Abstract: Semitendinous muscles (n = 8) obtained from Chinese Yellow Cattle were irradiated at 0, 1.13, 2.09, or 3.17 kGy using a 60Co irradiation source and then stored at 7 ℃ for 10 days to estimate beef fatty acid composition and quality changes with different gamma irradiation doses and storage time. Contents of polyunsaturated fatty acid (PUFA), n-3 PUFA and n-6 PUFA, as well as P/S decrease after irradiation, without abvious changes during 10 days of storage. Purge loss and TBARS increase with irradiation dose increasing from 0 to 3.17 kGy just after irradiation for 0 day. However, after 10 days of storage, purge loss and TBARS value decrease with irradiation dose increasing, and samples have the lowest purge loss and TBARS value at the dose of 3.17 kGy. Total bacterial counts decrease significantly after irradiation, and the reduction of total bacterial counts is propor-tional with irradiation dose increasing. It can be concluded that beef fatty acid percentages and compositions, change for irradiation .However, no great changes occur with irradiation dose increasing from 1.13 to 3.17 kGy within 10 days of storage. Low dose of 3 kGy gamma irradiation is recommended to apply in fresh beef before storage.

Key words: radiation, beef, fatty acid, TBARS, total bacterial counts