High temperature steaming pretreatment improves quality and flavor of the walnut meal soy sauce

Heat pretreatment can enhance the physicochemical, structural, and functional characteristics of walnut meal (WM). In this study, the fermentation properties of high temperature steam pretreated (HTSP) WM were investigated. After HTSP, the protease and glycolytic activities in the walnut meal soy sauce (WMSS) during the koji fermentation were improved compared to the control. Additionally, the contents of amino acid nitrogen and total nitrogen of S115 were increased by 24.56% and 15.00% during moromi fermentation. Combining the results of E-nose, E-tongue and sensory evaluation, the umami tasty and soy sauce aroma of WMSS had improved after HTSP. Further, a total of 173 metabolites were identified by GC-MS in WMSS, compared to the control, the content of amino acid improved after HTSP, and the content of umami amino acids in S115 was improved by 71.91%. Consequently, this study provides theoretical guidance for the application of HTSP in soy sauce. • High-temperature steam pretreatment (HTSP) improves the soluble protein of walnut meal. • The content of amino acid nitrogen of walnut meal soy sauce (WMSS) was increased by 24.56 % at 115 °C. • HTSP improved the umami and soy sauce aroma of WMSS. • The content of umami amino acid was increased by 71.91%.