Effect of Lactiplantibacillus plantarum and Saccharomyces cerevisiae Inoculation on Quality of Suanyu: Focusing on the Protein Degradation and Flavor Profiles Analysis

To investigate the effects of Lactiplantibacillus plantarum (LP) and Saccharomyces cerevisiae (SC) inoculation on quality of Suanyu, the related chemical parameters such as moisture content, protein degradation index, tricarboxylic acid (TCA) cycle soluble peptides, SDS-PAGE, free amino acids, volatile flavor compounds, and sensory characteristics were analyzed. Natural fermentation (NF), LP fermentation, and SC fermentation were used as control groups. The results indicated that Suanyu samples inoculated with LP and SC (MF) exhibited a significant reduction in moisture content, while simultaneously accelerating the degradation of myofibrils and myosin. This was confirmed by the fading or disappearance of corresponding bands in SDS-PAGE, as well as the appearance of high-molecular-weight protein aggregates. Furthermore, the content of TCA-soluble peptides and free amino acids in the MF group also increased significantly after fermentation, particularly umami amino acids (20.56%) and sweet amino acids (34.14%). With regard to volatile compounds, the addition of SC made a significant contribution to the formation of alcohols and esters. Sensory evaluation confirmed that the MF group exhibited superior performance in terms of flavor, aroma, and overall sensory characteristics. Overall, the combination of LP and SC better promotes protein hydrolysis and the formation of flavor compounds in Suanyu. This study provides a theoretical basis for optimizing starter cultures and promoting the industrial production of high-quality fermented fish products.