Effect of training systems on fatty acids and their derived volatiles in Cabernet Sauvignon grapes and wines of the north foot of Mt. Tianshan

Whole-field mulching and removal indicated the flavonoid plasticity in Marselan grapes and wines: Insights from the metabolome and transcriptome

As an eco-friendly vineyard floor management, mulching can effectively control weeds, preserve soil moisture, reduce irrigation requirements, and modify the grapevine microclimate. However, its impact on the grapevine microclimate, as well as the variation in grape and wine flavonoids across different growth stages under mulching conditions remains insufficiently studied. Therefore, in the vineyard of a semi-arid region, the whole-field mulching (M) of black geotextile mulch was applied to Vitis vinifera Marselan grapevines from anthesis and removed at three phenological stages. The grape and wine flavonoids during the growing season were evaluated through HPLC-MS, and the transcriptomic data was analyzed in three vintages (2015-2017). Results showed that mulching weakened over 30°% of reflected light, and especially light with longer wavelengths. Mulching helped to reduce water evaporation and lead to higher soil water content. As for berry composition, M slightly decreased the berry weight and accelerated sugar accumulation when mulch removal. Controlled grapes presented higher flavonols at harvest while mulch removal around veraison enhanced the accumulation of anthocyanins. The reflected photosynthetic active radiation, cluster temperature, and soil moisture played important roles in flavonoid regulation. Key genes including VviFLS1, VviLAR1, and VviANR, as well as MYB transcription factors MYBF1, MYBA1, and MYB3 are responsible for flavonoid regulation. M slightly affected the wine flavor profile but improved the wine's appearance. In conclusion, M effectively suppresses weed growth and modifies grapevine microclimate in semi-arid climates, mulch removal around veraison favored the accumulation of grape flavonoids.

Effects of Mountain-Basin System on Chemical Composition, Antioxidant Activity and Volatile Flavor Substances of Cabernet Sauvignon Wines in Xinjiang Region, China

To investigate the effect of mountain-basin system on wine quality, four different regions were selected according to altitude and latitude. This work analyzed the differences in physicochemical properties, organic acids, monomeric phenols, antioxidant activity and volatile compounds of Cabernet Sauvignon wine between four regions. Comparative analysis revealed that there were significant differences in alcohol content and pH, respectively. Malic acid in organic acids was the main acid to distinguish the four regions. Correlation analysis showed that there was a significant correlation between physicochemical properties and climatic conditions in the four regions. There were significant differences in most of the monomeric phenols, and the antioxidant capacity was also significantly different. A total of 60 volatile compounds were detected, including 11 key volatile compounds, and there were significant differences in the composition of wines in the four regions. Methyl salicylate, ethyl caprate and ethyl hexanoate were the characteristic aromas in mountain front (MF) and intermontane basin (IB) regions, decanal was the characteristic aroma in sloping field (SF) region, and ethyl butyrate was the characteristic aroma in near desert (ND) region. This study further clarified the influence of climate and terrain on wine quality, and provided a better theoretical basis for the fine management of small producing areas.

Transcriptomic profiling reveals a regulatory network governing volatile compound biosynthesis in Shine Muscat grapes (Vitis labruscana Baily × V. vinifera L.)

MAIN CONCLUSION

Winter berries accumulated more free volatile compounds than summer berries, and C6 volatile compounds were the main contributors to free volatile compounds. The volatile composition of grapes and wines is important in viticulture, since their aroma is one of the most important determinants of grape fruit quality. The aroma and general quality of grape fruit are influenced by the production of volatile compounds primarily influenced by crop management. In this study, the free and bound volatile compounds were determined using gas chromatography-mass spectrometry (GC-MS), along with the transcriptomic analysis using Shine Muscat grape (Vitis labruscana Baily × V. vinifera L.) of summer and winter berries under two-crop-a-year cultivation in Guangxi. The findings demonstrated that phenols, terpenoids, and alcohols were the main bound volatile compounds in fruits from both seasons, whereas aldehydes, terpenoids, and alcohols were the leading free volatile compounds. Free volatile compound concentrations were substantially higher in winter than summer berries, but bound volatile compound concentrations were much lower. Specifically, the concentrations/constitution of free C6 volatile compounds showed a significant difference between the two seasons and highly correlated with the transcription of three genes involved in the lipoxygenase (LOX) pathway. Winter berries had a higher concentration of aldehydes, which might be ascribed to the higher expression of VvLOXA (VIT_06s0004g01510) and VvHPL1 (VIT_12s0059g01060) genes, while the higher concentration of alcohols in summer berries might be due to the higher expression of alcohol dehydrogenase (VvADH1, VIT_18s0001g15410). Furthermore, two VvBGLU genes (VIT_05s0077g01150, VIT_01s0011g00760) were supposed to regulate the enzymatic hydrolysis of glycoside-bound compounds in grapes. Three transcription factors including MYB60, MYBA1, and GATA16 were highly correlated with VvADH1, and they might play an important role in grape C6 alcohol biosynthesis. The findings may help to reveal a transcriptional regulation network of volatile compounds biosynthetic in grapes and to develop efficient cultivation practices.

Advancements and challenges for brewing aroma-enhancement fruit wines: Microbial metabolizing and brewing techniques

Aroma, a principal determinant of consumer preference for fruit wines, has recently garnered much attention. Fruit wines brewing was concomitant with complex biochemical reactions, in which a variety of compounds jointly contribute to the aroma quality. To date, the mechanisms underlying the synthesis of aroma compounds and biological regulation methods in fruit wines have remained ambiguous, hindering the further improvement of fruit wines sensory profiles. This review provides a detailed account of the synthesis and regulatory mechanisms of typical aroma compounds and their contributions to the characteristics of wines. Additionally, Comprehensive involves between microflora and the formation of aroma compounds have been emphasized. The microflora-mediated aroma compounds evolution can be controlled by key fermentation techniques to protect and enhance. Meanwhile, the genes impacting key aroma compounds can be identified, which provide references for the rapid screening of aroma-enhanced strains as well as target formation of aroma by modifying relative genes.

Influences of Cluster Thinning on Fatty Acids and Green Leaf Volatiles in the Production of Cabernet Sauvignon Grapes and Wines in the Northwest of China

Cluster thinning has been widely applied in yield management and its effect on green leaf volatiles (GLVs) in wines has seldom been studied. GLVs are important flavor compositions for grapes and wines. This work aimed to investigate the impact of cluster thinning on these volatiles and their precursors in grapes and wines. Severe cluster thinning (CT1) and medium cluster thinning (CT2) were performed on Cabernet Sauvignon (Vitis vinifera L.) vines in two sites (G-farm and Y-farm) from Xinjiang province in the Northwest of China. The impact of cluster thinning treatments on the accumulation of GLVs and their precursors, long chain fatty acids (LCFAs) of grape berries and C6 volatiles, in resulting wines was investigated. Multivariate analysis showed that cluster thinning treatments induced significant changes in fruit and wine composition in both farms. In Y-farm, medium cluster thinning (CT2) significantly increased the average cluster weight of harvested berries. Additionally, both cluster thinning treatments (CT1 and CT2) increased fatty acids in harvested berries and CT2 led to an increase in C6 esters and a decrease in C6 alcohols in the wines of Y-farm under the warmer and drier 2012 vintage. However, the effect of cluster thinning was likely negative in G-farm due to its wetter soil and excessive organic matter. The treatments may be applicable for local grape growers to improve viticultural practices for the more balanced vegetative and reproductive growth of Cabernet Sauvignon grapevines. This work also provided further knowledge on the regulation of fatty acids and the derived C6 volatiles through the lipoxygenase (LOX) pathway.

Comparative Analysis of the Evolution of Green Leaf Volatiles and Aroma in Six Vitis vinifera L. Cultivars during Berry Maturation in the Chinese Loess Plateau Region

Green leaf volatiles (GLVs) are important in giving grape a fresh and green aroma. But the changes in GLVs during the phenological development of grapevines are not well known. This study analyzed the GLVs and transcription levels of associated biosynthetic genes in six grape species from the Loess Plateau region at five stages of maturation. Thirteen GLVs were detected, showing unique patterns for each grape type at various growth phases. The primary components in six grapes were (E)-2-hexenal, (E)-2-hexen-1-ol, and hexanal. With the exception of Cabernet Franc in 2019, the overall GLV contents of the six types generally increased during growth and development, peaking or stabilizing at harvest. And Sauvignon Blanc, Cabernet Gernischt, and Cabernet Sauvignon exhibited higher total contents among the varieties. PLS-DA analysis revealed 3-hexenal's high VIP scores across two years, underscoring its critical role in grape variety classification. Correlation analysis revealed a strong positive correlation between the levels of hexanal, 1-hexanol, (E)-2-hexen-1-ol, (Z)-3-hexenyl acetate, nonanal, and (E, E)-2,6-nonadienal and the expression of VvHPL and VvAAT genes in the LOX-HPL pathway. Specifically, VvHPL emerges as a potential candidate gene responsible for species-specific differences in GLV compounds. Comprehending the changing patterns in the biosynthesis and accumulation of GLVs offers viticulturists and enologists the opportunity to devise targeted strategies for improving the aromatic profile of grapes and wines.

Application of benzothiadiazole to Cabernet Gernischt grapes (Vitis vinifera L.) for quality improvement: Effects on aroma metabolism precursors and related genes expression

Pre-harvest spraying of benzothiadiazole (BTH) can improve the winemaking properties of grapes, especially their aroma compounds and phenolics. Limited research has explored the molecular mechanisms by which BTH influences the accumulation of grape aroma precursors during early grape development. This study investigated the effects and putative molecular mechanisms of applying 0.37 mM BTH through whole-plant spraying on the accumulation of aroma metabolism precursors and gene expression in Cabernet Gernischt grapes during ripening. The results showed that BTH treatment increased the levels of fructose, alanine, aspartate, threonine, myristic acid, myristoleic acid, palmitic acid, β-cryptoxanthin, norisoprenoids and methoxypyrazines. Contrarily, it decreased the levels of glucose, sucrose, phenylalanine, tyrosine, leucine, valine, glycine, arginine, histidine, total unsaturated fatty acids (particularly linoleic acid), zeaxanthin, lutein, and organic acids. Additionally, BTH upregulated the expression of genes associated with the production and degradation of amino acids, fatty acids, and carotenoids while decreasing the expression of genes involved in the synthesis and degradation of soluble sugars and organic acids. Ten different metabolites, including fumaric acid, were identified as potential biological markers for distinguishing BTH-treated grapes from control grapes. The study demonstrates that BTH treatment had a substantial impact on the concentration and developmental patterns of aroma metabolism precursors. Furthermore, it altered the winemaking characteristics of Cabernet Gernischt grapes by modulating genes associated with the production and breakdown of metabolites.

Integrated Transcriptomic and Proteomic Analysis Identifies Novel Regulatory Genes Associated with Plant Growth Regulator-Induced Astringency in Grape Berries

Astringency influences the sensory characteristics and flavor quality of table grapes. We tested the astringency sensory attributes of berries and investigated the concentration of flavan-3-ols/proanthocyanidins (PAs) in skins after the application of the plant growth regulators CPPU and GA3 to the flowers and young berries of the "Summer Black" grape. Our results showed that CPPU and GA3 applications increase sensory astringency perception scores and flavan-3-ol/proanthocyanidin concentrations. Using integrated transcriptomic and proteomic analysis, differentially expressed transcripts and proteins associated with growth regulator treatment were identified, including those for flavonoid biosynthesis that contribute to the changes in sensory astringency levels. Transient overexpression of candidate astringency-related regulatory genes in grape leaves revealed that VvWRKY71, in combination with VvMYBPA1 and VvMYC1, could promote the biosynthesis of proanthocyanidins, while overexpression of VvNAC83 reduced the accumulation of proanthocyanidins. However, in transient promoter studies in Nicotiana benthamiana, VvWRKY71 repressed the promoter of VvMYBPA2, while VvNAC83 had no significant effect on the promoter activity of four PA-related genes, and VvMYBPA1 was shown to activate its own promoter. This study provides new insights into the molecular mechanisms of sensory astringency formation induced by plant growth regulators in grape berries.

Influence of Benzothiadiazole on the Accumulation and Metabolism of C6 Compounds in Cabernet Gernischt Grapes (Vitis vinifera L.)

Pre-harvest application of elicitors improves grape quality, specifically the phenolic compounds and color characteristics. Limited research has been conducted on the impact of elicitors on the C6 compounds found in grapes. This is due to lack of comprehensive studies examining the combined effects of bound aroma compounds, enzyme activity, and substrate availability. This study aimed to assess the impact of benzothiadiazole (BTH) on the physicochemical properties and C6 compounds of Cabernet Gernischt grapes during ripening. Compared with the control group (CK), BTH treatment significantly increased the 100-berry weight, skin/berry ratio, pH, total phenolic content, and total flavonoid content in ripe grapes. Additionally, BTH treatment led to significant reductions in reducing sugar, total soluble solids, titratable acidity, linoleic acid, linolenic acid, and free C6 aldehydes. Furthermore, BTH treatment significantly decreased the contents of free C6 alcohols and increased the levels of free and bound C6 esters. BTH treatment also increased the activities of lipoxygenase, alcohol dehydrogenase, and alcohol acetyltransferase enzymes, while it decreased the activity of hydroperoxide lyase enzyme. The application of BTH resulted in changes to the physicochemical properties and levels of C6 compounds in Cabernet Gernischt grapes by up-regulating enzyme activity and down-regulating precursors.

Evolution of green leaf volatile profile and aroma potential during the berry development in five Vitis vinifera L. Cultivars

Green leaf volatiles (GLVs), play important roles in the green and fresh aroma characteristics of grape berries. The evolution of GLV profiles regarding the varietal difference during grapevine phenological ripening is not well understood. This study generated the GLV profiles of five Vitis vinifera L. cultivars ('Cabernet Sauvignon,' 'Cabernet Franc,' 'Cabernet Gernischt,' 'Chardonnay,' and 'Sauvignon Blanc') at five ripening stages. GLVs were distinctive at different E-L stages for each grape variety. (E)-2-hexen-1-ol, 1-hexanol, and hexanal were the dominant components in all mature berries. In terms of total GLV content, all varieties reached the maximum at maturity in the 2019 vintage, and the total GLV content was higher in mature Sauvignon Blanc and Cabernet Sauvignon grapes. In the 2020 vintage, the total GLV content in Chardonnay and Sauvignon Blanc berries rapidly accumulated at veraison and peaked before harvest. The present results could help winemakers create a good balance of wine aroma.

The influence of light microclimate on the lipid profile and associated transcripts of photosynthetically active grape berry seeds

Lipids and oils determine the quality and industrial value of grape seeds. Studies with legume seeds demonstrated the influence of light on lipid metabolism and its association with seed photosynthesis. Grape berry seeds are photosynthetically active till mature stage, but mostly during the green stage and veraison. The objective of this work was to compare the lipid profiles of seeds from white grape berries (cv. Alvarinho) growing at two contrasting light microclimates in the canopy (low and high light, LL and HL respectively), previously reported to have distinct photosynthetic competences. Berries were collected at three developmental stages (green, veraison and mature) and from both microclimates, and the seeds were analyzed for their lipid profiles in an untargeted manner using liquid chromatography coupled to high resolution mass spectrometry (LCMS). The seed lipid profiles differed greatly among berry developmental stages, and to a lesser extend between microclimates. The LL microclimate coincided with a higher relative levels of fatty acids specifically at mature stage, while the HL microclimate led to an up-regulation of ceramides at green stage and of triacylglycerols and glycerophospholipids at mature stage. The seed transcript levels of four key genes (VvACCase1, VvΔ9FAD, VvFAD6 and VvLOXO) involved in fatty acid metabolism were analyzed using real-time qPCR. The lipoxygenase gene (VvLOXO) was down- and up-regulated by HL, as compared to LL, in seeds at green and veraison stages, respectively. These results suggest that seed photosynthesis may play distinct roles during seed growth and development, possibly by fueling different lipid pathways: at green stage mainly towards the accumulation of membrane-bound lipid species that are essential for cell growth and maintenance of the photosynthetic machinery itself; and at veraison and mature stages mainly towards storage lipids that contribute to the final quality of the grape seeds.

Investigating Grapevine Red Blotch Virus Infection in Vitis vinifera L. cv. Cabernet Sauvignon Grapes: A Multi-Omics Approach

Grapevine red blotch virus (GRBV) is a recently identified virus. Previous research indicates primarily a substantial impact on berry ripening in all varieties studied. The current study analyzed grapes’ primary and secondary metabolism across grapevine genotypes and seasons to reveal both conserved and variable impacts to GRBV infection. Vitis vinifera cv. Cabernet Sauvignon (CS) grapevines grafted on two different rootstocks (110R and 420A) were analyzed in 2016 and 2017. Metabolite profiling revealed a considerable impact on amino acid and malate acid levels, volatile aroma compounds derived from the lipoxygenase pathway, and anthocyanins synthesized in the phenylpropanoid pathway. Conserved transcriptional responses to GRBV showed induction of auxin-mediated pathways and photosynthesis with inhibition of transcription and translation processes mainly at harvest. There was an induction of plant-pathogen interactions at pre-veraison, for all genotypes and seasons, except for CS 110R in 2017. Lastly, differential co-expression analysis revealed a transcriptional shift from metabolic synthesis and energy metabolism to transcription and translation processes associated with a virus-induced gene silencing transcript. This plant-derived defense response transcript was only significantly upregulated at veraison for all genotypes and seasons, suggesting a phenological association with disease expression and plant immune responses.

Volatile Composition of Sparkling Wines of cv. Chardonnay Cultivated under Different Training Systems in Serra da Mantiqueira (Brazil)

The grapevine is a climbing plant and allows for the manipulation of vegetative canopies to change the microclimate and exposure of leaves and clusters to solar radiation, affecting the primary and secondary metabolisms of plants. Thus, this work aimed to evaluate how the lyre and Geneva double-curtain (GDC) training systems could contribute to the volatile composition of sparkling wines in replicates of vinifications carried out in the Serra da Mantiqueira (Brazil) in two consecutive summer harvests (2017 and 2018). Fifty-four free volatile compounds were identified by HS-SPME/GC-MS in the wines in both systems and vintages. Multivariate analysis differentiated the vintages in component 1 (22.7%) and the training systems in component 2 (7.1%). The crops were differentiated by aldehydes in 2017 and in 2018 by isoamyl acetate ester, probably derived from the amino acid leucine, the season having been more humid, with lower temperatures and less radiation. For the training systems, besides the alcohol compounds, the GDC was differentiated by the terpenoid compounds geranylacetone and β-damascenone, which may contribute more pleasant aromas to sparkling wines. This work promotes additional research and enables winegrowers, through the management of their vineyards, to achieve sparkling wines with different volatile compositions.

Effect of Early Basal Leaf Removal on Phenolic and Volatile Composition and Sensory Properties of Aglianico Red Wines

The aim of this work was to study the influence of early basal leaf removal on Aglianico wines produced in the Apulia region (Italy). Three treatments were carried out, where 100% of fruit-zone leaves on the north (DN), south (DS) and on both sides of the canopy (DNS) were removed. A control (CT), where all basal leaves were retained, was also performed. Instrumental (HPLC-DAD-MS and GC-MS) and sensory analysis (QDA) were used to evaluate the treatment effect on the phenolic and volatile compositions and on the sensory descriptors of wines. DNS reached the highest amounts of phenolic compounds, showing a change in the phenolic pattern from flavonols and anthocyanins. Moreover, leaf removal influenced the levels of 37.8% of volatile compounds, quantified by increasing the concentration when early leaf removal was applied on the north side of the canopy (DN), with respect to the south (DS) and both sides (DNS). In the sensory analysis, Aglianico wines were defined by 16 sensory attributes with GM > 30%, where the highest values were reached for defoliation treatments vs. control. In conclusion, early leaf removal treatments allowed us to modulate the phenolic and volatile concentrations of Aglianico wines.

Training grapevines generates a metabolomic signature of wine

Training systems are an option to handle the pronounced apical dominance of grapevines and to influence diverse traits of the corresponding wine. However, it is still unclear if different training systems generate signatures in the metabolome of the wine. By an untargeted metabolomics approach using (SPME) GC-MS wine (volatiles) and leaves were evaluated. Different training directions such as vertical shoot positioning systems, hanging shoot systems, and minimal pruning systems were distinguishable in wine. It was shown, that different training systems generate a metabolomic signature in the wine which was more pronounced than in leaves. Moreover, the sensory analysis showed some changes in the aroma of the different training systems. Thus, the influence of the training system ranges from the leaf metabolome to the wine metabolome.

Characterization and Evolution of Volatile Compounds of Cabernet Sauvignon Wines from Two Different Clones during Oak Barrel Aging

Xinjiang is a major wine-making region in China, but its hot climate in summer and intense sun exposure negatively affect the aroma quality of Cabernet Sauvignon wine. The aim of this study was to characterize and differentiate the volatile composition of Cabernet Sauvignon wines from two clones (169 and 191) in Xinjiang, and to study their aromatic profile evolution during 12-month oak barrel aging period. Results showed that before aging, clone 169 wine contained higher concentrations of several alcohols and ethyl esters, while acetate esters and furanic compounds were higher in clone 191 wine. After aging, levels of many terpenes, norisoprenoids, volatile phenols and phenolic aldehydes were significantly higher in clone 169 wine than 191 wine. Aroma series analysis revealed that clone 169 wine exhibited higher floral and roasty aromas after aging, while clone 191 wine had stronger chemical aroma. Principal component analysis indicated that aging process played a primary role in the alteration of volatile profile in these wines. Clone played a secondary role and oak barrel had a tertiary contribution to the variation. The present work indicates that clone 169 is a better choice for producing high-quality aged Cabernet Sauvignon wine with intense and elegant aroma in Xinjiang.

Effect of Soil Management and Training System on Negroamaro Wine Aroma

This study aimed to assess the impact of two soil managements and training systems on yield and wine aroma compounds of Negroamaro variety grown in a warm climate region (southern Italy). Cover crop (CC) and soil tillage (ST) as soil management, whilst bilateral Guyot (BG) and monolateral Guyot (MG) as training systems were compared. Free and bound volatile fractions were evaluated by GC-MS. ST and CC as well as BG and MG significantly affected yield parameters. In particular, yield was higher in ST and BG than in CC and MG, respectively; moreover, it was found to be positively influenced by interaction between BG and ST. Regarding aroma compounds, significant interactions between soil management and training system factors were observed. In case of free volatiles, the most positive interaction was found between BG and ST, whereas, for bound volatiles, the best interaction was represented by MG with both soil tillage and cover crop. Vine leaf area and development over vine growth stages along with water stress levels played an important role in determining the aroma profile as well as yield parameters. In conclusion, the training system significantly interacted with soil management and affected most of important aroma compounds in Negroamaro wine.

Effect of the Seasonal Climatic Variations on the Accumulation of Fruit Volatiles in Four Grape Varieties Under the Double Cropping System

The double cropping system has been widely applied in many subtropical viticultural regions. In the 2-year study of 2014-2015, four grape varieties were selected to analyze their fruit volatile compounds in four consecutive seasons in the Guangxi region of South China, which had a typical subtropical humid monsoon climate. Results showed that berries of winter seasons had higher concentrations of terpenes, norisoprenoids, and C6/C9 compounds in "Riesling," "Victoria," and "Muscat Hamburg" grapes in both of the two vintages. However, in the "Cabernet Sauvignon" grapes, only the berries of the 2014 winter season had higher terpene concentrations, but lower norisoprenoid concentrations than those of the corresponding summer season. The Pearson correlation analysis showed the high temperature was the main climate factor that affected volatile compounds between the summer and winter seasons. Hexanal, γ-terpinene, terpinen-4-ol, cis-furan linalool oxide, and trans-pyran linalool oxide were all negatively correlated with the high-temperature hours in all of the four varieties. Transcriptome analysis showed that the upregulated VviDXSs, VviPSYs, and VviCCDs expressions might contribute to the accumulations of terpenes or norisoprenoids in the winter berries of these varieties. Our results provided insights into how climate parameters affected grape volatiles under the double cropping system, which might improve the understanding of the grape berries in response to the climate changes accompanied by extreme weather conditions in the future.

Characterization of free and glycosidically bound volatile compounds, fatty acids, and amino acids in Vitis davidii Foex grape species native to China

Berries of six Vitis davidii Foex (spine grape) cultivars ('Baiputao', 'Gaoshan 1', 'Gaoshan 2', 'Seputao', 'Miputao', and 'Tianputao') were harvested from a commercial vineyard in Hunan Province in China. Free and bound volatile compounds and fatty acids were analyzed by GC-MS, and amino acids were analyzed by HPLC. 'Tianputao' and 'Miputao' were characterized by relatively higher concentrations of aromatic amino acids and lower concentrations of branched-chain amino acids. The major free volatile compounds of spine grapes were hexanal, (E)-2-hexenal, 1-hexanol, (E)-2-hexenol, (E)-β-damascenone, and benzeneacetaldehyde. The major glycosidically bound volatile compounds identified were 1-hexanol, menthol, nerol, 1-butanol, 3-methyl-3-butenol, benzenemethanol, β-phenylethanol, eugenol, and guaiacol. (E)-β-damascenone, benzeneacetaldehyde, guaiacol, and eugenol had odor activity values (OAVs) > 1 in all cultivar grapes. Partial least squares discriminant analysis (PLS-DA) revealed 'Tianputao' to be distinct from the other cultivars due to its relatively higher concentrations of major terpenoids, norisoprenoids, higher alcohols, and aromatic amino acids.

Modulation of volatile compound metabolome and transcriptome in grape berries exposed to sunlight under dry-hot climate

BACKGROUND

Basal leaf removal is widely practiced to increase grape cluster sunlight exposure that controls berry rot and improves quality. Studies on its influence on volatile compounds in grape berries have been performed mostly in Mediterranean or marine climate regions. It is uncertain whether similar efficiency can be achieved when grape berries are grown under continental climate. This study aimed to dissect the variation in volatile compound production and transcriptome in sunlight-exposed grape berries in a dry-hot climate region and to propose the key genes related to the variation.

RESULTS

Four cluster sunlight exposure strategies, including basal leaf removal at pepper-corn size stage, leaf removal at véraison (LR-V), leaf moving at véraison (LM-V), and half-leaf removal at véraison, were implemented at the north foot of the Mt. Tianshan region of northwestern China. Various cluster exposure treatments resulted in a decline in the concentrations of norisoprenoids and monoterpenes in ripening grape berries. Both β-carotene and lutein, the substrates of norisoprenoid biosynthesis, were reduced by cluster sunlight exposure. K-means cluster analysis showed that some genes involved in biosynthesis such as VviTPS55, VviTPS60, VviTPS66, VviCCD4a and VviCCD4b exhibited lower expression levels in exposed berries at least at one of the tested stages. Two C6-derived esters with fruity attributes, ethyl hexanoate and hexyl acetate, were reduced markedly. In contrast, main C6 alcohol compound levels were elevated in the LR-V- and LM-V-treated grape berries, which corresponded to the up-regulated expression of VviLOXA, VviLOXO and VviADH1 in the oxylipin pathway. Most of the differentially expressed genes in the exposed and control berries were enriched to the "stress response" processes, and this transcriptome difference was accumulated as the berries matured. Besides, LR-V treatment stimulated a significant up-regulation in photosynthesis-related genes in the grape berries, which did not happen with LM-V treatment.

CONCLUSIONS

Cluster sunlight exposure in dry-hot climate viticulture resulted in different volatile-targeted transcriptomic and metabolic responses from those obtained in the temperate Mediterranean or marine climate region. Therefore, a modified canopy management should be adopted to improve the aroma of grape berries.

Impact of Drying Method on the Evaluation of Fatty Acids and Their Derived Volatile Compounds in 'Thompson Seedless' Raisins

Air- and sun-dried raisins from Thompson Seedless (TS) grapes were analyzed under GC/MS to evaluate fatty acids (FAs) and their derived volatile compounds, coming from unsaturated fatty acids oxidation. A total of 16 FAs were identified in TS raisins, including 10 saturated fatty acids (SFAs) and 6 unsaturated fatty acids (USFAs). The contents of C18:0, C15:0, and C16:0 among SFAs and C18:3, C18:2 and C18:1 in USFAs were significantly higher. Furthermore, USFAs such as C16:1 and C20:1 were only identified in air-dried raisins. The principal component analysis showed the increased content of FAs and FA-derived compounds were in air-dried and sun-dried raisins, respectively. Among FA-derived compounds, 2-pentyl furan, 3-octen-2-one, 1-hexanol and heptanoic acid were more potent. This study shows that air-drying is more favorable for the production of fatty acids (SFAs and USFAs), whereas sun-drying is more advantageous in terms of fatty acid-derived volatiles.

Transcriptional Comparison Investigating the Influence of the Addition of Unsaturated Fatty Acids on Aroma Compounds During Alcoholic Fermentation

The levels of unsaturated fatty acids (UFAs) in grape must significantly influence yeast metabolism and the production of aroma compounds. In this work, cDNA microarray technology was applied to analyze the transcriptional discrepancies of wine yeast (commercial wine yeast Lalvin EC1118) fermenting in synthetic grape must supplemented with different concentrations of a mixture of UFAs (including linoleic acid, oleic acid, and α-linolenic acid). The results showed that the initial addition of a high level of UFAs can significantly enrich the intracellular UFAs when compared to a low addition of UFAs and further increase the cell population and most volatiles, including higher alcohols and esters, except for several fatty acids. Microarray analyses identified that 63 genes were upregulated, and 91 genes were downregulated during the different fermentation stages. The up-regulated genes were involved in yeast growth and proliferation, stress responses and amino acid transportation, while the repressed genes were associated with lipid and sterol biosynthesis, amino acid metabolism, TCA cycle regulation, mitochondrial respiration, and stress responses. Unexpectedly, the genes directly related to the biosynthesis of volatile compounds did not vary substantially between the fermentations with the high and low UFA additions. The beneficial aromatic function of the UFAs was ascribed to the increased biomass and amino acid transportation, considering that the incorporation of the additional UFAs in yeast cells maintains high membrane fluidity and increases the ability of the cells to resist deleterious conditions. Our results highlighted the importance of UFAs in the regulation of aroma biosynthesis during wine fermentation and suggested that the improvement of the resistance of yeast to extreme stresses during alcoholic fermentation is essential to effectively modulate and improve the production of aroma compounds. A potential way to achieve this goal could be the rational increase of the UFA contents in grape must.

Use of Indigenous Hanseniaspora vineae and Metschnikowia pulcherrima Co-fermentation With Saccharomyces cerevisiae to Improve the Aroma Diversity of Vidal Blanc Icewine

Using novel non-Saccharomyces strains is regarded as an effective way to improve the aroma diversity of wines to meet the expectations of consumers. The non-Saccharomyces Hanseniaspora vineae and Metschnikowia pulcherrima have good aromatic properties useful for the production of table wine. However, no detailed information is available on their performances in icewine fermentation. In this study, simultaneous and sequential fermentation trials of indigenous M. pulcherrima CVE-MP20 or H. vineae CVE-HV11 with S. cerevisiae (SC45) were performed in 50-L fermenters of Vidal icewine, respectively. The results showed that SC45 cofermented with different non-Saccharomyces strains could generate a distinct aroma quality of icewine compared with four S. cerevisiae strain monocultures as evidenced by principal component analysis (PCA). Mixed fermentation of MP20/SC45 produced higher contents of acetate esters and β-damascenone with lower C₆ alcohols relative to SC45 monoculture. Interestingly, HV11/SC45 generated the highest amounts of C₆ alcohols [(Z)-3-hexen-1-ol and (E)-3-hexen-1-ol], higher alcohols (isobutanol, isopentanol, and 2-phenylethanol), acetate esters (2-phenethyl acetate and isoamyl acetate), cis-rose oxide, β-damascenone, and phenylacetaldehyde. Compared with simultaneous inoculation, sequential inoculation could achieve higher aroma diversity and produce higher intensity of fruity, flowery, and sweet attributes of icewine as assessed by calculating the odor activity values (OAVs). Our results verified the desired enological characteristics of H. vineae strain in icewine fermentation and also demonstrated that using indigenous non-Saccharomyces and Saccharomyces strains is a feasible way to improve aroma diversity of icewine products, which could provide an alternative way to meet the requirement of wine consumers for diversified aromatic quality.

Use of Torulaspora delbrueckii Co-fermentation With Two Saccharomyces cerevisiae Strains With Different Aromatic Characteristic to Improve the Diversity of Red Wine Aroma Profile

The use of selected Saccharomyces and non-Saccharomyces strains as mixed starters has advantages over pure fermentation due to achieving wine products with distinctive and diversified aroma expected by consumers. To obtain a way to improve the aroma diversity and increase the differentiation of wine product, in this study, the aromatic effect of multi-culture of indigenous Torulaspora delbrueckii (TD12), simultaneous and sequential inoculation with two Saccharomyces strains (indigenous icewine yeast SC45 and commercial yeast BDX) with different enological characteristics were investigated in laboratory-scale 20 L fermenter, respectively. The results showed that T. delbrueckii co-fermented with different S. cerevisiae strain could generate diversified physicochemical and aromatic quality of wine as evidenced by PCA. Mixed fermentation of SC45/TD12 produced higher contents of higher alcohol (3-methyl-1-pentanol and phenylethyl alcohol), ethyl esters (ethyl decanoate and ethyl butanoate), terpenes and phenylacetaldehyde with less fatty acids (hexanoic acid, octanoic acid) and acetic acid, while BDX/TD12 generated more C₆ alcohol (1-hexanol) and acetate esters (ethyl acetate and isoamyl acetate). Compared to simultaneous inoculation, sequential inoculation could achieve higher aroma diversity, and generate higher intensity of fruity, flowery and sweet attributes of wine as assessed by calculating the odor activity values. The different S. cerevisiae strain and inoculation method in alcoholic fermentation could further influence the formations of aromatic compounds in malolactic fermentation. Our results highlighted the importance of S. cerevisiae strain in shaping the aromatic quality of wine in mixed fermentation, and also suggested that using different S. cerevisiae strains with distinct aromatic characteristics co-fermentation with specific non-Saccharomyces strain is a potential way to increase the aromatic diversity and quality of wine product, which could provide an alternative way to meet the requirement of wine consumers for diversified aromatic quality.

Effects of Basal Defoliation on Wine Aromas: A Meta-Analysis

Basal defoliation, as one of the most common viticulture management practices to modify fruit zone microclimates, has been widely applied aiming at improving wine quality. Wine aroma contributes greatly to wine quality, yet the effects of basal defoliation on wine aromas show discrepancies according to previous studies. This study is a meta-analysis performed to dissect the factors related to the influence of basal defoliation on volatile compounds in wine. Timing of basal defoliation plays an important role in the concentration of varietal aromas in wine. Pre-veraison defoliation induces an increase in β-damascenone and linalool as well as a reduction in 3-isobutyl-2-methoxypyrazine (IBMP). The effects of basal defoliation on certain volatile compounds relative to fermentation aromas in wine (1-hexanol, β-phenylethanol, 2-phenylethyl acetate, decanoic acid, and ethyl octanoate) depend on grape maturity. There are also other factors, such as cultivar and climate conditions, that might be responsible for the effect of basal defoliation on wine aromas. The concentrations of isobutanol, isoamyl alcohol, hexanoic acid, and octanoic acid as well as ethyl isobutyrate, ethyl hexanoate, ethyl isovalerate, and ethyl decanoate in wine are not markedly affected by basal defoliation. Due to limited studies included in this meta-analysis, more trials are needed to confirm the current findings.

Effects of simple rain-shelter cultivation on fatty acid and amino acid accumulation in 'Chardonnay' grape berries

BACKGROUND

Fatty acids and amino acids are the precursors of aliphatic and aromatic volatile compounds, higher alcohols and esters. They are also nutrition for yeast metabolism during fermentation. However, few reports have been concerned about the effect of viticulture practices on the accumulation of fatty acids and amino acids in wine grapes. This study aimed to explore the accumulation of these compounds in developing Vitis vinifera L. cv. Chardonnay grape berries under two vintages, and compare the influences of the rain-shelter cultivation and open-field cultivation.

RESULTS

Fifteen fatty acids and 21 amino acids were detected in total. The rain-shelter cultivation led to an increase in the total concentration of fatty acids, and a decrease in the total concentration of amino acids compared with the open-field cultivation in 2012, while no significant difference was observed between two cultivation modes in 2013 vintage. Concentrations of palmitoleic acid, isoleucine and cysteine were significantly promoted in the rain-shelter grape berries, whereas those of tyrosine and ornithine were markedly reduced in both vintages.

CONCLUSION

The rain-shelter cultivation of wine grapes in the rainy region is beneficial for improving grape quality and fermentation activity by influence on the concentration of fatty acids and amino acids. © 2017 Society of Chemical Industry.

Differential Expression of VvLOXA Diversifies C6 Volatile Profiles in Some Vitis vinifera Table Grape Cultivars

C6 volatiles are synthesized through lipoxygenase-hydroperoxide lyase (LOX-HPL) pathway and these volatiles play important roles in the aromatic quality of grape berries. This study investigated the evolution of both C6 volatiles and the key genes in the LOX-HPL pathway in different table grape cultivars during the berry development period, and further assessed the correlation between the accumulation of C6 volatiles and the expression of these genes in these cultivars. Results showed that hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol and (Z)-3-hexen-1-ol were found to be the dominant C6 volatiles in these ripened grape cultivars under two consecutive vintages, and their flavor notes were incorporated in the overall aroma of these cultivars. The cultivar "Xiangfei" showed the most abundant level of C6 aldehydes and C6 acid, whereas the cultivar "Tamina" and "Moldova" possessed the highest C6 alcohol content. The "Muscat of Alexandria" cultivar was found to contain the highest level of C6 esters. C6 volatiles were grouped into three evolutionary patterns in these cultivars during berry development, and their evolution was consistent with the evolution of the LOX-HPL pathway genes' expression. Pearson's correlation analysis indicated that the LOX-HPL-pathway-related genes were correlated to the accumulation of C6 volatiles in these cultivars, and VvLOXA appeared to be an important gene that regulated the synthesis of all C6 volatiles.

Comprehensive and comparative lipidome analysis of Vitis vinifera L. cv. Pinot Noir and Japanese indigenous V. vinifera L. cv. Koshu grape berries

Vitis vinifera cv. Koshu is an indigenous grape cultivar that has been cultivated for more than a thousand years in Japan and one of the most important cultivars in white winemaking. To improve Koshu wine quality, it is necessary to identify the metabolites in Koshu berry. We conducted a comprehensive and comparative lipidome analysis of Koshu and Pinot Noir berries cultivated in the same location in Japan using GC-MS/MS for fatty acids and LC-MS for glycerolipids and glycerophospholipids. Koshu skins and juices contained 22 and 19 fatty acids, respectively, whereas 23 and 20 fatty acids were detected in Pinot Noir skins and juices. C22:6n3 and C24:0 contents in Koshu skins were two and three times higher than those in Pinot Noir skins. C24:0 content in Koshu juices was also higher than that in Pinot Noir juices. Forty-nine lipid components (six digalactosyldiacylglycerols, one monogalactosyldiacylglycerol, 10 phosphatidylcholines, 12 phosphatidylethanolamines, and 20 triglycerides) were detected in Pinot Noir and Koshu skins. Strong peaks were observed for MGDG 36:6, DGDG 36:6, PC 34:2, PC 36:5, TG 54:6, TG 54:7, and TG 54:8 in Koshu skins. The contents of 36 of the 49 lipid components were significantly higher in Pinot Noir skins than Koshu skins. Pinot Noir skins contained more lipids whose alkyl chains have more than 18 carbons than Koshu skins. Further analysis of both lipid profiles revealed that the number of double bonds in a fatty acid molecule in Pinot Noir skins and juices was significantly larger than that in Koshu skins and juices. A strong relationship exists between the heat requirement of grapevine cultivars and the level of fatty acid desaturation. C18-fatty acids were the major components in Koshu and Pinot Noir berries. The expression levels of C18-fatty acid desaturases regulated the accumulation of C18-unsaturated fatty acids in berry skins. The loss of C18:3 in Koshu berries at the end of ripening was observed. Koshu might effectively convert C18:3 into (Z)-hex-3-enal for the production of C6-aroma compounds. These findings by the lipidome analysis are expected to contribute to the improvement of Koshu wine aroma and breeding strategies of cold-tolerant Koshu grapevines.

Effect of regulated deficit irrigation on fatty acids and their derived volatiles in 'Cabernet Sauvignon' grapes and wines of Ningxia, China

The effect of regulated deficit irrigation (RDI) on fatty acids and their derived volatiles in 'Cabernet Sauvignon' grapes and wines was investigated during two growing seasons in the east foot of Mt. Helan, the semi-arid area. The vines received water with 60% (RDI-1), 70% (RDI-2), 80% (RDI-3), 100% (CK, traditional drip irrigation) of their estimated evapotranspiration (ETc) respectively. RDI treatments resulted in lower yield, berry weight and titratable acidity with higher total soluble solids. RDI-1 increased the content of unsaturated fatty acids in berries and decreased the level of alcohols and esters volatiles in wines. RDI-2 and RDI-3 enhanced 1-hexanol and esters in wines in comparison with CK. The concentrations of C₆ aroma compounds were closely correlated with unsaturated fatty acids (p < .05), especially linolenic acid and linoleic acid. The present results provided direct evidence and detailed data to explain the effect of RDI on grapes and wines composition regarding fatty acids and their derived volatiles.

Effect of Vertical Shoot-Positioned, Scott-Henry, Geneva Double-Curtain, Arch-Cane, and Parral Training Systems on the Volatile Composition of Albariño Wines

Viticultural practices influence both grape and wine quality. The influence of training systems on volatile composition was investigated for Albariño wine from Rías Baixas AOC in Northwest Spain. The odoriferous contribution of the compounds to the wine aroma was also studied. Volatile compounds belonging to ten groups (alcohols, C₆-compounds, ethyl esters, acetates, terpenols, C₁₃-norisoprenoids, volatile phenols, volatile fatty acids, lactones and carbonyl compounds) were determined in Albariño wines from different training systems, Vertical Shoot-Positioned (VSP), Scott-Henry (SH), Geneva Double-Curtain (GDC), Arch-Cane (AC), and Parral (P) during 2010 and 2011 vintages. Wines from GDC showed the highest total volatile composition with the highest concentrations of alcohols, ethyl esters, fatty acids, and lactones families. However, the highest levels of terpenes and C₁₃-norisoprenoids were quantified in the SH system. A fruitier aroma was observed in Albariño wines from GDC when odor activity values were calculated.

Varietal Dependence of GLVs Accumulation and LOX-HPL Pathway Gene Expression in Four Vitis vinifera Wine Grapes

Variety is one of the major factors influencing grape and wine aromatic characteristics. Green leaf volatiles (GLVs), derived from lipoxygenase-hydroperoxides lyase (LOX-HPL) pathway, are important components for the aromatic quality of grapes and wines. However, the varietal difference regarding GLVs accumulation and related gene expression are poorly studied. This work exhibited that the accumulation of various GLVs and the expression of LOX-HPL pathway genes in four Vitis vinifera wine grape cultivars: Syrah, Muscat Tchervine, Gewürztraminer and Chardonnay. The results showed a variety dependence of GLVs profile. Muscat Tchervine harvested grapes contained less C6 aldehydes and the most abundant esters, which corresponded to very low VvLOXA and VvHPL1 expression abundance as well as high VvAAT transcript in this variety. High expression level of both VvLOXA and VvHPL1 paralleled with higher level of C6 aldehydes together with higher alcohols in Syrah grape. Gewürztraminer and Chardonnay grapes had high aldehydes and alcohols as well as low esters, which were resulted from their higher expression level of VvLOXA or VvHPL1 and lower VvAAT. From these above corresponding relations, it is concluded that VvLOXA, VvHPL1 and VvAAT in the LOX-HPL pathway are targets for altering GLVs composition in the grape varieties.

Effect of Exogenous Abscisic Acid and Methyl Jasmonate on Anthocyanin Composition, Fatty Acids, and Volatile Compounds of Cabernet Sauvignon (Vitis vinifera L.) Grape Berries

The anthocyanin composition, fatty acids, and volatile aromas are important for Cabernet Sauvignon grape quality. This study evaluated the effect of exogenous abscisic acid (ABA) and methyl jasmonate (MeJA) on the anthocyanin composition, fatty acids, lipoxygenase activity, and the volatile compounds of Cabernet Sauvignon grape berries. Exogenous ABA and MeJA improved the content of total anthocyanins (TAC) and individual anthocyanins. Lipoxygenase (LOX) activity also increased after treatment. Furthermore, 16 fatty acids were detected. The linoleic acid concentration gradually increased with ABA concentration. The fatty acid content decreased with increasing MeJA concentration and then increased again, with the exception of linoleic acid. After exogenous ABA and MeJA treatment, the C6 aroma content increased significantly. Interestingly, the exogenous ABA and MeJA treatments improved mainly the content of 1-hexanol, hexanal, and 2-heptanol. These results provide insight into the effect of plant hormones on wine grapes, which is useful for grape quality improvement.

Attenuated UV Radiation Alters Volatile Profile in Cabernet Sauvignon Grapes under Field Conditions

This study aimed to explore the effect of attenuated UV radiation around grape clusters on the volatile profile of Cabernet Sauvignon grapes (Vitis vinifera L. cv.) under field conditions. Grape bunches were wrapped with two types of polyester films that cut off 89% (film A) and 99% (film B) invisible sunlight of less than 380 nm wavelength, respectively. Solar UV radiation reaching the grape berry surface was largely attenuated, and an increase in the concentrations of amino acid-derived benzenoid volatiles and fatty acid-derived esters was observed in the ripening grapes. Meanwhile, the attenuated UV radiation significantly reduced the concentrations of fatty acid-derived aldehydes and alcohols and isoprenoid-derived norisoprenoids. No significant impact was observed for terpenes. In most case, these positive or negative effects were stage-dependent. Reducing UV radiation from the onset of veraison to grape harvest, compared to the other stages, caused a larger alteration in the grape volatile profile. Partial Least Square Discriminant Analysis (PLS-DA) revealed that (E)-2-hexenal, 4-methyl benzaldehyde, 2-butoxyethyl acetate, (E)-2-heptenal, styrene, α-phenylethanol, and (Z)-3-hexen-1-ol acetate were affected most significantly by the attenuated UV radiation.