Color problems of restructured meat products, especially beef products, are a major problem for manufacturers.
Undesirable colors cause reduced acceptability, especially of restructured steaks, because after price, color is the single most important factor considered by the consumer when selecting meat. Hood and Riordan (1973) reported a linear increase in discrimination by consumers against discolored meat as the percentage of metmyoglobin increased in fresh beef. Booren and Mandigo (1981) stated that producing a restructured steak with acceptable color involves no secrets-only a thorough understanding of factors affecting meat color, particularly during processing. A high degree of control is necessary for each of the numerous steps of processing restructured meat products. This is even more difficult in a commercial production plant than in a pilot plant or the product development laboratory.
The restructuring process, which includes particle reduction, mixing, forming and frequently freezing and tempering, creates conditions that favor chemical and physical changes in meat and its pigments. The oxidative chemical changes cause discoloration problems that limit retail acceptance of restructured meats-unless they are masked by battering and breading, pre-cooking, curing or other means. These color defects also may affect institutional acceptance if they are so severe to catalyze lipid oxidation or other aroma and flavor deterioration.
To overcome discoloration in restructured products, processors must integrate the combined effects of raw material temperature and quality; processing variables, equipment and conditions; and ingredient functionality on final product appearance. Processors must develop a new awareness regarding raw material condition, with special emphasis on maintaining high metmyoglobin-reducing activity, minimizing raw material exposure to oxygen, holding and processing meat at a low temperature, and concern about microbiological deterioration.
The effects of these factors, as well as the advantages and disadvantages of meat from hot-boned or electrically stimulated carcasses, need careful study.
Processing under conditions that minimize oxygen incorporation, or at least remove oxygen from meat mixes, may be essential and should be studied. Strict control of temperature and minimizing the time at certain temperatures are critical to solving color problems. Freezing and tempering are necessary for some restructuring processes, but product temperatures between 12 degrees C and -2 degrees C have serious detrimental effects on product color.
Ingredients
More work is needed on methods for minimizing the required ingredients that encourage discoloration but may have other essential functions. Ingredients that add reducing equivalents may be beneficial. Non-frozen restructured product technology, involving the incorporation of functional agents such as gums and collagen, needs to be evaluated for its effects on appearance.
In restructured meat, the level of added salt has significant effects on product color. Although meat with salt levels below 1 percent may have improved color scores compared with meat with higher levels (Schwartz and Mandigo 1976; Huffman et al. 1981A), the presence of any level of salt, especially at concentrations of 1.5 percent or higher, decreases color desirability in pork (Schwartz and Mandigo 1976; Huffman and Cordray 1979; Huffman et al. 1981B; Marriott et al. 1983), in beef (Ockerman and Organisciak 1979; Vimini et al. 1983; Huffman et al. 1984A) and in lamb (Brewer et al. 1984.)
Several beneficial effects of adding phosphates to restructured meat products, including changes in pH and ionic strength, chelation of metal ions, and structural interactions with myofibrillar proteins, are well established. Restructured beef and pork containing phosphates (usually tripolyphosphate) up to 0.5 percent have improved color scores and stability compared with formulations without phosphate (Schwartz and Mandigo 1976; Huffman and Cordray 1979; Huffman et al. 1981A).
Phosphate levels above 0.3 percent often create detectable flavor problems. A phosphate level of 0.125 percent in restructured products has been recommended by Mandigo (1980).
Rhee (et al. 1983) reported that certain non-meat additives decreased product oxidation when added to meats. For example, 3 percent glandless cottonseed flour in ground beef reduced TBA values and discoloration, especially at salt levels of 1 percent or less.
The incorporation of non-meat extenders that have antioxidant properties may have potential in reducing restructured meat color problems.
Since restructured meat products are susceptible to both pigment and lipid oxidative changes, the incorporation of reducing agents seems attractive.