Stability of catalase and its role in lipid oxidation in beef muscle

Abstract

When ground beef muscle (semimembranosus, SM) was aerobically refrigerated for 6 days with or without the addition of exogenous purified catalase (from bovine liver), there was no decline in catalase activity during storage. The additional catalase lowered lipid oxidation (as measured by 2-thiobarbituric acid-reactive substances, TBARS) about 8% in the 6 days of storage. When 3-aniino-1,2,4-triazole (2.5%), a catalase inhibitor, was added to ground beef SM, lipid oxidation (peroxide values) was also inhibited. This effect was attributed to the antioxidative compounds that could be formed via Maillard reaction between the added inhibitor (having an amino group) and carbonyl compounds in the meat samples. When another catalase inhibitor, sodium azide, was used instead, the peroxide values of the treated samples were more than 40% higher than those of untreated samples during 4 days of aerobic storage at 4'C. When ground beef SM was washed repeatedly, as in processing for surimi or in preparation of the muscle fiber matrix containing the membranal lipids in many studies conducted on meat lipid oxidation mechanisms, a significant loss (58-64% on a wet weight basis) of catalase activity occurred, presumably due to the dissolution of catalase into the wash water. Catalase activity in ground beef SM, beef longissimus dorsi (LD), chicken breast (B), chicken thigh (T), and pork LD muscle samples did not decline during 3 months of storage at-20'C, even when subjected to 3 freeze-thaw cycles. TBARS in all samples except chicken B, showed some increase during this storage period. However, TBARS accumulation in stored samples was not affected by the freeze-thaw treatment. Beef SM and LD tended to be higher in initial TBARS level, as well as the rate of TBARS increase from the initial levels, than the other species/muscle combinations evaluated. Catalase is fairly stable in muscle tissue. Catalase activity in muscle tissue is not likely to decrease during the normal periods of storage under refrigerated or frozen conditions. In frozen storage, even freeze-thawing would not affect endogenous catalase. Washing, however, markedly lowers catalase activity. This indicates that catalase probably contributes significantly to the antioxidant process in uncooked meat.