Effect of pH and Temperature on Myoglobin in Fresh Meat
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Animal Sciences Honors Theses; 2008
Color or appearance of a food product is one of the most important attributes that influences consumers’ purchasing decisions. In living muscle tissue, the function of myoglobin is to bind and store oxygen; however, in meat products the concentration and chemical state of this water-soluble protein influences the visual color of meat. Denaturation of myoglobin can result in less desirable appearance and may be associated with other undesirable palatability characteristics in fresh pork, such as Pale Soft Exudative (PSE) pork, which is one of the largest economic burdens to the pork industry. The characteristics of PSE include undesirable color, soft texture, and excessive purge. Pork carcasses that produce PSE product often have an accelerated rate of post-mortem metabolism, which can produce a combination of high temperature and low pH in muscle tissue. The purpose of this study is to determine the effects of specific pH and temperature combinations on the denaturation of porcine myoglobin, mimicking the range of potential environments of postmortem metabolism. Bovine myoglobin was isolated and purified from a fresh beef heart. The myoglobin was reconstituted and subjected to multiple pH levels (ranging from 7.0 to 5.4 in increments of 0.4 pH units). The stability of myoglobin was evaluated at each pH level from 36° C to 44°C in 4°C increments. Samples of myoglobin were evaluated within each of the 15 pH and temperature combinations. Myoglobin fractions were evaluated using spectrophotometry to determine the extent of myoglobin dentauration within each pH and temperature combination. The major finding from this project is that myoglobin is not significantly altered or damaged from the pH and temperature combinations within the physiological range of postmortem metabolism. The combination of high temperature and low pH did not significantly affect the function of myoglobin. The changes in percent oxymyoglobin were not to the extent that would explain the pale color observed in PSE pork.
College of Food, Agricultural and Environmental Sciences