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To develop a unique flavor of rice wine, coffee flowers (by-products of the coffee industry) were added because of their biologically active compounds that are conducive to health, and the fermentation parameters were optimized. In addition, the dynamic changes of microbial communities and volatile flavor compounds (VFCs) during the different fermentation stages were investigated. After the optimization of the fermentation parameters, a novel product, i.e., the coffee flower rice wine (CFRW), was obtained with a bright yellow transparent, fragrant, and harmonious aroma and mellow and refreshing taste by sensory evaluation, when 4.62% of the coffee flowers and 1.93% koji were added and fermented at 24.10°C for 3.88 days. The results showed that Lactococcus was the dominant bacteria, accounting for 87.0–95.7%, while Rhizopus and Cladosporium were the main fungi, accounting for 68.2% and 11.3% on average, respectively, in the fermentation process of the CFRW. Meanwhile, twenty-three VFCs were detected in the CFRW, which included three alcohols, six terpenes, ten esters, three aromatics, and one furan. The correlation analysis revealed that there were 16 significant positive correlations and 23 significant negative correlations between the bacterium and VFCs (|ρ| > 0.6, p 0.6, p 0.6, p 0.6, p

Huangjinya has recently seen widespread adoption in key tea-producing areas of China, celebrated for its unique varietal traits. Its leaves are also used to produce black tea with distinctive sensory characteristics. The fragrance-enhancing (EF) process is essential in crafting Huangjinya black tea (HJYBT) and is significant in flavor development. However, the impact of EF on non-volatile metabolites (NVMs), volatile metabolites (VMs), and their interactions remains poorly understood. This study aims to investigate how EF temperatures (60 °C, 70 °C, 80 °C, 90 °C, and 110 °C) influence HJYBT flavor transformation. Quantitative descriptive analysis revealed that EF improved the color, aroma, and appearance of tea leaves. Moreover, after an EF temperature of 80 °C, the HJYBT exhibited lower bitterness and astringency, whereas floral, sweet, and fruity aromas became stronger. However, when EF temperatures exceeded 90 °C, a pronounced burnt aroma developed, with HJYBT at 100 °C exhibiting caramel and roasted notes. Partial least squares discriminant analysis indicated that geraniol and linalool contribute to floral and fruity aromas, while 2-ethyl-6-methyl-pyrazine, furfural, and myrcene are key volatiles for caramel and roast aromas. Heptanal, methyl salicylate, α-citral, 1-hexanol, and (E)-3-hexen-1-ol were found to modify the green and grassy odor. Overall, HJYBT treated at 80 °C EF exhibited the highest umami, sweetness, floral and fruity aromas, and overall taste, exhibiting the least astringency, bitterness, and green and grassy notes. These results provide a significant theoretical basis for enhancing HJYBT quality and selecting the optimal EF method.

Vinegar residue is a key secondary waste in the brewing industry that is often disposed irresponsibly, due to its large quantity and lack of reasonably effective use, causing environmental pollution issues. NaOH was used to pretreat Chinese vinegar residue, and the reaction products were consumed by the enzyme complex and Saccharomyces cerevisiae 1300 during the stage of simultaneous saccharification and fermentation (SSF). The results show that the optimal pretreatment conditions for Chinese vinegar residue were solid-to-liquid ratio of 1 : 11‏, NaOH concentration of 2.2%, pretreatment temperature of 63 °C, pretreatment time of 80 min, and amount of 4.9 IU g-1 xylanase. While these optimal conditions allowed more effective enzymatic degradation of the dried vinegar residue and resulted in the total sugar yield of 66.1%. Subsequently, dried vinegar residue and enzyme complex were added into the SSF process four times, and SSF reacted in a shaker at 120 r min-1 and 37 °C for 120 h, the yields of ethanol and xylose were 31.4% and 18.5%, respectively. Therefore, the method of Chinese vinegar residue for alcohol and xylose production by SSF was proved.

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.

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.

In order to reduce the environmental problems caused by vinegar residue emission, simultaneous saccharification and fermentation technology was used to produce alcohol and xylose from vinegar residue. Due to pretreatment of vinegar residue is vital for simultaneous saccharification and fermentation, uniform experimental designs were used to investigate each of the 5 factors involved in sodium hydroxide and xylanase pretreatment. The results showed that the optimal conditions for vinegar residue pretreatment were determined as solid-to-liquid ratio of 1:11(W/V), NaOH concentration of 2.2 %, pretreatment temperature of 71 °C, pretreatment time of 80 min and xylanase usage of 0.3 mL/g. Under this condition, the total sugar yield of vinegar residue was 664 mg/g. Following simultaneous saccharification and fermentation, alcohol and xylose were produced, the yields of ethanol and xylose were 319 mg/g and 179 mg/g, respectively. Therefore, the feasibility of producing alcohol and xylose by enzymatic degradation of vinegar residue was achieved. [ABSTRACT FROM AUTHOR]