Impact of gamma radiation on the microbiological quality of smoke dry shrimp (Penaeus notialis) from three different water sources in Ghana

Abstract

Shrimps are one of the most important commodities of the global fishery trade, are consumed by humans and also used in formulation of feed for animals to enhance nutrition. Enumeration and identification of fungi and bacteria present on shrimp was checked. Gamma radiation doses of 0, 4, 8 and 10 kGy at a dose rate of 1.7 kGy/h from a Cobalt-60 source (SLL-515, Hungary) was evaluated. Mycological analysis was done by direct plating method on Oxytetracycline Glucose Yeast Extract and Dichloran Rose Bengal Chloramphenicol (DRBC) media. Bacteriological analysis was done by decimal reduction method on Plate Count Agar. Some toxigenic species of the genus Aspergillus (A. alutaceus, A. flavus, A. candidus and A. fumigatus), Fusarium (F. verticillioides) and Penicillium (P. expansum, P. citrinum and P. cyclopium) were isolated from the shrimp. Comparatively higher initial fungal and bacterial counts of 5.0–5.4 log 10 CFU/g and 4.3–4.7 log 10 CFU/g, respectively, were recorded for non-pretreated while lower counts of 1.7–2 and 1.6–2.1 log 10 CFU/g were recorded for pretreated smoked dry shrimp. Gamma radiation significantly (P < 0.05) reduced initial total fungal and bacterial populations by an average of 3 and 2.5 log cycles, respectively.