Influence of ionizing radiation (60Co) on the physical-chemical, microbiological and sensory keeping quality characteristics of raw chiken thigh and chiken breast fillets packed in different packaging systems. / Influencia da radiação ionizante (60Co) na manutenção da qualidade fisico-quimica, microbiologica e sensorial de cortes de coxa e file de peito de frango acondicionado em deiferentes sistemas de embalagens.

Luciana Miyagusku

Samples of raw chicken thigh and chicken breast fillets previously packed in different packaging systems [wrapped in high oxygen-permeable film (AIR), vacuum packed (VC) and CO2 and N2 modified-atmosphere-packed (MA)] were submitted to ionizing radiation delivered by a 60Co unit. A series of physical-chemical, microbiological and sensory parameters were evaluated to assess the effect of the radiation process on the shelf-life and keeping quality of chicken cut samples exposed to radiation and subsequently cold-stored at 5±1ºC for 39 days (AIR) and 3 months (VC and MA). The results of instrumental color assessment trials showed that the radiation treatments investigated in this study did not cause any color changes in any of the radiation-treated chicken cuts. On the other hand, lipid oxidation - measured using the TBARS (thiobarbituric acid reactive substances) content as indicator ? exhibited a gradual increase proportional to the increase of the radiation dose. The pH values of the chicken thigh/AIR, VC and MA and chicken breast/AIR, VC and MA control samples did not exhibit any significant differences throughout the storage period investigated. Irradiation of the chicken meat samples packaged in high oxygen-permeable film (chicken thigh/AIR and chicken breast/AIR) and in barrier film (chicken thigh/VC, chicken breast/VC, chicken thigh/MA and chicken breast/MA) resulted in a considerable reduction of E.coli, Pseudomonas spp and total enterobacteria counts, however, lactic acid bacteria, yeasts and moulds demonstrated higher resistance in the AIR packaging system. In the samples packaged in barrier film (vacuum and modified atmospere) the lactic acid bacteria were identified as the most resistant to radiation. None of the samples showed growth of Brochothrix thermosphacta and Listeria monocytogenes throughout the storage period investigated. The results of chromatographic analyses of substances generated by lipid degradation showed similar compound profiles for the samples submitted to the three atmosphere conditions studied. In addition, no migration of substances from the packaging material to the meat samples was detected. Irrespective of the packaging system, increasing the radiation dose to levels above 3kGy resulted in the development of a burnt odor the intensity of which increased with increasing dose values, thereby indicating 3kGy to be a recommendable limit that ensures a product with a long shelf-life and without sensory perceptible changes. While the shelf-life of the control samples of chicken thigh/AIR and chicken breast/AIR was estimated at 5 days, irradiation with increasing doses of 1,5 to 7,0 kGy was found to result in a 1,8 to 7,4-fold increase in the shelf-life, respectively. The irradiation process demonstrated to be a potentially very useful tool to extend the shelf-life and improve the quality of chicken cuts.

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