Nitric oxide synthase activity in muscle foods

Nitric oxide is enzymatically produced in animals by nitric oxide synthase (NOS). Nitric oxide reacts with superoxide to form peroxynitrite, which initiates oxidative reactions. To assess the potential for nitric oxide formation in muscle, NOS activity was determined in fresh muscle (<8 h post-mortem) from several species under conditions expected in muscle foods. Fresh muscle from all species exhibited NOS activity. NOS activity in muscle was reduced during refrigerated storage. Chicken thigh muscle NOS activity was not affected by pH over the range of 4.5–7.4, but was inhibited by 1 and 2% NaCl. Chicken thigh muscle NOS activity was stimulated at internal cooking temperatures up to 55 °C but was completely inhibited at higher temperatures. Results of this study indicate that post-mortem NOS is only active for the first several days of post-mortem storage.