The optimization of quality in soybean paste: A study based on combining lactic acid bacteria isolation and purification technology with multi-sensor technology

Abstract

As a traditional fermented food, soybean paste is influenced by various factors in terms of its quality characteristics, among which microorganisms serve as the core driving force during the fermentation process, playing a crucial role. However, most commercial fermentation agents for soybean paste currently focus primarily on fungi, with relatively limited research on lactic acid bacteria. Therefore, this study integrated lactic acid bacteria isolation and purification technology with multi-sensor technology to thoroughly investigate the role of lactic acid bacteria in the fermentation process of soybean paste and successfully screened a high-quality auxiliary starter culture for soybean paste-Lactiplantibacillus plantarum DJ-2-4. This strain exhibits remarkable salt tolerance, being capable of growing well at a salt concentration of 8 %–12 %. Its high acid-producing ability enables the pH of the fermentation broth to drop to the range of 3.5–4.0 within 14 h, and it also possesses strong proteolytic activity. When co-cultured with Aspergillus oryzae, it shows a good growth status. In addition, employing Lactiplantibacillus plantarum DJ-2-4 as an auxiliary starter can significantly enhance the quality, safety, and flavor of soybean paste. Specifically, it can reduce the levels of aflatoxin B1, nitrite, and biogenic amines in soybean paste to safe thresholds, elevate the amino nitrogen content during the early stage of fermentation, increase the content of flavor compounds such as 3-methylbutyric acid and ethyl 3-methylbutyrate, and improve the texture of soybean paste. Moreover, it was also found that 1-octen-3-ol, 2-methylbutanoic acid, 3-methylbutanoic acid, and butanoic acid play a key role in the flavor profile of soybean paste. These research findings offer crucial theoretical foundations and technical supports for optimizing the production process of soybean paste and enhancing its product quality.