IRRADIATION AND POSTIRRADIATION STORAGE AT 2+ -2-DEGREES-C OF TILAPIA(TILAPIA-NILOTICA X ILAPIA-AUREA) AND SPANISH MACKEREL (SCOMBEROMORUSCOMMERSON) - SENSORY AND MICROBIAL ASSESSMENT/

Tilapia (low-fat farm fish, Tilapia nilotica x T. aurea) and Spanish m ackerel (high-fat seawater fish, Scomberomorus commerson) were subject ed to gamma irradiation doses of 1.5, 3.0, 4.5, 6.0, and 10.0 kGy by u sing a semicommercial gamma irradiator. The irradiated and unirradiate d (controls) fish were stored at 2 +/- 2 degrees C and samples were dr awn at day 0, 4, 8, 12, 16, and 20 for sensory evaluation and microbio logical analysis. Doses of 3.0 and/or 4.5 kGy extended the sensory acc eptability (appearance, odor, texture, taste) and the microbial qualit y (total count and coliforms) by 8 days compared to the unirradiated c ontrols. Hydrogen sulfide-producing bacteria were low in both types of fish and a dose of 1.5 kGy kept this flora at low levels throughout t he storage period. Moreover, this dose level was also sufficient to el iminate Salmonella spp. from both fish. Yersinia and Campylobacter spe cies were effectively eliminated by doses of 1.5 and 3.0 kGy. Doses of 6.0 and 10.0 kGy caused a reduction in psychrotrophic counts but were detrimental to the quality of both species of fish.