This work reports on a novel method for the determination of total acid (TA) in biomass hydrolysates by a solvent-assisted and reaction-based headspace gas chromatography (HS-GC). The neutralization reaction between the acids in hydrolysates and bicarbonate in an ethanol (50%) aqueous solution was performed in a closed headspace sample vial, from which the carbon dioxide generated from the reaction was detected by HS-GC. It was found that the addition of ethanol can effectively eliminate the precipitation of some organic acids in the biomass hydrolysates. The results showed that the reaction and headspace equilibration can be achieved within 45 min at 70 °C; the method has a good precision (RSD < 3.27%) and accuracy (recovery of 97.4–105%); the limit of quantification is 1.36 μmol. The present method is quite suitable to batch analysis of TA content in hydrolysate for the biorefinery related research.
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
In this study, the physicochemical properties and aroma characteristics of broad bean koji in the disk starter propagation system (DSPS) were studied by comparing with those in the incubator koji-making system (IKS) and the traditional koji-making system (TKS). The total acid content, amino acid nitrogen content, spore numbers and enzyme activities in the DSPS were significantly higher than those in the TKS and IKS. Among the 194 volatiles detected by GC×GC–MS in these three processes, 133, 159 and 123 appeared in DSPS, TKS and IKS, respectively. Fourteen volatiles were identified as aroma-active compounds by GC–O–MS, of which 10 compounds with OAVs greater than 1 were identified as key aromas. The koji qualities in different systems presented differences gradually with the incubation continuing by PCA analysis. The quantity of physicochemical properties associated with enzyme activity in the DSPS, IKS and TKS was 23, 17 and 22 respectively by the correlation analysis. The results indicated that a better quality of broad bean koji could be obtained in the DSPS.
危险品化学品经营许可证（带存储）