Liran Yang

Traditional fermented sausages are widely consumed in China but often face quality and safety risks due to contamination by spoilage and pathogenic microorganisms during natural fermentation. This study investigated the effect of Litsea cubeba essential oil (LCEO) on the microbial community structure and volatile flavor compounds (VFCs) of fermented sausages using multi-omics approaches, including 16S/ITS amplicon sequencing and HS-SPME-GC-MS. The results showed that LCEO significantly altered the microbial community, increasing the relative abundance of Lactobacillus from 4.65% to 76.22% and Debaryomyces from 11.95% to 22.35%, while reducing Staphylococcus and Aspergillus by 47.01% to 4.55% and 37.28% to 17.09%, respectively. A total of 695 VFCs were identified, with terpenoids and hydrocarbons being the most abundant. A differential analysis revealed that LCEO enhanced the relative content of key aroma-active compounds, including ethyl esters and aldehydes, with odor activity values exceeding 1 for fruity-related compounds such as decanoic acid, ethyl ester and nonanoic acid, methyl ester. Strikingly, the elevated levels of these fruity esters translated into significantly higher sensory scores for odor (p < 0.05) in LCEO-treated sausages, as panelists consistently perceived a pronounced fruity and fresh aroma profile, ultimately leading to a superior overall acceptability compared to the control. A correlation analysis indicated strong positive associations between Lactobacillus, Debaryomyces, and major flavor-contributing esters. In conclusion, LCEO potentially reduces the microbial risks and improves the flavor profile of fermented sausages, making it a promising natural additive for meat fermentation.

Developing an effective method to achieve stability and improve the quality of Tibetan tea has scientific significance. Aspergillus niger K1 isolated and identified from Tibetan tea was inoculated in unsterilized or sterilized tea leaves to develop the bioaugmented fermentation (BF) and normal fermentation (NF) processes of Tibetan tea. The results showed that BF resulted in infusions with a deeper color, a stronger aroma, and a thicker taste compared to NF. The dominant bacterium in BF was Staphylococcus (23.76%), while the dominant fungus was Blastobotrys adeninivorans (50.95%). Moreover, 859 metabolites were identified, and the level of 90 differentially changed metabolites (DCMs) in BF increased significantly (VIP > 1, p < 0.05, FC > 2) compared to those in NF, while the level of 37 DCMs in BF decreased significantly (VIP > 1, p < 0.05, FC < 0.5). Correlation analysis demonstrated that A. niger significantly positively correlated with theabrownins, caffeine, and glutamylisoleucine (p < 0.05, |r| > 0.8). B. adeninivorans showed significant negative correlations with 1-(beta-D-ribofuranosyl)-1,4-dihydronicotinamide and 2-hydroxyacetaminophen sulfate (p < 0.05, |r| > 0.8). Consequently, the inoculation of A. niger for BF has the potential to alter the metabolites in tea through a synergistic interaction with other microorganisms, ultimately improving the sensory quality of Tibetan tea.

Sichuan black tea (SCBT) is well known for its pleasant sweet and citrus-like aroma. However, the origin of this distinctive aroma remains unknown. Herein, the aroma characteristics of SCBT during processing were comprehensively investigated by sensory evaluation, gas chromatography–mass spectrometry, and odor activity value (OAV). A total of 764 volatile compounds were identified and grouped into 16 categories. Notably, terpenoids, heterocyclic compounds, and esters comprised 19.35%, 16.34%, and 16.08% of total volatile compounds produced during processing, respectively. Moreover, the fermentation and second drying stages exhibited the most striking variations, with 99 and 123 volatile compounds being significantly altered. In addition, the OAV analysis led to the identification of 17 volatile compounds as key differential volatile compounds (DVCs): these included citronellol, linalool, p-cymene, (E)-linalool oxide (furanoid), etc. Among them, (3Z)-3,7-dimethylocta-1,3,6-triene and D-limonene that exhibited a grassy aroma decreased during processing, while linalool and p-cymene that had a sweet and citrus aroma increased. Thus, based on a correlation between characteristic aroma data and descriptive sensory analysis data, linalool and p-cymene were identified as the primary volatiles responsible for the sweet and citrus-like aroma. In conclusion, this study improves our understanding of the components and formation mechanism of the sweet and citrus-like aroma of SCBT.