Gamma Radiation Processing of Clam (Galatea Paradoxa Born 1778) from the Volta River Estuary for Microbiological Decontamination

Abstract

The Clam (Galatea paradoxa Born 1778) is a dermesal dweller of riverine water and filter feed by passing water through gut concentrating particulate matter including bacteria in the gut and mantle. Microbial profile of contaminating bacteria and their sensitivity to gamma irradiation (0 – 20 kGy) were ascertained in vivo and in vitro under laboratory conditions. Conventional cul-tural and morphological characteristics were used to detect the resident Total Aerobic Bacteria (TAB), Total Heterotrophic and Total Coliform bacteria (TC) populations in the clam and the species encountered were confirmed using biochemical methods and the API 20E identification kit. Twenty (20) bacteria species in the samples belonged to 18 genera (Acinetobacter, Aeromo-nas, Chromobacterium, Citrobacter, Enterobacter, Escherichia, Flavobacterium, Klebsiella, Mi-crococcus, Morganella, Proteus, Pseudomonas, Salmonella, Serratia, Staphylococcus, Strepto-coccus, Vibrio and Yersinia) predominated by Acinetobacter (22%), Staphylococcus aureus (12%) and Klebsiella ornitholytica (11%) in the clam mantle and Pseudomonas aeruginosa (32%), Klebsiella ornitholytica (24%) and Flavobacterium meningosepticum (12%) in the water. A dose of 20 kGy eliminated all microorganisms in the “in vitro” studies; at 15 kGy only two bacteria species Micrococcus radiodurans and Vibrio cholera survived. The most radio resistant species was M. radiodurans (D10=6.19 kGy), followed by Vibrio cholera (D10=5.2 kGy). A dose of 10 kGy eliminated Staphylococcus aureus (D10=1.7 kGy). Practical implications from these find-ings are discussed in the light of food safety of preserved clams.