Sauvignon Blanc Research Articles

Smartphone-Based Leaf Colorimetric Analysis of Grapevine (Vitis vinifera L.) Genotypes

Leaf chlorophyll content is a key indicator of plant physiological status in viticulture; therefore, regular evaluation to obtain data for nutrient supply and canopy management is of vital importance. The measurement of pigmentation is most frequently carried out with hand-held instruments, destructive off-site spectrophotometry, or remote sensing. Moreover, smartphone-based applications also ensure a promising way to collect colorimetric information that could correlate with pigmentation. In this study, four grapevine genotypes were investigated using smartphone-based RGB (Red, Green, Blue) and CIE-L*a*b* colorimetry and a portable chlorophyll meter. The objective of this study was to evaluate the correlation between leaf chlorophyll concentration and RGB- or CIE-L*a*b*-based color indices. A further aim was to find an appropriate model for discriminating between the genotypes by leaf coloration. For these purposes, fully developed leaves of ‘Chardonnay’, ‘Sauvignon blanc’, and ‘Pinot noir’ clones 666 and 777 were investigated with the Color Grab smartphone application to obtain RGB and CIE-L*a*b* values. Using these color values, chroma, hue, and a further 31 color indices were calculated. Chlorophyll concentrations were determined using an Apogee MC100 device, and the values were correlated with color values and color indices. The results showed that the chlorophyll concentration and color indices significantly differed between the genotypes. According to the results, certain color indices show a different direction in their relationship with leaf pigmentation for different grapevine genotypes. The same index showed a positive correlation for the leaf chlorophyll concentration for one variety and a negative correlation for another, which raises the possibility that the relationship is genotype-specific and not uniform within species. In light of this result, further study of the species specificity of the commonly used vegetation indices is warranted. Support Vector Machine (SVM) analysis of the samples based on color properties showed a 71.63% classification accuracy, proving that coloration is an important ampelographic feature for the identification and assessment of true-to-typeness.

White wines aged in barrels with controlled tannin potential exhibit correlated long-term oxidative stability in bottle

Chardonnay and Sauvignon blanc wines aged in oak wood barrels with low and medium tannin potentials were discriminated for their abilities to resist against oxidation during bottle storage. The oak wood tannin potential was positively correlated to wines antioxidant capacity after 2 and 4 years of bottle aging. Untargeted molecular analysis revealed that the Sauvignon blanc metabolome was more affected by the tannin potential than the Chardonnay. Supervised statistical analysis highlighted the extensive oak wood contribution to the wine chemical fingerprints. Wines aged in barrel of medium tannin potential were associated with higher concentrations in antioxidant compounds such as dipeptides. Moreover, quantitative differences were observed between oak barrel derived volatile compounds. Sauvignon blanc volatile thiols appeared to decrease during bottle aging, regardless of the oak tannin potential. This study highlights the post bottling positive impact of oak wood barrel aging on wines oxidative stability, related to oak barrel tannin potential.

Chemometric Approach Application in Modern Wine Studies

The wine market is affected by the origin of wines, but the current wine traceability system has some limitations. The idea of geographical authenticity and quality has increased as one of the most important parameters influencing consumers’ preferences. Chemical parameters such as total polyphenolic content (TPC), alcohol and organic acid content (total acids, malic and tartaric acids), and antioxidant activity were observed in this work at 15 dry white wines of varieties Pinot blanc, Riesling, Sauvignon blanc, and Chardonnay, which originated from three different countries. FTIR and spectrophotometry methods (TPC and DPPH) were used and chemometric approaches such as ANOVA and PCA were selected as the most important for evaluation. In general, high levels of malic acid, TPC, and antioxidant activity were detected in Austrian wines. Pinot blanc, Chardonnay, and Sauvignon from the same producing region in Austria showed higher results. The higher overall acid concentration was a distinguishing feature of the Slovakian Sauvignon and Riesling varieties, particularly in the case of tartaric acid. Austrian samples showed significantly higher antioxidant activity compared to Hungarian Chardonnay (p = 0.002) and Sauvignon (p = 0.007), comparable to TPC. The application of statistical analysis was useful in demonstrating many discrepancies, particularly by application of the PCA method.

Comparison of pre-fermentation and post-fermentations alcohol adjustments on aromatic chemistry and sensory composition of Sauvignon blanc wine

Harvest and alcohol adjustment effects were evaluated for Sauvignon blanc grapes harvested at three potential alcohols (11, 13 and 15% (v/v)) by gas chromatography–mass spectrometry and descriptive analysis. Alcohol concentration was controlled for pre-fermentation by dilution or chaptalization and post-fermentation by dealcoholization. The initial experimental alcohol was treated as the control and the dealcoholized wine the treatment. Wine treatments sharing the same alcohol target and harvest date as the dealcoholized wine were designated as the negative control. All aroma compounds measured increased because of higher ethanol or declined because of dealcoholization. Similar aroma concentrations were observed to be a factor of alcohol concentration, apart from volatile thiols which were influenced by harvest. Statistical analysis of sensory and aroma compounds showed a corresponding relationship between low versus high alcohol wines. Dealcoholization appears to be an effective tool for altering wine aroma and winemaking style with comparable aroma loss to pre-fermentation adjustment.

The impact of simultaneous inoculation with Torulaspora delbrueckii and Hanseniaspora uvarum combined with Saccharomyces cerevisiae on chemical and sensory quality of Sauvignon blanc wines.

Non-Saccharomyces yeasts have great potential in improving wine quality, showing personality characteristics, and highlighting the terroir of wine. In this study, we evaluated the impact of simultaneous inoculation with the non-Saccharomyces yeasts Torulaspora delbrueckii or (and) Hanseniaspora uvarum in combination with Saccharomyces cerevisiae (EC1118 or VL3) on the aromatic compounds and sensory quality of Sauvignon blanc wines. The growth of yeast groups in the alcoholic fermentation process was tracked using fluorescence in situ hybridization. The presence of non-Saccharomyces yeast notably impacted the distribution of S. cerevisiae and was related to the species of yeast. The co-fermentation of H. uvarum and S. cerevisiae improved the content of total esters, especially acetate esters. Simultaneous inoculation of T. delbrueckii or (and) H. uvarum significantly increased the content of total terpenes, especially linalool. Similar results were found for some higher alcohols and organic acids. Sensory evaluation showed that the wines mixed fermentation with H. uvarum had significantly tropical fruit aroma characteristics. Citrus and mineral notes, typical aroma characteristics of Sauvignon blanc wine, were enhanced by mixed fermentation strategies with T. delbrueckii or (and) H. uvarum and different S. cerevisiae. Hence, co-fermentation by T. delbrueckii or H. uvarum combined with S. cerevisiae could significantly improve the sensory quality of Sauvignon blanc wine.

Effects of retained node numbers on berry maturity and yield components of cane-pruned Sauvignon blanc

Cane pruning is used in most New Zealand Sauvignon blanc vineyards to manage yield, vine balance (relationship between vegetative growth and fruit growth) and fruit primary and secondary metabolites. The source–sink ratio (TLA/FM—total leaf area to fruit mass or ELA/FM—exposed leaf area to fruit mass), the fruit mass to pruning mass (FM/PM), the fruit mass to cane mass (FM/CM) and fruit composition provide an assessment of the vine performance and balance. The interpretation of these metrics (i.e., TLA/FM, ELA/FM, FM/PM, FM/CM) requires their comparison with known optimal ranges specific to cultivars, locations and growing conditions. More often, such context- and cultivar-specific optimal ranges do not exist, thus warranting research to investigate them. To understand the influence of retained node numbers on the vegetative and fruit development of Sauvignon blanc, grapevines were pruned across three vineyard sites (two in Marlborough—Site 1 and 2, and one in Waipara—Site 3) over two growing seasons, retaining 10, 20, 30, 40 and 50 nodes on one to four canes (each cane carrying ten nodes, with 50-node vines carrying on average 12.5 nodes on each of the four canes). The accumulation of soluble solids (TSS) generally increased at lower node numbers and vine yields, reflecting an increase in ELA/FM, with 50-node vines having the least TSS concentration at harvest. The average berry mass, titrable acidity (TA) and pH were unaffected by node numbers over the two seasons. A low source–sink ratio induced by high node numbers not only reduced the vine capacity to ripen the current crop but also reduced the following season’s bunch number per shoot (from 1.8 to 1.6 bunches per shoot; p < 0.05), average bunch mass (from 82.0 ± 6 g to 67.7 ± 3 g; p < 0.01) and bunch mass per shoot (from 153.5 ± 15 g to 106.7 ± 9 g; p < 0.05). When compared to 50-node vines, 10-node vines had a two-fold increase in the average cane mass (from 30.1 ± 3.9 g to 69.2 ± 8.7 g; p < 0.001) and average old cane mass (from 82.4 ± 6.9 g to 163.8 ± 21 g; p < 0.001). The ELA/FM and TLA/FM required for optimal TSS accumulation were 0.75 m2 kg-1 and 2.0 m2 kg-1, respectively, across all sites. A source–sink ratio above these values resulted in high average cane mass and average old cane mass (an indication of excess vigour), while lower values indicated reduced vigour and slowed TSS accumulation. This research provides useful optimal ranges to compare and interpret vine balance metrics measured at those sites.

Bacterial-fungicidal vine disease detection with proximal aerial images

Vine disease detection is considered one of the most crucial components in precision viticulture. It serves as an input for several further modules, including mapping, automatic treatment, and spraying devices. In the last few years, several approaches have been proposed for detecting vine disease based on indoor laboratory conditions or large-scale satellite images integrated with machine learning tools. However, these methods have several limitations, including laboratory-specific conditions or limited visibility into plant-related diseases. To overcome these limitations, this work proposes a low-altitude drone flight approach through which a comprehensive dataset about various vine diseases from a large-scale European dataset is generated. The dataset contains typical diseases such as downy mildew or black rot affecting the large variety of grapes including Muscat of Hamburg, Alphonse Lavallée, Grasă de Cotnari, Rkatsiteli, Napoca, Pinot blanc, Pinot gris, Chambourcin, Fetească regală, Sauvignon blanc, Muscat Ottonel, Merlot, and Seyve-Villard 18402. The dataset contains 10,000 images and more than 100,000 annotated leaves, verified by viticulture specialists. Grape bunches are also annotated for yield estimation. Further, tests were made against state-of-the-art detection methods on this dataset, focusing also on viable solutions on embedded devices, including Android-based phones or Nvidia Jetson boards with GPU. The datasets, as well as the customized embedded models, are available on the project webpage.2

Managing Esca in Susceptible ‘Sauvignon Blanc’ Wine Grapes Through Trunk Renewal

Trunk renewal was evaluated as a treatment for highly susceptible ‘Sauvignon blanc’ wine grapes with moderate leaf and wood symptoms of the trunk disease Esca in a 17-year-old vineyard 7 years after symptoms first appeared. The trunk was cut above the graft union, removing all woody parts of the vine above it, including infected wood. A new trunk was retrained from a shoot off presumably healthy wood at the base of the trunk. Prior to trunk renewal, we detected Esca pathogens from 26% of 97 symptomatic vines. Five years after trunk renewal, 72 retrained vines were still asymptomatic, 24 were replanted (i.e., did not produce a shoot after trunk renewal), and one had leaf and fruit symptoms. Chemical composition of asymptomatic fruit from asymptomatic-retrained vines (RV-AF) was compared to that of vines that were not retrained, the latter of which included asymptomatic fruit from asymptomatic vines (AV-AF) and both asymptomatic fruit (SV-AF) and symptomatic fruit (SV-SF) from the same symptomatic vines. Given the high proportion of asymptomatic retrained vines after five growing seasons, trunk renewal was an effective cultural practice. Although there were no differences in chemistry parameters used to make harvest decisions (total soluble solids, pH, and titratable acidity), SV-SF was unique in having the highest concentrations of the flavonoids catechin and epicatechin and the lowest concentrations of the volatile-aroma compounds hexanal and 2-hexanal. These findings in all three blocks among fruit with visible spots may reflect a host-defense response and/or the effect of Esca on fruit ripening.

Targeting of Antifungal Metabolites from Grapevine Byproducts by UPLC-HRMS/MS Approaches Using Bioactivity-Based Molecular Networking.

This study focuses on countering Fusarium graminearum, a harmful fungal pathogen impacting cereal crops and human health through mycotoxin production. These mycotoxins, categorized as type B trichothecenes, pose significant health risks. Research explores natural alternatives to synthetic fungicides, particularly investigating phenolics in grapevine byproducts. Thirteen eco-extracts from five French grape varieties (Merlot, Cabernet Sauvignon, Sauvignon blanc, Tannat, and Artaban) exhibited substantial antifungal properties, with ten extracts displaying remarkable effects. Extracts from grapevine stems and roots notably reduced fungal growth by over 91% after five days. Through UHPLC-HRMS/MS analysis and metabolomics, the study identified potent antifungal compounds such as ampelopsin A and cyphostemmin B, among other oligomeric stilbenes. Interestingly, this approach showed that flavan-3-ols have been identified as markers for extracts that induce fungal growth. Root extracts from rootstocks, rich in oligostilbenes, demonstrated the highest antifungal activity. This research underscores grapevine byproducts' potential both as a sustainable approach to control F. graminearum and mycotoxin contamination in cereal crops and the presence of different metabolites from the cultivars of grapevine, suggesting different activities.

A Study of Condensates Collected during the Fermentation of Grape Must

This article deals with the analysis of the condensates which are formed from fermentation gases during the fermentation of grape must. The experiment was divided into two parts. In the first part, the evolution of the individual volatiles was monitored throughout the whole fermentation process of the Riesling variety. In the second part, the condensates from three different grape varieties (Riesling, Merlot, Sauvignon blanc) were investigated and the total content of the selected volatile substances was measured at the end of the fermentation. Attention was focused on the measurements using a GC-MS (gas chromatography-mass spectrometry) for the volatile substances: isoamyl alcohol, isobutyl alcohol, 1-propanol, ethyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, acetaldehyde, acetic acid, and acetoin. In addition, changes in the alcohol content of the condensate, with respect to the fermentation phase, were analysed. From the results of part 1, the quantity of the substances under investigation produced during fermentation was determined. The highest concentration of flavour compounds was during the fourth and fifth days of fermentation. The most dominant substance was isoamyl alcohol with a concentration of 1267 mg−1.The results of part 2 led to a comparison of the overall profile of volatiles between the varieties. The results showed that the condensates have both a high content of volatile substances and of alcohol. It was also shown that the Sauvignon blanc variant had the highest number of volatile compounds in the representation. The Merlot and Riesling variants were very similar. This product has an exceptionally high potential for further use in the wine or food industry.

Pre-Fermentative Cryogenic Treatments: The Effect on Aroma Compounds and Sensory Properties of Sauvignon Blanc and Chenin Blanc Wine—A Review

Low-temperature treatments preceding alcoholic fermentation are becoming increasingly popular and have been used in winemaking as a tool to improve wine colour, aroma, and quality. Additionally, the pre-fermentative treatment of grapes with cryogenic agents protects the grape juice (must) from oxidation by reducing the diffusion of atmospheric oxygen into the liquid phase during the winemaking process. Resultant wines were reported to have enhanced varietal aromas, increased complexity, and higher thiol levels. Indications are that increased contact time between skin and juice improves the extraction of the compounds and/or precursors. Recently, there has been considerable interest in the production of wines with enhanced varietal aromas and improved quality by applying innovative winemaking technologies. This review aims to provide an overview of the aroma and organoleptic quality of Sauvignon blanc and Chenin blanc wines produced from grapes that were subjected to pre-fermentative cryogenic treatments including the impact aroma compounds, i.e., volatile thiols and methoxypyrazines.

Logistic modeling of summer expression of esca symptoms in tolerant and susceptible cultivars in Bordeaux vineyards

The seasonal dynamics of esca leaf symptom development were monitored and modelled over 10 years (from 2004 to 2006, 2012 to 2014, and 2018 to 2021) in eleven vineyards near Bordeaux (France) and on five cultivars, including three susceptible and two tolerant Field observations performed once or twice a week from the end of May to mid-September confirmed i) the evolution over time of esca leaf symptoms, ii) the presence under the bark of a discolored xylem longitudinal stripe with nonfunctional vessels, and iii) a gradual increase in the number of symptomatic plants within each vineyard. Of the three models tested, nonlinear logistic regression was the best fitting curve, showing a clear and systematic progressive sigmoidal pattern of cumulative esca leaf symptom observations regardless of ‘vineyard*year’ situation. Relationships with climatic data confirmed that all periods of symptom expression corresponded to the warmest and driest period of each vegetative season. Examinations of key dates corresponding to four threshold levels of cumulative incidence of leaf symptomatic vines [S1 (first observed symptoms), S10 %, S50 % and S90 %] showed that tolerant cultivars (Merlot noir and Malbec) generally developed leaf symptoms later than susceptible cultivars (Cabernet-Sauvignon, Cabernet franc, and Sauvignon blanc). A variance analysis and a principal component analysis (PCA) confirmed that compared to susceptible cultivars, tolerant cultivars were associated with increased temperature sums above 10 °C from 1st January, reaching the same symptom thresholds S1 and S10 % and with more cumulative rainfall at the S1 stage. Overall, this study reveals the key role of temperature as a triggering factor for esca symptom expression in relation to fungal activity. The results indicate that the S10 % stage can be used as a discriminant variable to separate cultivars according to their susceptibility. Finally, logistic modelling can be used as a descriptive and analytical tool to study the seasonal dynamics of esca.

A machine learning-based electronic nose system using numerous low-cost gas sensors for real-time alcoholic beverage classification.

This study introduces numerous low-cost gas sensors and a real-time alcoholic beverage classification system based on machine learning. Dogs possess a superior sense of smell compared to humans due to having 30 times more olfactory receptors and three times more olfactory receptor types than humans. Thus, in odor classification, the number of olfactory receptors is a more influential factor than the number of receptor types. From this perspective, this study proposes a system that utilizes distinctive data patterns resulting from heterogeneous responses among numerous low-cost homogeneous MOS-based sensors with poor gas selectivity. To evaluate the performance of the proposed system, learning data were gathered using three alcoholic beverage groups including different aged whiskeys, Korean soju with 99% same compositions, and white wines made from the Sauvignon blanc variety, sourced from various countries. The electronic nose system was developed to classify alcoholic samples measured using 30 gas sensors in real time. The samples were injected into a gas chamber for 60 seconds, followed by a 60-second injection of clean air. After preprocessing the time-series data into four distinct datasets, the data were analyzed using a machine learning algorithm, and the classification results were compared. The results showed a high classification accuracy of over 99%, and it was observed that classification performance varied depending on data preprocessing. As the number of gas sensors increased, the prediction accuracy improved, reaching up to 99.83 ± 0.21%. These experimental results indicated that the proposed electronic nose system's classification performance was comparable to that of commercial electronic nose systems. Additionally, the implementation of an alcoholic beverage classification system based on a pretrained LDA model demonstrated the feasibility of real-time classification using the proposed system.

Long-term Effects of Irrigation with Treated Municipal Wastewater on Soil Chemical and Physical Responses in Commercial Vineyards in the Coastal Region of South Africa

The prolonged drought in the Western Cape province of South Africa in recent years has been particularly detrimental to the wine industry. Water restrictions imposed by authorities and the limited supply of fresh water that can be stored, have emphasisedthe need for alternative water sources for vineyard irrigation. Treated municipal wastewater has been used successfully as an alternative source of irrigation water in other countries. A long-term trial was conducted in commercial vineyards in the Coastal region of South Africa to assess the impact of treated municipal wastewater irrigation on vineyards. Cabernet Sauvignon and Sauvignon blanc grapevines were irrigated using treated municipal wastewater from the Potsdam wastewater treatment works for 11 years. Grapevines were either rainfed (RF), irrigated with treated municipal wastewater via a single dripper line (SLD), or received twice the volume of wastewater via a double dripper line (DLD). Irrigation using treated municipal wastewater increased soil pH(KCl), the electrical conductivity of the saturated extract (ECe) and Cl-. Substantial amounts of Na+ and K+ accumulated in the topsoil due to irrigation with treated municipal wastewater. These soil K+ increases could have a negative effect on wine colour stability should the levels of soil K+ be such that they are absorbed excessively by grapevines. The near-saturation hydraulic conductivity (Kns) at the surface of the soil could be related to the ECe in the topsoil. The results represent specific in-field situations in three commercial vineyards under one set of climatic conditions.

Research on the Determination of the Physicochemical and Sensory Characteristics of the Wine Produced by Malolactic Fermentation from Sauvignon Blanc, Merlot and Kalecik Karası Grapes

Objective: The aim of this study is to examine how malolactic fermentation and classical fermentation affect the physicochemical and sensory properties of wines made from red and white grapes.
 Methods: In our research, we opted for Sauvignon blanc variety in white grapes and locally produced Kalecik karası and French Merlot variety in red grapes all of which are recognised as important grape varieties both in our country and around the world. To preserve the natural aroma of the grape, start the fermentation rapidly and ensure formation of a balanced amount of glycerol, the use of Saccharomyces cerevisiae strain among vine yeasts deemed suitable. Oenoccus oeni MBR®UVAFERM®BETA (2x1011CFU/g) (Lallemand Inc., France) strain was used for malolactic fermentation. Sensory analyzes of the produced wines, chromatographic analysis of organic acids, and pysico-chemical analyses of products which are formed as a result of the processing of the fruits, were also made. For this purpose, the panelists evaluated the wines according to seven different criteria and the evaluation was made on a nine-point hedonic scale, and the most liked sample was given 9 points and the least liked one was given 1 point. Chemical and sensory properties of the produced wines were evaluated statistically.
 Results: As a result of our study, it has been determined that the amount of ash in red wines is higher which indicates higher amount of grape extracts obtained from Kalecik karası and Merlot grapes.When compared according to fermentation types, the amount of lactic acid increased in wines produced by malolactic fermentation whereas the amount of phenolic compounds was higher in ethyl alcohol concentrations, and these values decreased with malolactic fermentation. Additionally, the accommodation of two foreign origin grapes one of which is red and the other one white, country’s geography has been revealed in this study with the characteristics of the wine produced.
 Conclusion: The harmony of two foreign grapes, one red and one white grape, to the geography of our country was revealed with the characteristics of the wine produced. As a result of the thesis study, it was found that malolactic fermentation improved the quality of the wine, making it more pleasurable. In this context, the results of the research has the quality and attributes that will shed light on winemakers.

Mechanisms of grapevine resilience to a vascular disease: investigating stem radial growth, xylem development and physiological acclimation.

Plant vascular diseases significantly impact crop yield worldwide. Esca is a vascular disease of grapevine found globally in vineyards which causes a loss of hydraulic conductance due to the occlusion of xylem vessels by tyloses. However, the integrated response of plant radial growth and physiology in maintaining xylem integrity in grapevine expressing esca symptoms remains poorly understood. We investigated the interplay between variation in stem diameter, xylem anatomy, plant physiological response and hydraulic traits in two widespread esca-susceptible cultivars, 'Sauvignon blanc' and 'Cabernet Sauvignon'. We used an original experimental design using naturally infected mature vines which were uprooted and transplanted into pots allowing for their study in a mini-lysimeter glasshouse phenotyping platform. Esca significantly altered the timing and sequence of stem growth periods in both cultivars, particularly the shrinkage phase following radial expansion. Symptomatic plants had a significantly higher density of occluded vessels and lower leaf and whole-plant gas exchange. Esca-symptomatic vines showed compensation mechanisms, producing numerous small functional xylem vessels later in development suggesting a maintenance of stem vascular cambium activity. Stabilization or late recovery of whole-plant stomatal conductance coincided with new healthy shoots at the top of the plant after esca symptoms plateaued. Modified cropping practices, such as avoiding late-season topping, may enhance resilience in esca-symptomatic plants. These results highlight that integrating dendrometers, xylem anatomy and gas exchange provides insights into vascular pathogenesis and its effects on plant physiology.

Comparing defoliation and canopy sprays to delay ripening of Sauvignon blanc grapes

Higher temperatures caused by climate change are responsible for early maturation process which is often linked to low quality of grapes and wines. In this study, different canopy management techniques were tested and compared over three consecutive years (2017–19) with the aim to evaluate their capacity to delay ripening of Sauvignon blanc/SO4 grapes. These included a defoliation performed at veraison and the applications of antitranspirant (containing pinolene), kaolin and chitosan at bunch closure and veraison. The effects of the treatments on grapevine leaf gas exchanges, chlorophyll content and overall water status were measured during the three vegetative seasons. Moreover, soluble solids content and titratable acidity of berries were monitored from veraison until harvest, when final yield and berry composition were assessed. Pinolene transiently reduced the carbon assimilation rate and, independently from the growing season, significantly reduced sugar concentration in berries at harvest by -1.5°Brix as compared to the control. The defoliation reduced vine yield by 10–15 %, without significantly affecting total sugar and acid concentrations at harvest when compared to control. Kaolin and chitosan increased significantly berry acidity at harvest as compared to other treatments (i.e. defoliation and pinolene), but not to control. Under the temperate and rainy growing conditions of northeastern Italy, the antitranspirant product proved its potential as ripening retardant on a white grapevine cultivar. The high frequency of the rainfall events during the considered seasons partially hindered the full potential efficacy of the considered products sprayed to the canopy, questioning their overall efficacy under such conditions and mode of application.

Profiling the Bacterial Community of Fermenting Traminette Grapes during Wine Production using Metagenomic Amplicon Sequencing.

Advances in sequencing technology and the relatively easy access to the use of bioinformatics tools to profile microbial community structures have facilitated a better understanding of both culturable and non-culturable microbes in grapes and wine. During industrial fermentation, microbes, known and unknown, are often responsible for product development and off-flavor. Therefore, profiling the bacteria from grape to wine can enable an easy understanding of in situ microbial dynamics. In this study, the bacteria of Traminette grapes must undergoing fermentation, and the final wine were subjected to DNA extraction that yielded 15 ng/µL to 87 ng/µL. The 16S amplicon of the hypervariable region of the V4 region was sequenced, relatively abundant bacteria consisting of phyla Proteobacteria, Actinobacteriota, Firmicutes, Bacteroidota, Fusobacteriota and followed by the Verrucomicrobiota, Halobacterota, Desulfobacterota, Myxococcota, and Acidobacteriota. A Venn diagram analysis of the shared unique operational taxonomic units (OTU) revealed that 15 bacteria phyla were common to both grape must, fermenting stage, and final wine. Phyla that were not previously reported were detected using the 16S amplicon sequencing, as well as genera such as Enterobacteriaceae and Lactobacillaceae. Variation in the organic nutrient use in wine and its impact on bacteria was tested; Traminette R tank containing Fermaid O and Traminette L stimulated with Stimula Sauvignon blanc + Fermaid O. Alpha diversity using the Kruskal-Wallis test determined the degree of evenness. The beta diversity indicated a shift in the bacteria at the fermentation stage for the two treatments, and the final wine bacteria looked similar. The study confirmed that 16S amplicon sequencing can be used to monitor bacteria changes during wine production to support quality and better utilization of grape bacteria during wine production.

Physical Contact between Torulaspora delbrueckii and Saccharomyces cerevisiae Alters Cell Growth and Molecular Interactions in Grape Must

The use of multi-starters in oenological conditions (Saccharomyces cerevisiae and non-Saccharomyces species) is becoming increasingly common. For the past ten years, the combination of Torulaspora delbrueckii and S. cerevisiae has been proposed to winemakers to improve the wine aromatic profile compared to pure inoculation with Saccharomyces cerevisiae. In this work, two commercial strains, T. delbrueckii Zymaflore® Alpha and S. cerevisiae Zymaflore® X5 (Laffort compagny, Floirac, France), were investigated in Sauvignon blanc must using a fermentor with a double compartment allowing for physical separation of the two yeast species. The physical separation of the two species resulted in significant differences in the growth, fermentation kinetics (maximum fermentation rate (+13%)), fermentation duration (−14%) and the production of 3SH (+35%) in comparison to mixed cultures with contact. Proteomic analysis confirmed cell–cell contact interactions, as strong differences were observed for both species between mixed cultures with and without physical contact. T. delbrueckii mortality in mixed cultures with physical contact may be explained by an oxidative stress. Indeed two proteins implicated in the oxidative stress response were found in significantly higher amounts: a cytosolic catalase T and a cytoplasmic thioredoxin isoenzyme. For S. cerevisiae, an increase in proteins involved in the respiratory chain and proton transport were found in higher amounts in pure cultures and mixed culture without physical contact. Our results confirmed that the two mixed inoculations increased certain minor esters (ethylpropanoate, ethyl dihydrocinnamate and ethyl isobutanoate) specifically produced by T. delbrueckii, 3.4-fold more compared to in the pure S. cerevisiae culture. In conclusion, these results provide new insights into the underlying mechanisms involved in cell–cell contact and confirm the benefits of using T. delbrueckii species under winemaking conditions.

The Effect of Yeast Inoculation Methods on the Metabolite Composition of Sauvignon Blanc Wines

Evidence from the literature suggests that different inoculation strategies using either active dry yeast (ADY) or freshly prepared yeast cultures affect wine yeast performance, thus altering biomass and many primary and secondary metabolites produced during fermentation. Here, we investigated how different inoculation methods changed the fermentation behaviour and metabolism of a commercial wine yeast. Using a commercial Sauvignon blanc (SB) grape juice, fermentation was carried out with two different inoculum preparation protocols using Saccharomyces cerevisiae X5: rehydration of commercial ADY and preparation of pre-inoculum in a rich laboratory medium. We also determined the effect of different numbers of yeast cells inoculation (varying from 1 × 106 to 1 × 1012) and successive inoculation on fermentation and end-product formation. The yeast inoculation method and number of cells significantly affected the fermentation time. Principal component analysis (PCA) using 60 wine metabolites showed a separation pattern between wines produced from the two inoculation methods. Inoculation methods influenced the production of amino acids and different aroma compounds, including ethyl and acetate esters. Varietal thiols, 3-mercaptohexanol (3MH), and 4-methyl-4-mercaptopentan-2-one (4MMP) in the wines were affected by the inoculation methods and numbers of inoculated cells, while little impact was observed on 3-mercaptohexyl acetate (3MHA) production. Pathway analysis using these quantified metabolites allowed us to identify the most significant pathways, most of which were related to central carbon metabolism, particularly metabolic pathways involving nitrogen and sulphur metabolism. Altogether, these results suggest that inoculation method and number of inoculated cells should be considered in the production of different wine styles.