Mixed Microbial Fermentation-Induced Quality Upgrade of Rapeseed Meal: Volatile Metabolite and Differential Protein Analysis via Multi-Omics Methods

Rapeseed meal (RSM), a major agricultural byproduct, is limited in application due to high anti-nutritional factors like glucosinolates, while microbial fermentation can improve its nutritional and flavor profiles. This study combined physicochemical analyses, volatile metabolomics, and quantitative proteomics to investigate flavor evolution and protein dynamics during RSM fermentation. Results showed RSM reached optimal quality at 40 h fermentation, with increased soluble protein and peptides, decreased glucosinolates, and HS-SPME-GC-MS and electronic nose analysis identified that esters, terpenoids, ketones as dominant volatile compounds, 3(2H)-furanone, dihydro-2-methyl-, Benzenemethanethiol is a key volatile differential metabolite. Proteomics analyzed a total of 51 differentially expressed proteins (DEPs), which are mainly involved in organonitrogen compound, peptide and protein metabolic. Additionally, these DEPs were identified to have significant correlations with 13 differentially accumulated volatile metabolites. These findings provide a theoretical basis for the high-value valorization of rapeseed meal, proposing feasible pathways for its use as a condiment base or a functional ingredient in bakery products.