Shelf life of irradiated rabbit meat underaerobic and vacuum packaging

Abstract

Prevention of Food Adulteration Act (1954) as amended in 1998 has permitted irradiation at a dose rate of 2.5 to 4.5 kGy to control pathogenic microorganisms and to extend the shelf life of meat and meat products including poultry products. A study was conducted to evaluate the shelf life of irradiated rabbit meat under aerobic and vacuum packaging. The rabbit meat was prepared by slaughtering locally purchased rabbits under hygienic conditions and was packed in HDPE and PAPE packages at a rate of 120 g each. Half of the packets of aerobic and vacuum packaged samples were subjected to gamma radiation at 2.5 kGy at melting ice temperature and kept immediately at chiller temperature (1 to 4oC) and domestic refrigerator freezer (-6 to -8oC). Samples were analyzed for physical, physicochemical, microbiological, and organoleptic qualities on the day of preparation and on days 3, 5, 10, 15, 20, 25, 30, 40, 45, 50, 60, and 70 of storage or until spoilage, whichever was earlier. The samples were also analyzed for proximate composition on the day of preparation. The dressing percentage of the rabbits subjected to the study was 49.35 per cent. The keeping quality of the rabbit meat was 15 to 18, 17 to 19, 5 to 7 and 7 to 9 days in HDPE IR, PAPE IR, HDPE NR and PAPE NR respectively at chiller temperature. In freezer temperature it was significantly (P < 0.05) increased to 45 to 47, 47 to 49, 25 to 27 and 27 to 29 days in HDPE IR, PAPE IR, HDPE NR and PAPE NR respectively. Irradiation or packaging did not significantly (P < 0.05) affect fat, protein and ash composition but higher moisture percentage was observed in irradiated samples. Swelling of the collagen fibres was noticed in irradiated samples on histological examination. The physicochemical parameter, pH of irradiated and non-irradiated samples varied significantly (P < 0.05) on the day of preparation. On storage the pH values decreased uniformly. The WHC was significantly (P < 0.05) reduced in irradiated samples. The ability of the rabbit meat to retain its water decreased gradually on storage and a reduction of about 40 per cent could be noticed from the initial level. Drip loss was not significantly (P < 0.05) different on the day of preparation. Irradiation had a significant (P < 0.05) effect in enhancing the cooking loss whereas packaging had little effect. Both drip loss and cooking loss was increased significantly (P < 0.05) due to storage under chiller and freezer temperature. Irradiation had a significant (P < 0.05) role in increasing the TBARS value of rabbit meat. As the days of storage enhanced, the TBARS values were increased. Irradiation had a significant (P < 0.05) effect in reducing the TV in both type of packaging. As storage period enhanced, TV increased with significant (P < 0.05) changes among treatments. Irradiation had a beneficial effect on microbiological qualities of rabbit meat. There was a significant (P < 0.05) reduction of nearly three log in APC of irradiated meat from that of control. The irradiation of the samples both in HDPE and PAPE packaging significantly (P < 0.05) reduced the PC of meat on the day of preparation where as storage had significant (P < 0.05) effect in enhancing the microbial load of meat. The colour score was non-significantly (P < 0.05) higher in irradiated samples. The juiciness, tenderness and overall acceptability scores were improved significantly (P < 0.05) due to irradiation, where as flavour score was reduced. The sensory attributes were significantly (P < 0.05) reduced due to storage in all the treatment groups. The keeping quality of rabbit meat was significantly (P < 0.05) increased by irradiation both in chiller and freezer under different packaging. In addition irradiation could effectively control food borne illness by destroying the major pathogenic organism without affecting the sensory and nutritional quality of the product. Considering these advantages it can be recommended that packaging the meat in PAPE packages followed by low dose gamma irradiation and maintaining the cold-chain contribute to extended storage life of rabbit meat.