Lipid oxidation and production of off-odor in irradiated meat

Abstract

Emulsion-type raw and cooked pork sausage with different fat content or fatty acids was prepared to determine the effect of irradiation on lipid and cholesterol oxidation, color changes, and volatile production during storage. Lipid oxidation increased with the increase of fat content or irradiation dose in both raw and cooked pork products. Irradiated batters had higher cholesterol oxide content than non-irradiated, and the major cholesterol oxides formed in raw irradiated pork batters were 7aand 7P-hydroxycholesterol. Hunter aand b-values of both raw and cooked pork products in aerobic packaging decreased with irradiation regardless of fat content. In vacuum packaging, however, irradiated cooked pork sausage had higher Hunter a-values than nonirradiated. Irradiation significantly increased the amount of 1-heptene, 1-nonene, and total volatile compounds in raw and cooked pork sausage. The amounts of 1-heptene and 1-nonene were not associated with TEARS values of pork sausage but were closely related to irradiation dose. In both irradiated and nonirradiated pork sausage, aerobic packaging produced more volatile compounds during storage than did vacuum packaging. The production of aldehydes, ketones, and alcohols in aerobic-packaged pork sausage were not influenced by irradiation at 0-day storage. However, irradiation accelerated lipid oxidation and increased the amounts of aldehydes, ketones, and alcohols during storage. The TEARS of aerobicor vacuum-packaged sausage prepared with lard were higher (p<0.05) than the sausage prepared with flaxseed oil likely a result of the high tocopherol content in flaxseed oil. To investigate the distinction between volatile compounds related to oxidized flavor and irradiation odor, and to understand the mechanisms of off-odor production in irradiated meat on a chemical basis, oil emulsions containing amino acids or proteins were analyzed.