Influence of gamma irradiation (1.5-10 kGy) and post-irradiation storage up to 20 days at 2 ‫ע‬ 2ЊC on some chemical criteria of tilapia and Spanish mackerel were studied. Total volatile basic nitrogen formation was lower in irradiated fish than in the unirradiated. Irradiation also caused a larger increase in thiobarbituric acid values which continued gradually during storage. Some fatty acids decreased by irradiation treatments at all doses. Thiamin loss was more severe at higher doses (≥4.5 kGy), whereas riboflavin was not affected. Alpha and gamma tocopherols of tilapia and alpha, beta, gamma, and delta tocopherols, in Spanish mackerel, decreased with increased dose and continued to decrease during 20-day post-irradiation storage.

Chickens were subjected to gamma irradiation doses of 2.5, 5.0,7.5, and 10.0 kGy using a semi-commercial gamma irradiation facility. The irradiated and unirradiated (control) chickens were stored at 4.0°C, and samples were drawn at day 0 and at 3-day intervals up to 21 days for sensory and microbiological analyses. All irradiation doses (2.5 to 10.0 kGy) had little effect on the sensory acceptability (appearance, odor, texture, taste) of both raw and cooked chicken (breast and thigh). Irradiation extended the time during which these characteristics were acceptable. Moreover, juiciness and tenderness of cooked chicken were only slightly affected by irradiation, and chickens were not rejected even after 21 days of storage. A dose of 2.5 kGy seemed adequate to extend the shelf life of chicken by 12 days, and increasing the dose level above 2.5 kGy gave little if any additional benefit as far as total and psychrotrophic bacterial counts are concerned. Moreover, the dose of 2.5 kGy was enough to destroy Salmonella, Yersinia, and Campylobacter species and coliforms. The study also showed that yeasts of the genera Candida, Saccharomyces, and Alternaria started to grow on day 12 in samples treated with ≥5.0 kGy, but not in samples treated with <5.0 kGy.

No abstract

Tilapia (low-fat farm fish, Tilapia nilotica × T. aurea) and Spanish mackerel (high-fat seawater fish, Scomberomorus commerson) were subjected to gamma irradiation doses of 1.5, 3.0, 4.5, 6.0, and 10.0 kGy by using a semicommercial gamma irradiator. The irradiated and unirradiated (controls) fish were stored at 2 ± 2°C and samples were drawn at day 0, 4, 8, 12, 16, and 20 for sensory evaluation and microbiological analysis. Doses of 3.0 and/or 4.5 kGy extended the sensory acceptability (appearance, odor, texture, taste) and the microbial quality (total count and coliforms) by 8 days compared to the unirradiated controls. 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 the storage period. Moreover, this dose level was also sufficient to eliminate Salmonella spp. from both fish. Yersinia and Campylobacter species 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.