46G-13 |
Nitric oxide synthase activity in muscle food |
R. G. BRANNAN and E. A. Decker. Department of Food Science, University of Massachusetts, Amherst, MA 01003 Nitric oxide is enzymatically produced in animals by nitric oxide synthase (NOS). NOS catalyzes the oxidation of arginine to produce nitric oxide and citrulline. Nitric oxide can react with superoxide to form peroxynitrite. Since exogenous peroxynitrite has been shown to induce the formation of lipid hydroperoxides in skeletal muscle microsomes and homogenate, peroxynitrite-induced lipid oxidation in post-mortem muscle will be dependent on nitric oxide production. The objective of this research was to investigate the potential for nitric oxide production in skeletal muscle by characterizing the activity of NOS in post-mortem tissue from several muscle food species. The effect of extrinsic conditions commonly encountered in post-mortem muscle foods such as pH, salting, thermal processing, freeze/thaw stability, and refrigerated storage was investigated. NOS activity was determined in minced muscle by monitoring the conversion of radiolabeled arginine to citrulline using a commercially available NOS assay kit. The incubation buffer of the NOS assay kit was adjusted to obtain the desired pH’s and NaCl concentrations. For thermal processing, freeze/thaw stability, and refrigerated storage experiments, minced chicken muscle was subjected to these treatments before the NOS assay was performed. Fresh muscle from all species tested exhibited NOS activity. Chicken dark muscle NOS activity was: 1) completely lost after 24 h of refrigerated storage; 2) not affected by pH (4.5-7.4); 3) inhibited by NaCl (1–2%); and 4) stimulated at internal cooking temperatures up to 55 C but completely inhibited at higher temperatures. Results of this study indicate that post-mortem NOS in chicken dark muscle is active within the first day of post-mortem storage. Since superoxide is likely to be produced during the cessation of aerobic metabolism, the potential may exist for the formation of peroxynitrite and consequently, lipid hydroperoxides during the early post-mortem period.
Session 46G, Muscle Foods I
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