Changes In The Microflora And Quality Of Pacific Oysters During Ice And Frozen Storage

The changes of microflora and quality of Pacific oysters were studied in this paper. A system based on organoleptic, chemical, and microbiological analysis for oyster quality evaluation was established. The effect of Ozonated water, BFX, Biopreservatives and Modified Atmosphere Package (MAP) on the shelf life and microflora were studied. A model for predicting shelf life of oysters was also established. The results showed that the shelf life of oysters at 0℃,5℃and 10℃are 17 days, 10days, 7 days, respectively. At the point of sensory rejection, the dominant organisms were found to be Pseudomonas regardless of the storage temperatures. The treatment of Ozonated water extended the shelf life of oysters by 2 days. Ozonated water did not alter the dominant organisms in the process of spoilage and the spoilage organism was found to be Pseudomonas. BFX extended the shelf life of oysters by 4 days, and altered the dominant organisms in the spoilage process. At the point of sensory rejection, the dominant organism was Moraxella. The preservatives extended the shelf life of oysters by 9 days. At the end of shelf life, the dominant organism was Lactococcus. MAP can extend the shelf life of oyster, and the storage temperature was important. The dominant organisms in samples packaged with CO2/N2/O2 were Corynebacterium (stored at 5℃) and Micrococcus (stored at 0℃). The total counts of oysters decreased at first, then increased during -3℃storage.The proposition of Pseudomonas increased all the time during storage, and become the predominant germ. The total counts of oysters decreased when stored at -20℃. Because of the relative high resistance against freezing, the proportions of Flavobacterium,Staphylococcus,Micrococcus,Lactococcus and Lactobacillus attained 28%,16%,22%,12% and 16% respectively after 90 days and became the predominant germs of oysters during -20℃storage.