Mangrove Oysters: Mortality and Microbiota Population Dynamics during Processing and Ambient Storage

The molluscan bivalve shellfish Mangrove Oyster (Crassostrea gasar) is a typical inhabitant of the mangrove / estuarine ecosystem of Nigeria’s Niger Delta. The dynamics of mortality and microbiota population of fresh, processed and stored mangrove oysters were investigated at ambient temperature. During purification in tap water (TW) and brackish water (BW) microenvironments, the mortality rates of raw oysters were calculated for 14 days. In the environment, mortality was observed on the 5th, 11th and subsequent days , respectively. The shelf-life of oysters was greatly improved in BW microcosms. It thus shows the beneficial effect of mangrove oyster depuration in BW as opposed to TW microcosms. Using standard microbiological methods, the microbial counts of raw (shucked), processed and oyster meat samples during ambient storage were determined. The aerobic plate counts (APCs) for raw (shucked) and processed oyster meat samples on day 0 were 1.36 ⁇ 105 and 3.00×103 CFU / g, respectively, but After storage, it increased from 0-0.8 to 102 CFU / g. In numbers and variety, bacteria were more prevalent than fungi. Bacillus, Pseudomonas, Vibrio, Proteus and Staphylococcus were the most commonly isolated microbes from raw (shucked), processed and preserved oyster meat samples, while others were Aspergillus, Penicillium and Fusarium. Bacillus (20,8 percent) and Pseudomonas (16,7 percent); Aspergillus (52,3 percent) and Penicillium (45,4 percent) were the most dominant genera during storage. Non-detectability of Escherichia coli and Acinetobacter species as well as bioburden reduction, however, underlines the criticality and necessity of sufficient pre-consumption heat treatment for oysters, as some of these organisms are not only potentially pathogenic, but also of public health significance. This study highlights the marketability of depurated mangrove oysters to boost health risks and severe post-harvest economic losses on or before 5 days and 24h for processed samples.

Author (s) Details

Lawrence O. Amadi
Department of Microbiology, Faculty of Science, Rivers State University, P.M.B. 5080, Nkpolu-Oroworukwo, Port Harcourt, Nigeria and Department of Microbiology, School of Applied Science, Ken Saro-Wiwa Polytechnic, P.M.B. 20, Bori, Rivers State, Nigeria.

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