LC-MS/MS-based metabolomics and multivariate statistical analysis reveal the mechanism of yeast extracellular proteases on myofibrillar protein degradation, metabolite development and sensory characteristics improvement

Yeast extracellular proteases play a key role in developing the taste of dry-cured ham, whereas the mechanism of yeast proteases on taste formation of dry-cured ham is not fully studied. The proteases characteristics of yeast isolated form Jinhua ham, hydrolysis capacities for myofibrillar proteins (MP), free amino acid contents, metabolite compositions, taste parameters and the relationship between metabolites and taste parameters were investigated to reveal the mechanism of Rhodotorula mucilaginosa AUMC 9298 (RM) and Candida parapsilosis d70a (CP) proteases on MP hydrolysis and taste development of dry-cured ham. The proteases of RM and CP showed high hydrolysis activities at the conditions of pH 5.0-8.0 and 30-50 °C. The proteases of RM showed higher capability to degrade myosin compared with CP proteases and Pichia kudriavzevii XS-5 (PK) proteases. The total free amino acid contents increased from 18.44 mg/100 mL in PK to 33.91 mg/100 mL in RM and 25.28 mg/100 mL in CP after 4 h hydrolysis of MP. Thirty-two metabolites were identified by LC-MS/MS, and peptides and amino acid derivatives were the key components of MP hydrolysates. The scores of umami, richness and aftertaste showed the largest values in RM among these groups. PLS-DA and correlation demonstrated that aspartic acid, N-Methyl-aspartic acid, Glu-Glu, γ-Glu-Cys, glutamic acid, γ-Glu-Glu and γ-Glu-Gln were positive correlation with the improvement of umami, richness and aftertaste.