Effects of different fermentation and storage conditions on methanol content in Chinese spine grape (Vitis davidii Foex) wine

Comprehensive Analysis of Physicochemical Properties and Volatile Compounds in Different Strawberry Wines under Various Pre-Treatments

Pre-fermentation treatment has an important impact on the color, aroma, taste, and other characteristics of fruit wine. To discover suitable pre-treatment techniques and conditions that yield strawberry wine of excellent quality, the influences of juice fermentation, pulp maceration, thermovinification, and enzymatic hydrolysis pre-treatments on the basic chemical composition, color, antioxidant capacity, and volatile organic compounds in strawberry wines were investigated. The results showed that the color, antioxidant properties, and volatile aroma of strawberry wines fermented with juice were different from those with pulp. Strawberry wines fermented from juice after 50 °C maceration had more desirable qualities, such as less methanol content (72.43 ± 2.14 mg/L) compared with pulp-fermented wines (88.16 ± 7.52 mg/L) and enzymatic maceration wines (136.72 ± 11.5 mg/L); higher total phenolic content (21.78%) and total flavonoid content (13.02%); enhanced DPPH (17.36%) and ABTS (27.55%) free radical scavenging activities; richer essential terpenoids and fatty acid ethyl esters, such as linalool (11.28%), ethyl hexanoate (14.41%), ethyl octanoate (17.12%), ethyl decanoate (32.49%), and ethyl 9-decenoate (60.64%); pleasant floral and fruity notes compared with juice-fermented wines macerated at normal temperatures; and a lighter color. Overall, juice thermovinification at 50 °C is a potential pre-treatment technique to enhance the nutrition and aroma of strawberry wine.

Oenological potential of wines produced from disease-resistant grape cultivars

Within the EU, changes in policy and public sentiment have made it more urgent to consider the adoption of sustainable agricultural practices. Consequently, one of the EU's goals is to reduce pesticide use by 50 per cent by 2030, including in viticulture. One of the proposed approaches is to expand the use of disease resistant hybrid grape-cultivars (DRHGC), such as 'PIWI' grapes (German, Pilzwiderstandsfähige Rebsorten), and to introduce new DRHGCs. However, the characteristics of DRHGCs are different from those of Vitis vinifera, which makes it necessary to take measures and make changes in winemaking technology to maintain high wine quality. This paper examines the chemistry of wines made from DRHGC and discusses their impact on aroma and flavor profiles. It also reviews the main winemaking practices suggested to produce high-quality wines from DRHGCs. The chemistry of DRHGCs is different to wine produced from V. vinifera, which can lead to both challenges during winemaking and unusual flavor profiles. Although newer DRHGCs have been bred to avoid unexpected flavors, many DRHGCs are still rich in proteins and polysaccharides. This can make tannin extraction difficult and produce wines with little astringency. In addition to this, new or alternative winemaking techniques such as thermovinification and the use of alternative yeast strains (non-Saccharomyces) can be used to produce wines from DRHGCs that are acceptable to consumers.

Endogenous CO2 Overpressure Effect on Higher Alcohols Metabolism during Sparkling Wine Production

Higher alcohols produced by yeast during the fermentation of sparkling wine must have the greatest impact on the smell and taste of wine. At present, the metabolic response to methanol and higher alcohols formation of Saccharomyces cerevisiae under endogenous CO₂ overpressure has not been fully elucidated. In this work, a proteomics and metabolomics approach using a OFFGEL fractionator and the LTQ Orbitrap for the protein identification, followed by a metabolomic study for the detection and quantification of both higher alcohols (GC-FID and SBSE-TD-GC-MS) and amino acids (HPLC), was carried out to investigate the proteomic and metabolomic changes of S. cerevisiae in relation to higher alcohols formation under a CO₂ overpressure condition in a closed bottle. The control condition was without CO₂ overpressure in an open bottle. Methanol and six higher alcohols were detected in both conditions, and we have been able to relate to a total of 22 proteins: 15 proteins in the CO₂ overpressure condition and 22 proteins in the control condition. As for the precursors of higher alcohols, 18 amino acids were identified in both conditions. The metabolic and proteomic profiles obtained in both conditions were different, so CO₂ overpressure could be affecting the metabolism of higher alcohols. Furthermore, it was not possible to establish direct correlations in the condition under CO₂ overpressure; however, in the condition without pressure it was possible to establish relationships. The data presented here can be considered as a platform that serves as a basis for the S. cerevisiae metabolome-proteome with the aim of understanding the behavior of yeast under conditions of second fermentation in the production of sparkling wines.

Effect of light-selective sunshade net on the quality and aromatic characteristics of Cabernet Sauvignon grapes and wine: Exploratory experiment on strong solar irradiance in northwestern China

The greenhouse effect is a global problem. In view of the intense sunlight radiation in Ningxia (an ideal wine-producing region in northwestern China), the effect of light-selective sunshade nets of different colors (black, red and white) on the quality and aromatic characteristics of grapes and wine was studied. With the treatments of different nets, the solar radiation intensity was significantly decreased. The sugar contents in both grapes and wines decreased, while the acid contents increased. The contents of total phenols, tannins and flavanols in grapes were increased, while the total flavonoids and anthocyanins were decreased. The contents of most phenolics in wine were increased. The contents of most aromas in grapes and wines under nets were higher than those in the control group. The black group usually possessed the highest variety and content. Red and black nets improved the fruity, floral and sweet aromas of grapes. The white net decreased the green and citrusy aromas.

Screening low-methanol and high-aroma produced yeasts for cider fermentation by transcriptive characterization

The commercial active dry yeast strains used for cider production in China are far behind the requirements of the cider industry development in recent decades. In this study, eight yeasts, including Saccharomyces cerevisiae, Schizosaccharomyces pombe, Pichia bruneiensis, and Pichia kudriavzevii, were screened and assessed by growth performance, methanol production, aroma analysis, and their transcriptive characterization. Saccharomyces cerevisiae strains WFC-SC-071 and WFC-SC-072 were identified as promising alternatives for cider production. Strains WFC-SC-071 and WFC-SC-072 showed an excellent growth capacity characterized by 91.6 and 88.8% sugar utilization, respectively. Methanol production by both strains was below 200 mg/L. Key aroma compounds imparting cider appreciably characteristic aroma increased in cider fermented by strains WFC-SC-071 and WFC-SC-072. RT-qPCR analysis suggested that most genes associated with growth capacity, carbohydrate uptake, and aroma production were upregulated in WFC-SC-071 and WFC-SC-072. Overall, two Saccharomyces cerevisiae strains are the optimal starters for cider production to enable the diversification of cider, satisfy the differences in consumer demand, and promote cider industry development.

Learning from 80 years of studies: a comprehensive catalogue of non-Saccharomyces yeasts associated with viticulture and winemaking

Non-Saccharomyces yeast species are nowadays recognized for their impact on wine´s chemical composition and sensorial properties. In addition, new interest has been given to the commercial exploitation of non-Saccharomyces starter cultures in the wine sector. However, over many years, these yeast species were considered sources of contamination in wine production and conservation, mainly due to the high levels of volatile acidity obtained. The present manuscript systematizes 80 years of literature describing non-Saccharomyces yeast species isolated from grapes and/or grape musts. A link between each reference, the accepted taxonomic name of each species and their geographical occurrence is presented, compiling information for 293 species, in a total of 231 citations. One major focus of this work relates to the isolation of non-Saccharomyces yeasts from grapevines usually ignored in most sampling studies, also as isolation from damaged grapes. These particular niches are sources of specific yeast species, which are not identified in most other explored environments. These yeasts have high potential to be explored for important and diversified biotechnological applications.