Shelf-life extension of dried shrimps by irradiation and packaging techniques

摘要

Dried shrimps were air-packaged or N_2-packaged in the flexible pouch of oriented polypropylene (OPP), polyvinylidene chloride coated polypropylene (KOP) and ethylene vinyl alcohol copolymer (EVOH). The packages were irradiated with gamma ray from cobalt 60 at 3 and 8 kGy. Non-irradiated dried shrimps were used as a control. The samples were stored at 30 deg C and 70 +- 5 percent RH for 4 months. Non-enzymatic browning induced the discoloration of dried shrimps, and oxidation of astaxanthin proceeded after irradiation and during storage. The hunter color difference, #DELTA#E, of all the samples was increased, especially in the non-irradiated air-packages samples. The decrease in astaxanthin content was found in both air - and N_2-packaged samplesduring storage. The number of microorganisms was reduced by irradiation dose of 3 and 8 kGy from 6.5 to 4.2 and 2.7 log CFU/g, respectively. The decreased concentration of O_2 in the package also reduced the number of microorganisms. The air-packaged dried shrimps in the OPP pouch deteriorated during storage. Shrinkage of the pouches and growth of halophilic bacteria on the surface of dried shrimps were found at a_w of 0.75. The discoloration of dried shrimps in the OPP pouch was more significant than that in other pouches. Irradiation at 3 and 8 kGy in combination with packaging in KOP and EVOH pouches containing N_2 atmosphere was one of the promising methods for prolonging shelf-life of dried shrimps at room temperature.