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D. PARK1, Y. L. Xiong1, A. L. Alderton1, and T. Ooizumi2. (1) Dept. of Animal Sciences, Univ. of Kentucky, Lexington, KY 40546, (2) Dept. of Marine Bioscience, Fukui Prefectual Univ., Obama, 917-0003, Japan Degree of oxidation is one of the major indicators of meat quality deterioration. Meats and meat products are commonly subjected and susceptible to oxidizing conditions during processing and storage. In our study, biochemical changes in myofibrillar protein isolate (MPI) exposed to three common oxidizing matrixes present in muscle foods were investigated. MPI was prepared from pork Serratus ventralis muscle collected from 10 Boston shoulders within 4 days postmortem. MPI suspensions (30 mg protein/mL) in 15 mM piperazine-N,N bis(2-ethane sulfonic acid (PIPES) buffer (pH 6.0) were oxidized with hydroxyl radical-generating systems (HRGS, 0.01 mM FeCl3, 0.1 mM ascorbic acid, 0.0-5.0 mM H2O2), oxidizing lipids (0.0-5.0 mM linoleic acid, 3750 units of lipoxidase/mL), or metmyoglobin oxidizing systems (0.0-0.5 mM) for 24 h at 4º C. Changes in oxidized MPI were measured by determining Ca- and K-ATPase activity, protein carbonyls, 2-thiobarbituric acid-reactive substances (TBARS), and peroxide value (PV). Differences between treatments were evaluated statistically by Student Newman Keuls (SNK) method. Calcium-ATPase activity ranged from 0.56 to 1.45 mM phosphate/mg protein/10 min in all treatments, while K-ATPase activity ranged from 0.01 to 0.31 of the same unit (P < 0.05). On average, carbonyl content in metmyoglobin oxidizing systems was the highest; whereas TBARS content was the highest in HRGS (P < 0.05). The PV, however, was barely detectable indicating low levels of peroxide formed and/or low sensitivity of the method. The biochemical changes were matrix- and dose-dependent. In general, at low intensities of prooxidants, the changes were non-linear and abrupt, but became linear at higher doses. The results from this study illustrated that biochemical changes in oxidized myofibrillar protein isolate were distinctive of the specific oxidizing systems. This research offered an improved understanding of the mechanisms of protein and lipid oxidation in meat products.
Session 68, Muscle Foods: Biochemistry, color and non-meat ingredients
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |