Publisher: Bachudo Science Co. Ltd

Bacterial Inhibitory Effects of Potassium Sorbate and Retardation of Spoilage of Oysters (CRASSOSTREA GASAR) At Two Storage Temperatures

B. J. O. Efiuvwevwere, G. Izakpa
KEYWORDS: Oysters, microqial inhibition, sorbate, temperature


Shucked oysters (Crassostrea gasar) treated with 0.1 % or 0.2% w/v potassium sorbate (KS) or untreated (controls) were stored at 5°C or 29°C to evaluate microbial changes and shelf-life. Appreciable variations were observed in the microbial composition, with a Gram-positive to Gram-negative flora ratio of 51 :46 occurring in freshly shucked samples. But contrasting ratios of 22:78 and 80:20 occurred in 0.2% KS1 treated samples stored at 5°C and 29°C respectively. Pseudomonas spp. {65%) were most prominent in samples stored at 5°C while Gram positive flora (Bacillus spp, 40% and Micrococcus spp. 25%) dominated samples held at 29°C. Of the fungi, Saccharomyces cerevisiae was most prevalent. in the samples regardless of KS treatment and storage temperature. Total_ plate counts {TPCs) were reduced by approximately 100-fold in 0.2% KS-treated samples stored at 5°C but KS treatment was less effective in samples held at 29°C. The quality indicators (TPCs, coliform bacteria and Vibrio spp, population) increased substantially with storage at 29°C. Correlations between total and faecal coliforms or between the latter and Vibrio spp. were dependent on KS treatment and storage temperature. pH decreased in all samples especially in cor1trols. Samples stored at 29°C were rejected within 36h of storage but combination of 0.2% KS treatment with storage at 5°C extended the shelf-life by approximately 4 days. The preponderance of Bacillus spp., ,Staphylococcus spp. and Vibrio spp. with the concomitant high TPCs in samples stored at 29°C have demonstrated the public health risks associated with shucked oysters subjected to inadequate-KS treatment and storage temperature.

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