add (1n both the molecular and dissociated forms), and sodium diacetate molecules (in the process of dissolution). The natural water content of the meat generally provides sufficient moisture to release acetic acid from the solid material . The solid material may be applied to the meat in any suitable manner, preferably so as to provide a substantially uniform fine coating. For example, electrostatic coating equipment can be adapted to the application of the present dry material to the meat surface. This is a highly satisfactory method. For the best results 1n the case of whole chicken carcass, the geometry of the spraying arrangement is such that the inner cavity of the carcasses receives spray. Alternatively, a dusting box may be used in which the solid material 1s introduced and maintained in suspension during the residence of the meat within the box. The extent of coating may be gauged by any suitable means. An especially suitable apparatus is described 1n co-pending Australian patent application No. PJ3940. An alternative method 1s the measuring of surface pH by using a contact pH measuring device. The solid material should be applied to the surface of the meat to such an extent that on complete liberation of acetic add, there would be liberated from 0.19 to 1.88 mg acetic acid/sq.cm. In the case of sodium diacetate, this means that the sodium diacetate should be applied to the extent that the meat receives froβ 0.5 -5.0 mg solid mater1al/sq cm. Preferably, sodium diacetate should be applied at the rate of from 1-3 mg/sq cm. The solid material applied to the meat may be entirely composed of the acetic acid-releasing substance or it may optionally contain other materials, either inert materials as diluents or materials which alter in some way the properties of the overall material. Typical materials are free-flow agents such as tricalcium phosphate and calcium silicate, water activity reducing agents such as pre-gelled starch and complementary antimicrobial agents such as the sodium, potassium or calcium salts of sorbic or propionlc acid. When materials additional to the acetic acid- releasing substance are used, 1t 1s preferable that the total coating material should be comprised of at least 25% by weight of the substance. It is possible to use less than 25%, but this requires that a very large quantity of material must be applied to achieve the desired effect and this has considerable practical drawbacks. The method provided by the present Invention has numerous advantages over prior art methods used to extend the shelf-life of meat products. In particular, the present method 1s compatible with the further processing of βeat products as currently used such as vacuum and controlled atmosphere packaging. In addition, fie current cost of sodium diacetate, coupled with Its rate of use, makes the method of this invention economically attractive. This 1s particularly so when the simple application technology can be combined with such complementary technologies as specialised packaging systems. Particular advantages of the present method over the dilute acetic add treatment developed by CSIRO mentioned herelnabove Include the greater effectiveness 1n reducing microbiological degradation; it is possible to achieve after several days virtually complete elimination of all microorganisms of enterobacterial origin such as salmonella. Further advantages are the ability to use the method for aarine products where warm water treatment would generally be considered inappropriate and the convenience of application of the method in situations where the transport and use of acetic acid in glacial or solution form would be inconvenient or hazardous, for example in fishing boats. It has also been found that meats treated in accordance with the present method have a more attractive appearance Immediately after treatment than meat cuts treated by alternative processes. The invention is further Illustrated by the following examples which are not to be construed as limiting the scope of the invention in any way. — o — Examp l e 1 This example describes the use of sodium diacetate on beef. Prime cuts of silverside were obtained the day after slaughter. The meat was sliced Into pieces of approximately 1.5 cm thick and of total surface area about 150 sq.ca. These slices were then divided Into three series and treated as described below. Series 1 This was a control series and was left untreated. Series 2 This was treated according to the CSIRO process previously described, that is, 1t was treated by immersion for 10 seconds 1n 1.5% acetic add at 55°C. Series 3 This was treated by lowering the temperature of the meat to 8°C, wiping off excess water and dusting the meat on both sides with sodium diacetate by means of a vibrated sieve of aperture 45 urn, 2 to the extent of about 5 mg/cm . All series were then put 1n standard Stomacher bags and maintained at 8° +_ 1° C. Total plate counts were carried out regularly. It was found that the Series 1 samples had deteriorated to an unacceptable degree 1n less than one week. The Series 2 samples reached this unacceptable level after two weeks. The Series 3 results remained acceptable until more than five weeks had passed. Similar testing on other animal and marine products has shown slallar extensions of shelf life over that obtainable from aethods known to the art. _ n _ Examp l e 2 Use of a method according to the Invention on chickens. Substantially dry chicken carcasses from which all Internal organs had been removed were suspended by the legs and their exterior surfaces sprayed with sodium diacetate by means of electrostatic spray equip entto give a level of about 3 mg/sq cm. The carcasses were stored at 2°C and were subjected to regular microbiological testing, there also being included a number of similar carcasses which had not been sprayed. It was found that the unsprayed carcasses had a shelf life of about 6 days, whereas the sprayed carcasses remained acceptable at 12 days. The tests revealed the presence of salmonella species in all control carcasses and 1n most of the sprayed carcasses. The test was repeated with the alteration that an additional spray was directed Into the body cavities of the carcasses. Testing revealed the same excellent extension of shelf life with the added attraction that salmonella was absent from most of the carcasses - only one carcass in twelve showed the presence of salmonella. Example 3 Use of a method according to the Invention on fish. Substantially dry rockϋng fish fillets obtained commercially were dusted with sodium diacetate from a vibrating 45 um sieve to a level of about 3 mg/sq.cm. These fillets were sealed 1n Stomacher bags as were a number of control (untreated but otherwise similar) fillets. Regular plate counts were taken and these revealed that the control samples had an unacceptable level of microorganisms after 3 days with a standard plate count in excess of 10 counts/g; while after 18 days, the treated fillets standard plate count had still not reached 10 counts/g. Example 4 Use of a method according to the invention on pork. Slices of pork were treated with sodium diacetate from a vibrating 45 um sieve at two rates, about 1 mg/sq cm and about 3 mg/sq cm. These along with similar but untreated controls were kept in commercial polystyrene trays covered with clear plastics film at 2 C and standard plate counts were taken at regular Intervals. The control samples were unacceptable after 11 days whereas the treated meat (1 mg/sq.cm) samples were unacceptable after 21 days and the treated (3 mg/sq.cm.) samples were still microbiologically acceptable after 23 days.

Claims: The Claims defining this Invention are as follows: 1. A method for the treatment of fresh meat such that its shelf-Hfe 1s extended, the method comprising applying to the surface thereof a solid material which will liberate acetic acid in the presence of moisture. 2. A method according to claim 1, wherein the solid material comprises an acetic acid-releasing susbtance selected from complexes of monovalent and divalent acetate salts and acetic acid. 3. A method according to claim 1 or claim 2, wherein the acetic acid-releasing substance 1s sodium diacetate. 4. A method according to any one of claims 1-3 , wherein there is applied to the meat sufficient solid material such that on complete liberation of acetic acid, there will be liberated from 0.19 to 1.88 mg acetic acid/sq.cm. 5. A method according to claim 3, wherein there is applied to meat sufficient sodium diacetate 2 to give a concentration of from 0.5 -5 mg/cm . 6. A method according to claim 5, wherein the 2 concentration 1s from 1-3 mg/cm .' 7. A method according to any one of claims 1-6, wherein the solid material comprises at least one other material in addition to the acetic acid-releasing substance. 8. A method according to any one of claims 1-7, wherein the acetic acid-releasing substance comprises at least 25% by weight of the solid material . 9. A method according to any one of claims 1-8, wherein the surface of the meat is substantially dry at the time of application of the solid material thereto. 10. A solid material adapted to be used to coat the surface of fresh meat so as to increase the shelf-life thereof, wherein the solid material comprises at least 25% by weight of a substance which will liberate acetic acid 1n the presence of moisture. 11. A solid material according to claim 10, wherein the substance is sodium diacetate. 12. A solid material according to claim 10 and claim 11, wherein the solid material comprises at least one other material 1n addition to the acetic acid-releasing substance. 13. A method substantially as described with reference to the examples. 14. A solid material substantially as described with reference to the examples.

Inventors: MOYE CLARENCE JAMES, MOYE, CLARENCE, JAMES
Applicants: MEHECO PTY LTD, MEHECO PROPRIETARY LIMITED
Application year: 1989
Main classification: A23B4
IPC codes: A23B4