The terms "pale, soft and exudative" are terms of the art generally understood as referring to certain undesirable characteristics of cuts or chunks of fresh meat. The terms relate to a preference evaluation and do not denote or suggest that such meat is less wholesome, inedible or unusable. Meat which is developing or has developed pale, soft and exudative characteristics may be termed PSE meat. Another category of meat is that which has dark, firm and dry or non-exudative characteristics, which can be described as DFD meat. The term "normal" meat as used herein refers to meat which is acceptable in a preference selection and whose characteristics are subjectively generally between PSE meat and DFD meat.
The pale characteristic refers to a reduction in color intensity of ground meat or of a fresh cut or chunk of meat. A chunk of meat can be defined as a fresh cut of meat which has been subdivided into pieces having a dimension of about 1 inch or more. For example, when the fresh meat cut is ham, good color intensity is one wherein the ham has a darkish pink-to-red color. In contrast, a pale ham is one that has a dull and light grayish coloration. Generally speaking, a so-called pale ham is less desirable and is of a lower commercial value than a ham having a more intense coloration. A cut or chunk of meat exhibiting a soft texture is one that is not particularly firm. This condition expresses itself in finished pieces of meat, for example, hams, as a quality which makes it difficult to cut such meat into thin slices. The exudative quality refers to the inability of cuts or chunks of meat to hold water.
A pale, soft and exudative (PSE) muscle cut or chunk or grind of meat is thus one which has a pale color, soft texture and a reduced capacity for holding water. A cut or chunk or grind of meat which does not have PSE characteristics has a noticeably darker color and a firmer texture because the muscle protein is less denatured than in a PSE muscle. A muscle cut or chunk or grind which does not exhibit noticeable PSE characteristics also has a greater water holding capacity so that the moisture remains within the meat, even when cut or sliced, rather than exude therefrom over the passage of time.
A suggested reason for the occurrence of pale, soft and exudative characteristics is that lactic acid is rapidly generated post-mortem in the carcass. The lactic acid is believed to accumulate within the meat components and rapidly lower the pH of such meat. This fast lactic acid generation and fast pH lowering is believed to cause or at least contribute to the damaging or denaturing of muscle protein, thereby resulting in the appearance or occurrence of the PSE condition.
A number of approaches have been described in the art to prevent the development of the PSE condition. Exemplary references include U.S. Pat. Nos. 4,190,100 and 4,551,338 to Wallace; Borchet et al., "Prevention of Pale, Soft Exudative Porcine Muscle Through Partial Freezing with Liquid Nitrogen Post-Mortem", J. Food Science 29 (2): 203-209 (1964); and E. J. Briskey, "Etiological Status and Associated Studies of Pale, Soft, Exudative Porcine Musculature", Adv. Food Research, 13: 159-167 (1964). More recently, U.S. Pat. No. 5,085,615 to Gundlach et al. described the use of solid carbon dioxide to reduce the development of PSE characteristics in freshly killed meat.
While the above cited-art describes various methods of preventing the development of PSE characteristics in meat, none of them describe a procedure for lessening, reversing or repairing the effects of PSE once it has occurred. That is, the art does not describe a process whereby meat cuts or chunks or grinds which have developed or begun to develop PSE characteristics may be treated to lessen, reverse or repair the PSE process or the effects of the PSE process such that the quality of pale, soft and exudative (PSE) meat improves and becomes more nearly like those of normal meat.
A number of patents or publications teach the use of the enzyme transglutaminase (hereafter TG), also known as glutamate transaminase, to improve the water retention and texture of fish, fowl and animal meats, particularly ground or minced meats, soybean protein, egg albumin and casein containing products. However, none of these patents or publications teach the use of TG to lessen, reverse or repair the PSE condition in meat, or to improve the cohesiveness and firmness of meat products which exhibit the PSE condition or PSE characteristics. Furthermore, none of these patents or publications teach the use of TG to further improve the quality of chunks of normal meat or fowl, or to further improve the cohesiveness and firmness of products manufactured from normal meat or fowl relative to products manufactured without the use of TG.
For example, U.S. Pat. No. 4,917,904 to Wakameda et al. describes a process whereby TG is added to various meats, soybean protein, egg albumin or casein-containing mixtures to improve the texture thereof. Specifically, Wakameda et al. describe adding TG to ground fish meat, minced fish meat, fillet and lyophilized fish powder, ground or minced animal meat, and fowl and block meat to improve the water retention of the final ground or minced meat product. However, Wakameda et al. state that while TG enhances the water retention in such animal meat and fowl, the texture thereof becomes hard to masticate or chew. This difficulty in chewing the product is an undesirable property. Wakameda et al. do not teach the use of TG to lessen, reverse or repair the PSE condition or the effects of the PSE condition.
Examples of publications discussing TG effects include "Transglutaminase Mediated Polymerization of Crude Actomyosin Refined From Mechanically Deboned Poultry Meat", Akamittath and Ball, Journal of Muscle Foods 3, 1992, 1-14; and "Strength of Protein Gels Prepared With Microbial Transglutaminase as Related to Reaction Conditions", Sakamoto, Kumazawa and Motoki, Journal of Food Science, Volume 59, No. 4, 1994.
European published patent application 0 333 528 describes the genetic alteration of micro-organisms to produce TG and the addition of such genetically altered micro-organisms to ground meats to improve the texture of the ground meat when it is cooked. Generally, the genetically altered micro-organisms are described as being used with ground beef, soya, and casein, among other substances, to prepare ground meat products, sausages and cheeses. This publication does not teach the use of the TG-producing micro-organisms to lessen, reverse or repair the PSE condition or the effects of the PSE condition.
Japanese patent publications describing the use of TG are No. 06261692A (preparation of animal feeds by allowing TG to act upon the meat of animals, fish and/or their by-products which are used as such feeds); No. 6225729A (addition of TG to ground fish or cattle meat); No. 6197738A (addition of TG to ground meat for making hamburgers); No. 6113796A (addition of TG to paste food for making sausages or hamburgers of fish meats); No. 6090710A (using thrombin in combination with plasma protein, fibrinogen concentrate, fibrinogen or transglutaminase plasma); No. 5207864A (use of transglutaminase to improve meat color); No. 3210144A (use of transglutaminase with canned, or potted meat, fish, crab and scallop products); No. 2255060A (adding transglutaminase to minced meat or fish paste products); No. 2100655A (addition of transglutaminase to ground fish meat); and No. 2100654A (addition of transglutaminase to ground `okiama` (Euphausia superba) fish to improve the water retention and smoothness of the finished ground product). Additional Japanese patent publications describing the use of transglutaminase are Nos. 2100653A, 2100651A, 2086748A and 2079956A, all of which describe the use of transglutaminase with ground fish or meat pastes.
While TG has been described in the above cited art as improving selected characteristics of ground meat products and some non-meat, protein-containing products, this art does not describe the use of TG to lessen, repair or reverse the PSE condition or the effects of PSE on whole cuts or chunks of meat.
Accordingly, it is a general object of the present invention to provide a procedure for lessening, reversing or repairing the PSE condition or the effects of PSE in meat and/or meat products.
Another object of the present invention is to provide a process for lessening, reversing or repairing the PSE condition or the effects of the PSE condition in whole cuts or chunks of fowl and porcine muscle and/or products manufactured from such chunks of fowl and pork.
Another object of the invention is to provide a process for lessening, reversing or repairing the PSE condition or the effects of PSE in whole cuts or chunks of porcine muscle, turkey breast and chicken breast, and products manufactured using such chunks of pork, turkey breast and chicken breast.
Another object of the invention is to provide a process for lessening, reversing or repairing the PSE condition or the effects of PSE in smoked or unsmoked porcine muscle, turkey breast and chicken breast, and products manufactured using same.
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