Impact of fermentation temperature and grape solids content on the chemical composition and sensory profiles of Cabernet Sauvignon wines made from flash détente treated must fermented off-skins

Characterization of chemical and sensory properties of Cabernet Sauvignon and Marselan wines made by flash détente technique

This study aimed to characterize the sensory profiles of wines produced using the flash détente (FD) technique and to identify the flavor compounds contributing to the sensory characteristics. The FD technique was applied to two major grape varieties, Cabernet Sauvignon and Marselan, from the Changli region of China to produce high-quality wines with aging potential. Compared to the traditional macerated wines, the FD wines showed greater color intensity, mainly due to the higher levels of anthocyanins. Regarding the aroma characteristics, FD wines were found to have a more pronounced fruitness, especially fresh fruit note, which was due to the contribution of higher concentration of esters. Concurrently, FD wines showed an increased sweet note which was associated with increased lactones and furanones. In addition, FD wines exhibited reduced green and floral notes due to lower levels of C6 alcohols and C13-norisoprenoids. With regard to mouthfeel, FD wines presented greater astringency and bitterness, which was due to the higher levels of phenolics. The total concentration of condensed tannins and condensed tannins for each degree of polymerization was considerably higher in FD wines due to the strong extraction of the FD technique. A significant increase in grape-derived polysaccharides and glycerol was also found in FD wines, contributing to a fuller body. This study contributed to an increase in the knowledge of the Changli region and demonstrated that the FD technique could be applied to the wine production in this region to address the negative impacts of rainfall in individual vintages.

A mutant GH3 family β-glucosidase from Oenococcus oeni exhibits superior adaptation to wine stresses and potential for improving wine aroma and phenolic profiles

In this study, we conducted a comprehensive investigation into a GH3 family β-glucosidase (BGL) from the wild-type strain of Oenococcus oeni and its mutated counterpart from the acid-tolerant mutant strain. Our analysis revealed the mutant BGL's remarkable capacity to adapt to wine-related stress conditions, including heightened tolerance to low pH, elevated ethanol concentrations, and metal ions. Additionally, the mutant BGL exhibited superior hydrolytic activity towards various substrates. Through de novo modeling, we identified specific amino acid mutations responsible for its resilience to low pH and high ethanol environments. In simulated wine conditions, the mutant BGL outperformed both wild-type and commercial BGLs, efficiently releasing terpene and phenolic aglycones from glycosides in wine grapes. These findings not only expand our understanding of O. oeni BGLs but also highlight their potential in enhancing wine production. The mutant BGL's enhanced adaptation to wine stress conditions opens promising avenue for improving wine quality and flavor.

Enhanced Expression of Alcohol Dehydrogenase I in Pichia pastoris Reduces the Content of Acetaldehyde in Wines

Acetaldehyde is an important carbonyl compound commonly detected in wines. A high concentration of acetaldehyde can affect the flavor of wines and result in adverse effects on human health. Alcohol dehydrogenase I (ADH1) in Saccharomyces cerevisiae catalyzes the reduction reaction of acetaldehyde into ethanol in the presence of cofactors, showing the potential to reduce the content of acetaldehyde in wines. In this study, ADH1 was successfully expressed in Pichia pastoris GS115 based on codon optimization. Then, the expression level of ADH1 was enhanced by replacing its promoter with optimized promoters and increasing the copy number of the expression cassette, with ADH1 being purified using nickel column affinity chromatography. The enzymatic activity of purified ADH1 reached 605.44 ± 44.30 U/mg. The results of the effect of ADH1 on the content of acetaldehyde in wine revealed that the acetaldehyde content of wine samples was reduced from 168.05 ± 0.55 to 113.17 ± 6.08 mg/L with the addition of 5 mM NADH and the catalysis of ADH1, and from 135.53 ± 4.08 to 52.89 ± 2.20 mg/L through cofactor regeneration. Our study provides a novel approach to reducing the content of acetaldehyde in wines through enzymatic catalysis.

Effect of fermentation temperature on oenological parameters and volatile compounds in wine

The increase in temperature caused by climate change is one of the greatest challenges the wine industry has to face. Temperature increase affects sugar and alcohol content, which directly impact the chemical and organoleptic characteristics of wine. This has a serious impact on the competitiveness and profits of companies in the sector. Among the most studied strategies focused on guaranteeing wine quality is the use of yeast strains that are better adapted to the conditions generated by climate change. Therefore, this study seeks to evaluate whether the Saccharomyces cerevisiae strains LALVIN CY3079 and UVAFERM WAM maintain their organoleptic characteristics at different temperatures. For this purpose, 3 experimental fermentations were carried out at 16, 20, and 27ºC, respectively. Alcoholic fermentation was monitored (pH, sugars, and microbial population) and general oenological parameters (acetic, citric, malic, succinic, lactic, amine nitrogen, ammonium, and glycerol) were evaluated at the beginning and end of fermentation. In addition, the ethanol content and volatile compounds formed at the end of fermentation were analysed. As a result of these experimental fermentations, it was observed that most of the basic oenological parameters and volatile compounds are modified as a function of fermentation temperature.

Use of Microwave Maceration in Red Winemaking: Effect on Fermentation and Chemical Composition of Red Wines

The objective of this study was to evaluate the effect of microwave treatment of crushed grapes on the yeast population of the must and on the development of alcoholic fermentation, as well as on the extraction of different compounds from the grapes such as polysaccharides and amino acids that can affect the organoleptic quality and stability of the wine. This study demonstrated for the first time the effect of the microwave treatment of grapes on native yeast species and their diversity, producing an increase in fermentation kinetics and a decrease in the lag phase. The microwave treatment produced a positive effect on the extraction of amino acids and polysaccharides from the grapes, resulting in significantly higher amounts of the main amino acids of the must and some major volatile compounds in the treated samples. The polysaccharides most affected by the microwave treatment were the PRAGs, the main polysaccharides liberated from grapes during the maceration.