Optimization of rapid fermentation processing of paste produced with shrimp head by adding mixed strains

Abstract: Shrimp paste is a kind of traditional fermented aquatic product seasoning with delicious taste, and it contains various nutrients and is popular in coastal areas and Southeast Asian countries, and it is one of the commonly used seasonings. Shrimp paste is rich in protein, calcium, carotenoids and chitin. It has antioxidant activity, cholesterol lowering, blood pressure lowering and organism immunity enhancement, and it has a wide application space in the functional food field. However, the shrimp paste industry in China has the problems of long fermentation cycle and high salinity, which restricts the development of its industrialization. In this paper, shrimp head paste was prepared by inoculation with mixed strains, and the parameters of rapid fermentation process were optimized by response surface method (RSM), so as to achieve the goal of increasing the production rate and stable production. Microorganisms isolated from the traditional shrimp paste, such as saccharomycetes Pichia gilliermondii and mold fungus Aspergillus niger and the standard microorganisms Lactobacillus planticola purchased, were added as mixed strain to improve the flavor of shrimp head paste. Based on the sensory evaluation value and amino nitrogen content, the effect of different sterilization processes on shrimp head paste was compared, and the result showed the highest content of amino nitrogen and sensory evaluation value in shrimp head paste fermented after pasteurization. It shows that the fermentation degree is higher; based on the amino nitrogen content, the mixing ratios of the 3 kinds of microorganisms were investigated, and the results showed that the optimal mixing ratio of yeast, mold and lactic acid bacteria was 1∶5∶3. The conditions of shrimp head pasta fermented by mixed strains were optimized through the single factor experiment, and factors included fermentation temperature, fermentation time, and mixed strains inoculation. The result showed that fermentation temperature, fermentation time, and mixed strains inoculation had significant influence on the fermentation of shrimp head paste by mixed strains. And the suitable conditions in the fermentation of shrimp head paste were fermentation temperature of 50 ℃, fermentation time of 12 d, and mixed strains inoculation of 3 mL/100g. The conditions of shrimp head paste fermented by mixed strains were optimized through Box-Benhnken central composite experimental design based on the indicators of the sensory evaluation, and the optimized technological conditions were: fermentation temperature of 53.6 ℃, fermentation time of 13.46 d, and mixed strains inoculation of 2.69 mL/100g. These 3 factors affecting the sensory evaluation value in descending order were fermentation time, fermentation temperature, and mixed strains inoculation. The sensory evaluation value of shrimp head paste prepared under the optimum conditions was 7.64, and the relative error was 0.521% between predictive sensory evaluation value (7.68) and true sensory evaluation value. By comparing the changes in the flavor and amino nitrogen content between fast fermented shrimp head paste and traditional fermented shrimp paste, it can be found that the rapid fermentation process can make the product mature in a relatively short period of time to form a better flavor of shrimp head paste. This study provides an industrial basis for the rapid fermentation of shrimp head paste and effectively improves the high-value utilization of shrimp by-products.