This study explored the effect of electrical stimulation (ES) and Pediococcus pentosaceus LL-07 ( P. pentosaceus LL-07) and Staphylococcus simulans QB7 ( S. simulans QB7) on the quality and microbial community of loin ham during the ripening. After the ES and starter culture treatments, the Aw and pH were decreased. Surface hydrophobicity, myogenic fiber fragmentation index (MFI), TCA-soluble peptide, amino nitrogen and free amino acids (FAAs) were also significantly higher than the control group (CK) ( P < 0.05). This increase was more significant in the E-S group (electrical stimulation followed by inoculation with P. pentosaceus LL-07 and S. simulans QB7) than the rest of the experimental group (E、S、S-E group). Furthermore, the CK and E-S groups were subjected to a bacterial community comparison experiment. The microbial diversity of these two groups was increased. Pediococcus spp. and Staphylococcus spp. became the dominant bacteria in E-S groups during the ripening. Correlation analyses show a strong correlation between protein hydrolysis, microorganisms and FAAs. In conclusion, the combination of ES and starter culture could promote protein hydrolysis, the accumulation of FAAS, and improves the bacterial community of loin ham.
Protein degradation occurs during the fermenting of traditional mutton sausages, which influences on the flavor and quality of products. In this study, HS-SPME-GC-MS and Sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to study the degradation kinetics of myofibrillar protein (MP) and sarcoplasmic protein (SP) during fermentation and ripening of fermented sausages by single and mixed starters ( Pediococcus acidilactici CICC 10344 and Rhizopus Oryzae ATCC 96382). It was shown that flavor formation and protein degradation are related. Adding mixed starters effectively reduced the loss of sulfhydryl content compared to single starter. Moreover, cathepsin B and cathepsin L activities were continuously enhanced during sausage fermentation. Analysis of SDS-PAGE showed processing affected protein degradation, and the degree of degradation was increased with increasing fermentation time. Meanwhile, the inoculation of mature sausage samples with mixed starters accelerated the production of water-soluble flavor compounds (e.g., free amino acids and TCA-soluble peptides). The mixed starters group had more amino acids presenting the umami-free amino acids. Based on the ROAV values for odor thresholds, we identified 12 key volatile flavor compounds. The correlation heat map showed higher concentrations of key volatile flavor compounds in the mixed starters. Overall, Pediococcus acidilactici and Rhizopus Oryzae addition may effectively improve the flavor quality of fermented sausage products during fermentation.
危险品化学品经营许可证（带存储）