Effect of lactic acid bacteria or yeast as co-inoculants with Aspergillus oryzae in koji making on the flavor properties of walnut meal-based soy sauce

elevated total acids by 33% and ketones to 54.7% relative content. Triple co-inoculation fermentation achieved the highest umami (7.8 point) and soy sauce-like flavor (8.2 point) with minimal bitterness. Metabolic pathway analysis revealed that key flavor compounds were associated with glycolysis, organic acid, and amino acid metabolism. These findings provide new insights into optimizing the flavor and quality of WSS through mixed-culture fermentation.