Changes in Quality Characteristics of Crassostrea gigas Oysters during Hypothermic Storage

Now oysters are one of the most common representatives of aquaculture grown worldwide. Finding reliable ways to assess the quality of oysters is an important task for breeding professionals and users of these products. The Food and Agriculture Organization considers microbiological testing and organoleptic parameters as mandatory tests for evaluation of the mollusks’ safety. We believe these parameters in oysters are insufficient for unbiased evaluation of the condition of mollusks. In this research, we attempted to determine the most sensitive indices of oysters’ viability during hypothermic storage under anoxia conditions. We investigated the oysters during 6 days of their storage in a household refrigerator at a temperature of 5°C. According to microbiological studies, during the experiment, we expected a rise in the total number of microorganisms. However, there was a paradoxical situation when at the end of the observations the total number of microorganisms decreased significantly, which contradicted the negative assessment of the state of oysters by organoleptic parameters. Flow cytometry studies also showed no correlation between the percentages of necrotized and apoptotic cells to organoleptic parameters. Studies have shown that on day 3 of storage, the oysters demonstrated a partial deterioration in organoleptic characteristics, which is clearly reflected in the content of volatile basic nitrogen in the tissues of mollusks, which characterizes the protein breakdown and accumulation of toxic nitrogen compounds. Thus, the content of volatile basic nitrogen in the tissues of oysters is the most sensitive and significant parameter in terms of biosafety of mollusks. Keywords: hypothermic storage, oysters, microbial flora, food quality, nitroge