Effect of hurdle technology, chitosan and gamma radiation on quality parameters of chicken fry

Abstract

The study on the effect of low dose gamma radiation and chitosan coating on shelf-life and quality changes of ready-to-eat chicken fry under vacuum packaging was conducted in the Department of Livestock Products Technology, Mannuthy. Half of the prepared chicken fry was coated with 0.5 per cent chitosan in one per cent glacial acetic acid. The other half was coated with equal quantity one per cent glacial acetic acid. The whole samples were packed under vacuum in PA-PE pouches. Half of the packets from each treatments were irradiated at 2.5 kGy employing Gamma Chamber 5000. Sufficient numbers of packets from each treatment were stored under room temperature (25-30°C) and in chiller (1-4°C). Samples were analysed for proximate composition on the day of preparation and for TBARS, TV, microbiological and organoleptic qualities on day 0, 5, 10, 15, 20, 30, 40, 50, 60 and 70 of chiller storage, while those at room temperature on day 0, 5, 10 and 15 or until spoilage, whichever was earlier. Shelf life of chicken fry was assessed based on the physical signs of spoilage. The spoiled samples were not subjected to any further analysis. The non-irradiated control samples had a shelf life of 5.33±0.23 days at room temperature and 28.16±0.33 days in chiller. The shelf life was extended to 7.33, 8 and 10 days for CH-NIR, IR and CH-IR samples respectively at room temperature. In chiller storage, the samples were consumable up to 67 days (IR) and 73 days (CH-IR). The proximate composition of the product analysed on the day of preparation was not significantly affected due to irradiation or chitosan coating. The TV showed a decreasing trend due to irradiation whereas the TBARS values were increased and it was controlled by chitosan coating. Storage had a significant effect in increasing both these physicochemical qualities. Aerobic plate count, psychrotrophic plate count and yeast and mould count were significantly reduced due to irradiation, chitosan coating and their combination. Whereas the extend of reduction due to chitosan coating alone was not up to the combined effect of chitosan coating and irradiation. As storage period enhanced the counts increased. The increase was rapid in room temperature stored samples and it was slow and steady in chiller samples. As the storage period enhanced, in the chiller stored products, the survived bacteria might have multiplied and count has gone up beyond the initial count as evidenced by the higher count in terminal end of the storage period. The organoleptic qualities were assessed with help of nine point Hedonic scale. The colour, juiciness, tenderness and overall acceptability of the product were improved by irradiation, chitosan coating and their combination. But flavour showed a decrease in score. A gradual decrease in organoleptic qualities was observed due to storage. Even after 60 and 70 days of chiller storage, the samples had an overall acceptability score of above 7 indicating the samples are preferred by the consumers. The cost of chicken fry was Rs. 109.83 per kg and addition of chitosan at a level of 0.5 per cent increased the cost of the same by Rs. 4.38 per kilogram. The irradiation preservation of ready-to-eat chicken fry was beneficial for enhancing the keeping quality of the product under chiller conditions without affecting the qualities. Some of the bad effects of irradiation like increase in fat rancidity can be controlled by the beneficial coating with natural antioxidants like chitosan. Microbial count like aerobic plate count, psychrotrophic count, yeast and mould count were significantly (P<0.05) reduced due to irradiation at 2.5 kGy, the lowest limit prescribed by PFA. The hurdle technology combined with irradiation and chitosan coating has significantly increased the keeping quality of the product. Considering the extended shelf life, wholesomeness of the product, reduced microbial load and energy saving aspects, chitosan coating followed by irradiation can be advocated as a suitable method for preservation of ready-to-eat value added meat products.