Control lipid oxidation in irradiated meat by combining antioxidants.

Ionizing radiation generates hydroxyl radicals in aqueous or oil emulsion systems. Because muscle cells are at least 75% water, irradiation is expected to produce a large amount of hydroxyl radicals and accelerate lipid oxidation in meat. Irradiation also produces hydrogen peroxide under aerobic conditions, which can generate hydroxyl radicals in the presence of ionic iron or heme pigments.

Lipid oxidation has been a significant problem in irradiated meat only when meat was irradiated and stored under aerobic conditions. Researchers at Iowa State University found that combining different antioxidants could prevent lipid oxidation in aerobically packaged irradiated meats during storage.

Many antioxidants can prevent lipid oxidation in irradiated meat. However, if you want to avoid synthetic antioxidants such as BHA, BHT and propyl gallate and are looking for the antioxidants from natural sources, then sesamol and gallic acid are among the best. Especially when they are combined with tocopherol, they can minimize color problems in addition to lipid oxidation in irradiated light meats, such as poultry breast and pork. A combination of tocopherol and ascorbic acid is excellent for maintaining fresh beef color as well as oxidative stability of irradiated ground beef.

Scientists found that supplementing the diets of turkeys with 200 IU of tocopherol per kg or more was effective in minimizing oxidative changes in irradiated raw turkey breast and thigh meats when they were stored under aerobic conditions. The antioxidant effect of dietary tocopherol was not strong enough to control lipid oxidation in cooked meat stored under aerobic conditions. However, vitamin E played an important role in the quality of the cooked meat because vitamin E was a highly efficient antioxidant in maintaining low baseline lipid peroxidation levels in irradiated raw meat.

Adding tocopherol, gallate and sesamol individually or in combinations created significant antioxidant activities in irradiated raw turkey, pork and ground beef even under aerobic conditions. As the storage time increased, the extent of lipid oxidation also increased. The rate of lipid oxidation was faster in irradiated than in nonirradiated meat. However, combinations of gallate, tocopherol and sesamol-tocopherol had very strong antioxidant effects in stored irradiated meat.

Further information. Dong Ahn, Department of Animal Science, Iowa State University, 2276 Kildee Hall, Ames, IA 50010; phone: [phone]; fax: [phone]; email: [e-mail].