Synergistic effect of gamma irradiation and proper packaging for the control of insects in smoked shrimps (Penaeus notialis) from three different water bodies in Ghana

Abstract

Damage caused to stored dried shrimps by insect pests is problematic and are often underestimated. The incubation, identification, and control of these insect pests which infest shrimps from three water sources; sea, lagoon, and river were evaluated according to standard procedures of the Entomological Society of Canada. Exposure to gamma ionizing radiation was undertaken from a Cobalt 60 source (SL 515, Hungary) and radiation doses of 0, 4, 8, and 10 kGy at a rate of 1.7 kGy/hr were used. The hidden insects identified were Necrobia rufipes (Copra beetle), Dermestes maculatus De Geer (Hide beetle), and a mite Lardoglyphus sp. belonging to the family Acaridae in the mite group Astigmata. An after-feeding test on shrimps by insects revealed a weight reduction by 17%, 14%, and 26% for sea, lagoon, and riverine shrimps respectively. These observations were statistically significant at p ≤ 0.05 level. After 2 months of storage there was generally a 43.0 % reduction in weight which was significantly different (p ≤ 0.05) from the initial weight. Moisture sorption isotherms of dehydrated shrimps were also checked at 20, 55, 65, 75, 85, and 95% of Effective Relative Humidity (EHR) and revealed a general trend of sigmoid shape. The prescribed dose of 8–10 kGy was able to kill all insects and rendered the product insect-free in airtight dense polypropylene containers used in these investigations.

Keywords

• insects
• dried shrimps
• penaeus notialis
• gamma irradiation
• moisture isotherms
• ghana