Improving the quality and value of muscle foods is a major objective of the meat industry.
The physicochemical properties of comminuted meat system are essential to final product quality and consumer acceptability (Smith, 1988; Barbut and Mittal, 1989). The physicochemical state of the myofibrillar proteins, myosin and actomyosin, confer functionality to meat systems and thereby have a direct role in determining the quality and value of processed meat (Yasui et al., 1982; Camou and Sebranek, 1991).
Among the problems affecting the economic value of muscle foods are the inferior quality of PSE meat and the surplus of MDTM. The Pork Chain Quality Audit suggested that in their study "10.2% of the carcasses were classified as having PSE muscle" (Cannon et al., 1996). PSE discounts $0.35/head thus, the economic loss on the pork industry is nearly $32 million/yr (ibid). This devaluation is due, in part, to the shrinkage of meat and the loss of weight during storage (Hedrick et al., 1994a). Research indicates that the loss of protein functionality in PSE is responsible for the inferior quality of PSE meat (Boles et al., 1992). On the other hand, MDTM is a low cost, underutilized by-product of fresh meat processing with high nutritive value and protein functionality. MDTM is approved for use in commercially processed meat products. However, the high proportion of fat and collagen in MDTM and subsequent high rate of lipid oxidation make it a low value raw material to meat processors (Field, 1981; Yang and Froning, 1992; Lee et al., 1975). It has been suggested that PSE meat could be used with special formulations that contain ingredients or conditions to restore meat quality and protein functionality thereby reducing yield losses and improving texture (Kelleher and Hultin, 2000). Addition of various food-grade proteins to meat systems to increase total functional protein content has been proved to have a positive contribution to the structural properties (firmness, gelation, and meat binding) of meat products (Pfaff, 1989; Li et al., 1998; Boles et al., 2000). However, results of these investigations demonstrated that, no single non-meat protein constituent was capable of enhancing all of the physicochemical properties of meat systems to the same extent as actomyosin.
Thermally induced meat protein gelation is the key element required to bind meat pieces together with optimal strength in processed meat products (Hedrick et al, 1994b). Heat-induced gelation of the meat proteins, myosin and actomyosin, plays an essential role in the development of binding properties of comminuted meat products such as sausages (Samejima et al., 1969; Ishioroshi et al., 1983). Thus, myosin and actomyosin are the most important factors for the development of the binding properties of thermally induced meat protein gels (Samejima et al., 1969; Samejima, et al., 1981 and 1982). Not only do myosin and actomyosin contribute to the rigidity (firmness) of thermally induced meat gels, they are also critical to the water holding capacity (WHC) and high cooking yields of comminuted meat products such as sausages (Hamann, 1988; Smith, 1988). Heating transforms the meat sol to a gel resulting in the formation of a three-dimensional network (Samejima et al., 1969; Acton et al., 1981; Yamamoto et al., 1988). The protein network physically and chemically enhances the water retention by their capillarity and non-covalent bonding (Acton and Dick, 1984). Water retention in processed meat products is the major contributing factor to the sensation of juiciness (Hedrick et al., 1994c). Cooking loss directly impacts both economic and palatable value of processed meats. The greater the amount of moisture retained during processing the greater the value of the product. The loss of weight of processed meat products during processing is a function of the water holding ca pacity. However, PSE meat has tremendously reduced palatability of meat due to higher moisture losses during cooking.
The objective of this research was to employ myosin/actomyosin extracted from MDTM as an ingredient to improve physicochemical properties of processed PSE meat products.