In the present study the effects on shelf life and sensory acceptance of gamma-irradiated refrigerated poultry breast fillets subjected to modified atmosphere packaging (80% CO2/20% N2 or vacuum) were investigated. After irradiation with 2 kGy, sensory acceptance tests and monitoring of bacterial growth were performed in order to determine the sanitary quality of the samples. It has been found that irradiation, used in combination with modified atmosphere packaging, can double the shelf life of refrigerated poultry breast fillets by reducing the populations of aerobic mesophilic and psychrotrophic bacteria, enterobacteria, coliforms, Listeria spp. and Aeromonas spp., without significantly modifying its color or its overall appearance, the lactic acid bacteria being the most resistant to exposure to radiation and carbon dioxide.

This work investigated the effects of different packaging methods (air and vacuum) combined with irradiation (0.0, 2.0 and 3.0 kGy) on the preservation of chicken breast fillets stored at 1ºC for up to 18 days by sensorial test, determination of pH and bacterial growth. The findings indicated that the post-irradiation lag phase increased with the dose, leading to an extension in shelf-life. Vacuum-packed samples irradiated at 3.0 kGy exhibited the longest shelf life. Among the analyzed bacteria, coliforms and Listeria spp. were most sensitive to gamma radiation. All the fillets acquired more attractive coloration and better overall impression with irradiation. The combined use of vacuum packaging and irradiation (3.0 kGy) reduced the microbial populations without causing change in pH and yielded a significant shelf-life extension of refrigerated fillets, besides improving its appearance.

Foram analisadas 30 amostras de carne bovina moída resfriada, previamente embaladas, provenientes de estabelecimentos comercias do município de Niterói, RJ, com o objetivo de se observar a freqüência de bactérias do gênero Listeria spp. Utilizou-se para isto a metodologia revisada do USDA. 50% das amostras analisadas apresentaram contaminação por Listeria spp., sendo a L. innocua (SEELIGER & SCHOOFS, 1979) a espécie isolada em maior número, seguida pela L. monocytogenes (MURRAY et al., 1926; PIRIE, 1940). Na tipificação sorológica, observou-se maior prevalência de L. monocytogenes pertencente ao sorotipo 4b (50%), porém o sorotipo ½ c também foi identificado. As amostras que apresentaram-se contaminadas com L. monocytogenes, caracterizam-se como potencialmente capazes de ocasionar enfermidades transmitidas por alimentos.

Thirty bovine ground meat samples from several markets from Niterói, RJ, were analyzed, in order to observe the frequency of bacterias of the genus Listeria spp. A USDA revised methodology as applied in this research. Fifty percent of the samples were contaminated by Listeria spp.. L. innocua species as the most isolated, followed by L. monocytogenes. In serological typification, the greatest prevalence was that of sorotype 4b L. monocytogenes (50%), however the ½ c sorotype was also identified. Samples contaminated by L. monocytogenes are potentially capable of causing diseases through food consumption.