Xuefei Shao,Baocai Xu,Hui Zhou,Conggui Chen,Peijun Li
The mechanism of decreasing N- nitrosodimethylamine (NDMA) by Lactobacillus pentosus R3 isolated from Chinese dry sausage was assessed in a model system. The model system was devised using a DeMan-Rogosa and Sharp-ferrous sulfate broth supplement with NDMA or its precursors. The results showed that inoculating L. pentosus R3 could significantly decrease the content of NDMA ( P < 0.05). The NDMA precursors (dimethylamine and putrescine) were found to be decreased by L. pentosus R3 ( P < 0.05). Nitrite was degraded to nitrosonium cation by acidolysis, which may promote the formation of NDMA. Direct degradation of NDMA by L. pentosus R3 was also observed. The strain exhibited antioxidant activities , including Fe 2+ chelating activity, which may be responsible for inhibiting the formation reaction and decreasing the precursors of NDMA. Thus, L. pentosus R3 decreased the content of NDMA possibly by three ways: inhibition of the formation reaction, decrease in precursors (DMA and putrescine) and direct degradation. It is interesting to understand the mechanism of decreasing NDMA by L. pentosus R3 to improve the safety of fermented meat products .
Jiasheng Lu,Yumeng Sui,Xin Liu,Jiawang Wang,Jiatong Li,Baohua Kong,Qian Chen,Weiwei Yang
The present study aimed to investigate the impact of 4,5-dihydroxy-2,3-pentanedione (DPD; 0, 300, 600, and 900 nmol/L), a crucial precursor in the LuxS/ AI-2 quorum sensing system, on flavour formation by Lactiplantibacillus plantarum HRB1 both in vitro and dry-sausage model. Firstly, L. plantarum HRB1 was selected from 18 strains of lactic acid bacteria due to its superior AI-2 and protease activity. In vitro , DPD significantly increased the activity of the AI-2 and the protease activity of L. plantarum HRB1. In the fermented dry-sausage, free amino acid content was significantly higher in the treatment with 600 nmol/L DPD compared to the other treatments. Notably, the dry sausage treated with 600 nmol/L DPD exhibited the highest concentrations of aldehydes (558.50 μg/kg), ketones (192.41 μg/kg), alcohols (1175.56 μg/kg), acids (202.27 μg/kg), esters (1504.48 μg/kg), and terpenes (1319.82 μg/kg). Sensory analysis revealed that the dry sausage treated with 600 nmol/L DPD had the most pronounced fermented and fatty odour. These results suggest that 600 nmol/L DPD enhances the flavour formation of L. plantarum HRB1. This research provides a theoretical foundation for utilizing the LuxS /AI-2 QS to optimize microbial fermentation processes and improve fermented food quality, especially flavour.
Yeast strains are promising starters to compensate for the flavor deficiencies of reduced-salt dry sausages, but their influence on the bacterial community’s structure has not yet been clarified. In this study, the effect of separately inoculatingPichia kudriavzeviiMDJ1 (Pk) andDebaryomyces hanseniiHRB3 (Dh) on the bacterial community structure in reduced-salt dry sausage was investigated. The results demonstrated that the inoculation of two yeast strains significantly reduced the pH, and enhanced the total acid content, lactic acid bacteria (LAB) counts, and total bacterial counts of reduced-salt sausages after a 12-day fermentation (p< 0.05). Furthermore, high-throughput sequencing results elucidated that the inoculation of yeast strains significantly affected the bacterial composition of the dry sausages. Especially, the relative abundance of bacteria at the firmicute level in the Pk and Dh treatments exhibited a significant increase of 83.22% and 82.19%, respectively, compared to the noninoculated reduced-salt dry sausage treatment (Cr). The relative abundance ofLatilactobacillus, especiallyL. sakei(0.46%, 2.80%, 65.88%, and 33.41% for the traditional dry sausage (Ct), Cr, Pk, and Dh treatments, respectively), increased significantly in the reduced-salt sausages inoculated with two yeast strains. Our work demonstrates the dynamic changes in the bacterial composition of reduced-salt sausages inoculated with different yeast strains, which could provide the foundation for the in-depth study of fungi–bacteria interactions in fermented foods.Keywords:reduced-salt dry sausage;yeast inoculation;bacterial composition;high-throughput sequencing
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