Effects of different lactic acid bacteria on the quality of fermented grass carp (Ctenopharyngodon idella)

There is large catch of fishery in China, due to the rich nutrients, high moisture content, and protease activity in fish meat, fresh fish meat is more inclined to spoilage and deterioration after death than other meats, which reduces its utilization rate. Therefore, it is necessary to take effective preservation measures. Fermentation, as a traditional food processing and preservation skill, can be used to improve the taste and flavor of food, increase its nutritional value and edible safety quality. Fermentation uses microorganisms to convert carbohydrates into lactic acid. The accumulation of organic acids causes pH value to drop and inhibits the growth of spoilage bacteria. The enzymatic hydrolysis of microorganisms promotes protein denaturation and degradation, fat degradation and oxidation in fish meat, promotes texture improvement, nutritional value enhancement, and unique flavor generation of freshwater fish products, thereby realizing the value-added utilization of freshwater fish products. Fermented fish is a fish product that uses various enzymes in the fish and environmental microorganisms to form inhibitory metabolites through microorganisms based on pickling, reducing water activity, and preventing spoilage. Fermented food has a long history in China. Traditional fermented fish products have a simple production process and can be completed under ordinary household conditions. The process is mostly natural fermentation and manual operation, so there are more family-style workshops. The fish meat is inoculated and fermented with a good starter to prolong the storage time at room temperature and produce a good flavor. As one of the most common starters, lactic acid bacteria play an important role in the fermentation of various fish products. At present, there are many studies on the application of lactic acid bacteria in the fermentation of fish products, but there are few reports on the application of Lactobacillus plantarum, Pediococcus pentosus and L. paracasei in the fermentation of grass carp (Ctenopharyngodon idella), respectively. In this study, the number of microorganisms and physicochemical properties of fermented C. idella were determined in order to investigate the effects of different lactic acid bacteria during fermentation of C. idella and to further improve the quality of fermented fish products. In order to investigate the effect of different lactic acid bacteria on the quality of C. idella during fermentation, the microorganism, pH value, total acid, moisture content, whiteness, amino acid nitrogen, thiobarbituric acid, and volatile base nitrogen of C. idella dorsal meat were analyzed with different fermentation time (0-15 d). The results showed that compared with the natural fermentation, lactic acid bacteria grew rapidly in C. idella meat after inoculation, so the pH value decreased to 4.03±0.02 and the total acid content increased to (23.70±1.06) g/kg, which could effectively inhibit the reproduction of spoilage bacteria. At the same time, the whiteness of C. idella meat was improved. The content of amino acid nitrogen in C. idella meat was increased. The moisture content and the production of volatile basic nitrogen were reduced. Among them, at the end of fermentation, P. pentosaceus had the greatest impact on the decline of moisture content. Compared with the other two groups, LP group had higher whiteness and lower TVB-N value, but its ANN content was significantly lower than the other two groups, and L. plantarum had poor ability to degrade protein. In conclusion, inoculating lactic acid bacteria fermentation can reduce the lag time of fermentation start, delay the deterioration of C. idella meat, improve the nutritional value and color, and improve the quality of fermented C. idella.