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 3.00x103 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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