Studies on the quality and flavor of ponkan (Citrus poonensis hort.) wines fermented by different yeasts

Effects of Non-Saccharomyces Yeasts and Their Pairwise Combinations in Co-Fermentation with Saccharomyces cerevisiae on the Quality of Chunjian Citrus Wine

Non-Saccharomyces (NSc) yeasts have great potential in improving wine qualities. In this study, two NSc and two Saccharomyces cerevisiae (Sc) samples were tested on their performance of mono-inoculated and composite culture in the fermentation of Chunjian citrus wine. The cell count, Brix degree, total sugar, total acidity, alcohol level, pH value, color intensity (CI), and tonality were determined to evaluate the contribution of NSc to the quality of citrus wine in the mixed fermentation. Volatile compounds were analyzed by HS-SPME-GC-MS, and sensory evaluation was carried out. During the 9-day fermentation, the mixed-culture wine exhibited a higher cell concentration than the pure culture. After the fermentation, mixed-culture wine specifically decreased the concentrations of unfavorable volatile compounds, such as isobutanol and octanoic acid, and increased favorable volatile compounds, including ethyl octanoate, ethyl decanoate, and phenylethyl acetate. The quality category of the citrus wine was improved compared with the Sc mono-inoculated wines, mainly in regard to aroma, retention, and sweetness. The study shows that the mixed fermentation of NSc and Sc has positive impacts on reducing alcohol level and total acidity and increasing CI. The present work demonstrates that the mixed fermentation of NSc and Sc has enormous beneficial impacts on improving the quality of citrus wine.

Effect of commercial yeasts (Saccharomyces cerevisiae) on fermentation metabolites, phenolic compounds, and bioaccessibility of Brazilian fermented oranges

Brazil is the largest producer of oranges worldwide, as well as one of the largest producers of orange juice. Alcoholic fermented beverages have been considered a marketable alternative for oranges. In this study, four S. cerevisiae commercial yeasts were evaluated for metabolites generated during orange juice (cv. 'Pêra D9') fermentation. Alcohols, sugars, and organic acids were evaluated by HPLC-DAD-RID during fermentation, and phenolic compounds were analyzed in fermented orange. Orange juice and fermented oranges were also subjected to digestion simulations. The yeasts presented an adequate fermentation activity, based on sugar consumption, and high ethanol (>10.5%) and glycerol (4.8-5.5 g/L) contents. The yeast strains T-58 and US-05 produced high levels of lactic acid. Phenolic compounds and antioxidant activity did not differ amongst yeasts, presenting hesperidin levels between 115 and 127 mg/L, respectively. The fermented orange showed a >70% bioaccessibility, compared to juice, especially for catechin, epigallocatechin-gallate, procyanidin-B2, rutin, and procyanidin-B1.

Effects of bio-augmented Daqu on microbial community, aroma compounds and physicochemical parameters of fermented grains during the brewing of Chinese special-flavor baijiu

BACKGROUND

Bio-augmented Daqu is used to improve the microbial community and physicochemical parameters of fermented grains, thus affecting the flavor and quality of baijiu. This study investigated the effects of bio-augmented Daqu inoculated with Aspergillus niger NCUF413.1 and Saccharomyces cerevisiae NCUF304.1 on the microbial community, aroma compounds, and physicochemical parameters of fermented grains during special-flavor baijiu brewing.

RESULTS

Compared with the control group (CG), the utilization of starch and production of ethanol in the inoculated group (IG) increased by 3.55% and 12.59%, respectively. The use of bio-augmented Daqu changed the bacterial communities. For example, Kroppenstedsia was the dominant bacterial genus (the relative abundance was about 22%) in the CG while Lactobacillus was the main dominant genus (the relative abundance was more than 30%) in the IG on days 20-30. Lactobacillus showed a significant positive correlation with the aroma compounds. The use of bio-augmented Daqu increased the aroma compound content - such as the ethyl heptanoate and ethyl hexanoate content.

CONCLUSION

The addition of bio-augmented Daqu with A. niger and S. cerevisiae could change microbial communities, resulting in an increase in the yield of ethanol and the aroma compound content of fermented grains, thus improving the quality of baijiu. © 2022 Society of Chemical Industry.

Incorporating Machine Learning in Computer-Aided Molecular Design for Fragrance Molecules

The demand for new novel flavour and fragrance (F&F) molecules has boosted the need for a systematic approach to designing fragrance molecules. However, the F&F-related industry still relies heavily on experimental approaches or on existing databases without considering the consequences resulting from changes in concentration, which could omit potential fragrances. Computer-aided molecular design (CAMD) has great potential to identify novel molecular structures to be used as fragrances. Using CAMD for this purpose requires models to predict the olfaction properties of molecules. A rough set-based machine learning (RSML) approach is used to develop an interpretable predictive model for odour characteristics in this work. New rule-based models are generated from RSML based on the dilution and a number of different topological indices which identify the structure-odour relationship of fragrance molecules. The most prominent rules are selected and formulated as constraints in a CAMD optimisation model. The combination of several rules was able to increase the coverage of different classes of molecules. To model the performance indicators that vary over a range of properties, a disjunctive programming model is also incorporated into the CAMD framework. A case study demonstrates the utilisation of this methodology to design fragrance additives in dishwashing liquid. The results illustrate the capability of the novel RSML and CAMD framework to identify potential fragrance molecules that can be used in consumer products.

Dynamic effects of fermentation on phytochemical composition and antioxidant properties of wampee (Clausena lansium (Lour.) Skeel) leaves

Variations in the phytochemical composition and antioxidant properties were studied in the wine of wampee leaves obtained at different stages of fermentation process. The highest concentrations of total phenolic and flavonoid contents were attained at Day 12 and Day 21 of fermentation, respectively. In addition, five phytochemical compounds including vanillic acid, p-coumaric acid, rutin, ferulic acid, and 7-hydroxycoumarin were identified and quantified by HPLC in fermented wampee products. The strongest antioxidant activity in wine was monitored on Day 12. Furthermore, total antioxidant activity was significantly correlated with vanillic acid, p-coumaric acid, ferulic acid, and 7-hydroxycoumarin compared with rutin. The obtained results suggested that 12-day fermentation could be an optimal process for excavation of applying wampee leaves into food and wine industries.