Impact of agronomic practices on grape aroma composition: a review

Non-targeted analysis using gas chromatography mass spectrometry to assess the free and bound aroma fingerprints of the emblematic Greek white winegrape varieties and guarantee varietal authenticity using multivariate chemometrics

A non-targeted analytical approach using gas chromatography-mass spectrometry (GC-MS) is proposed for the analysis of the free and bound volatile fractions of three emblematic indigenous Greek white winegrape varieties belonging to Vidiano, Malagousia, and Savvatiano and establish volatile varietal markers using multivariate chemometrics. A total of 89 free and 103 bound volatile compounds were identified, categorized into alcohols, aldehydes, esters, acids, terpenes, norisoprenoids, C6 compounds, phenols, and ketones. A robust Partial Least Squares Discriminant Analysis (PLS-DA) prediction model was developed and validated, and successfully classified the grape samples according to the variety with 100 % accuracy, demonstrating the potential of volatile profiling as a non-targeted fingerprinting approach for varietal discrimination. Malagousia variety exhibited the highest concentration of terpenes, particularly in the bound fraction, highlighting its intense floral character. The proposed analytical workflow was successfully applied for the investigation of the unique aroma profiles of Greek white winegrape varieties. The findings contribute to the understanding of unique volatile fingerprints of the winegrape varieties and support the adaptation of vineyard and winery practices to enhance their varietal expression.

Manganese biofortification in grapevine by foliar spraying improves volatile profiles of Cabernet Sauvignon grapes and wine sensory traits

Manganese (Mn) is involved in plant metabolism as an enzyme cofactor. However, the role of Mn in the formation of volatile compounds in grapes has rarely been studied. To address this gap, this study explored the effect of foliar Mn application on the aroma traits of grapes and wine. Mn nutrient solutions at different concentrations (0 (CK), 300, 1200, and 2400 mg/L) were sprayed on grapevines in 2017 and 2018 and the volatile compounds, odor activity, and sensory features of grapes and wine were investigated. The results showed that Mn application significantly increased Mn content in grape leaves and fruits at harvest. Compared with CK, the total volatile content of grapes was significantly increased by Mn treatment in both years because of the promotion of the accumulation of alcohols and esters. Particularly, 1200 mg/L Mn treatment resulted in a higher sensory score than CK, especially in terms of intensity, duration, and harmony. Multivariate analysis and odor activity values jointly identified eight volatile compounds (ethyl acetate, phenylethyl acetate, and phenylethyl alcohol, etc.) as key odorants that contribute to the floral and fruity flavors of Mn-treated wine. Overall, this study indicated that a moderate concentration of Mn is beneficial for improving the fragrance characteristics of grapes and wines. The results have implications for micronutrient management of grapevines to improve wine flavor quality.

Technological affinity index for interaction between lactic acid bacteria and Saccharomyces cerevisiae strains to modulate the fruity and floreal aroma of Catarratto wines

Microbial interactions during the fermentation process influence the sensory characteristics of wines. Alongside alcoholic fermentation, malolactic fermentation also plays a crucial role in determining the aromatic traits of wines. The time (t), rate (m) and volatile organic compounds (VOCs) of malolactic fermentation are linked to the interaction between yeasts and lactic acid bacteria. The study investigated the interactions between Lactiplantibacillus plantarum or Oenococcus oeni with Saccharomyces cerevisiae by using the Technological Affinity Index (TAIndex). The co-inoculation of L. plantarum/S. cerevisiae resulted in a higher TAIndex than the co-inoculation of O. oeni/S. cerevisiae conditions. A low TAIndex led to increased aromaticity of the wines. The time and rate of malolactic fermentation have a strong impact on the synthesis of VOCs with a high olfactory impact. Therefore, knowledge of the TAIndex could play a decisive role in improving winemaking planning to produce wines with higher fruit and floral perceptions.

Aroma Identification and Traceability of the Core Sub-Producing Area in the Helan Mountain Eastern Foothills Using Two-Dimensional Gas Chromatography and Time-of-Flight Mass Spectrometry and Chemometrics

The combination of volatile compounds endows wines with unique aromatic characteristics and is closely related to their geographical origins. In the pursuit of origin identification and the subdivision of homogeneous production areas, clarifying the characteristics of production areas is of great significance for improving wine quality and commercial value. In this study, GC×GC-TOFMS technology was used to analyze the aroma characteristics of "Cabernet Sauvignon" wines from 26 wineries in the Helan (HL), Yinchuan (YC), Yongning (YN), Qingtongxia (QTX), and Hongsibu (HSP) sub-producing areas in the eastern foothills of Helan Mountain in Ningxia, China. The results indicate a gradual increase in relative humidity from the southern part of Ningxia, with the YN sub-region showing optimal fruit development and the QTX region having the highest maturity. A total of 184 volatile compounds were identified, with 36 compounds with an OAV > 1, crucial for the aroma profiles of primarily fermentation-derived alcohols and esters. An aromatic vector analysis revealed that "floral" and "fruity" notes are the primary characteristics of Cabernet Sauvignon wines from the Helan Mountain East region, with lower maturity aiding in the retention of these aromas. By constructing a reliable OPLS-DA model, it was determined that 15 substances (VIP > 1) played a crucial role in identifying production areas, among which phenylethyl alcohol and isoamyl alcohol were the main contributors. In addition, a Pearson correlation analysis showed a negative correlation between sunlight duration during the growing season and benzyl alcohol accumulation, while a significant positive correlation was observed during the ripening period. Due to the critical role of phenyl ethanol in identifying producing areas, this further demonstrates that sunshine conditions may be a key factor contributing to the differences in wine flavor across regions. This study offers a theoretical foundation for understanding the relationship between climatic factors and flavor characteristics, addressing the issue of wine homogenization in small production areas, clarifying typical style characteristics, and establishing a traceability technology system based on characteristic aroma.

Effects of foliar application of methyl jasmonate and/or urea, conventional or via nanoparticles, on grape volatile composition

BACKGROUND

Viticulture has adapted foliar applications of biostimulants as a tool to improve crop quality. Recently, nanotechnology has been incorporated as a strategy to reduce the loss of biostimulants and treat nutrient deficiencies. Therefore, the present study aimed to investigate the effect of foliar applications of amorphous calcium phosphate nanoparticles (ACP) doped with methyl jasmonate (ACP-MeJA) and urea (ACP-Ur), individually or together (ACP-MeJA+Ur), on the content of volatile compounds in 'Tempranillo' grapes, compared to the conventional application of MeJA and Ur, individually or in combination (MeJA+Ur).

RESULTS

The results showed that nanoparticle treatments reduced the total C6 compounds and some carbonyl compounds in the grape musts. This is of novel interest because their presence at high levels is undesirable to quality. In addition, some aroma-positive compounds such as nerol, neral, geranyl acetone, β-cyclocitral, β-ionone, 2-phenylethanal and 2-phenylethanol increased, despite applying MeJA and Ur at a lower dose.

CONCLUSION

Consequently, although few differences in grape volatile composition were detected, nanotechnology could be an option for improving the aromatic quality of grapes, at the same time as reducing the required doses of biostimulants and generating more sustainable agricultural practices. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of High-Hydrostatic-Pressure Treatment on Polyphenols and Volatile Aromatic Compounds in Marselan Wine

This study investigated the effects of high-hydrostatic-pressure (HHP) treatment of varying intensity (100-600 MPa) and duration (10-30 min) on polyphenols and volatile aromatic compounds in Marselan red wine. The types and concentrations of polyphenols and volatile aromatic compounds were compared before and after HHP treatment; the results indicated that HHP treatment at 300 MPa for 20 min significantly increased the total polyphenol content to 369.70 mg/L, a rise of 35.82%. The contents of key polyphenols, such as resveratrol and protocatechuic acid, were significantly enhanced. Furthermore, while the total content of volatile aromatic compounds did not change significantly under this condition compared to the untreated samples, the concentration of ester compounds significantly increased to 1.81 times that of the untreated group, thereby enriching the floral and fruity aromas of the wine and effectively improving its aromatic profile and sensory quality. Principal component analysis (PCA) further validated the positive impact of HHP treatment on the flavor characteristics of Marselan red wine. These findings provide technical support for the use of HHP in improving wine quality.

Preharvest application of MeJA enhancing the quality of postharvest grape berries via regulating terpenes biosynthesis and phenylpropanoid metabolisms

Methyl jasmonate (MeJA) is an important phytohormone that regulates the development of grape, but the effect and underpin mechanism of its preharvest application on secondary metabolites accumulation in postharvest grape berries are still unclear. In this study, the transcriptome profiles combined with metabolic components analysis were used to determine the effect of preharvest MeJA application on the quality formation of postharvest rose-flavor table grape Shine Muscat. The results indicated that preharvest MeJA treatment had no significant effect on TSS content, but had a down-regulation effect on the accumulation of reducing sugar and titratable acid in the berries. The content of chlorophylls and carotenoids in treated berries was significantly higher than that of the control. Many phenolic components, such as trans-ferulic acid, resveratrol, quercetin, and kaempferol, were sensitive to MeJA and their contents were also significantly higher than that of the control under MeJA treatments during the shelf life. Compared with other volatile aroma components, terpenoid components were more sensitive to preharvest MeJA signals, the content of which presented an overall upward trend with increasing MeJA concentration and prolonging storage time. Furthermore, most of the differentially expressed genes in the general phenylpropanoid pathway and terpenoid biosynthesis pathway were up-regulated responding to MeJA signals. The most upregulated regulatory factors, such as VvWRKY72, VvMYB24, and VvWRI1, may be involved in MeJA signal transduction and regulation. Preharvest MeJA may be an effective technique for enhancing the quality of postharvest Shine Muscat grape berries, with its positive effect on enhancing the characteristic aroma and nutritional components.

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.

Genomic analysis reveals genes that encode the synthesis of volatile compounds by a Bacillus velezensis-based biofungicide used in the treatment of grapes to control Aspergillus carbonarius

Fungal control strategies based on the use of Bacillus have emerged in agriculture as eco-friendly alternatives to replace/reduce the use of synthetic pesticides. Bacillus sp. P1 was reported as a new promising strain for control of Aspergillus carbonarius, a known producer of ochratoxin A, categorized as possible human carcinogen with high nephrotoxic potential. Grape quality can be influenced by vineyard management practices, including the use of fungal control agents. The aim of this study was to evaluate, for the first time, the quality parameters of Chardonnay grapes exposed to an antifungal Bacillus-based strategy for control of A. carbonarius, supporting findings by genomic investigations. Furthermore, genomic tools were used to confirm that the strain P1 belongs to the non-pathogenic species Bacillus velezensis and also to certify its biosafety. The genome of B. velezensis P1 harbors genes that are putatively involved in the production of volatiles and hydrolytic enzymes, which are responsible for releasing the free form of aroma compounds. In addition to promote biocontrol of phytopathogenic fungi and ochratoxins, the treatment with B. velezensis P1 did not change the texture (hardness and firmness), color and pH of the grapes. Heat map and hierarchical clustering analysis (HCA) of volatiles evaluated by GC/MS revealed that Bacillus-treated grapes showed higher levels of compounds with a pleasant odor descriptions such as 3-hydroxy-2-butanone, 2,3-butanediol, 3-methyl-1-butanol, 3,4-dihydro-β-ionone, β-ionone, dihydroactinidiolide, linalool oxide, and β-terpineol. The results of this study indicate that B. velezensis P1 presents desirable properties to be used as a biocontrol agent.

Recent Advances and Future Perspectives in the E-Nose Technologies Addressed to the Wine Industry

Electronic nose devices stand out as pioneering innovations in contemporary technological research, addressing the arduous challenge of replicating the complex sense of smell found in humans. Currently, sensor instruments find application in a variety of fields, including environmental, (bio)medical, food, pharmaceutical, and materials production. Particularly the latter, has seen a significant increase in the adoption of technological tools to assess food quality, gradually supplanting human panelists and thus reshaping the entire quality control paradigm in the sector. This process is happening even more rapidly in the world of wine, where olfactory sensory analysis has always played a central role in attributing certain qualities to a wine. In this review, conducted using sources such as PubMed, Science Direct, and Web of Science, we examined papers published between January 2015 and January 2024. The aim was to explore prevailing trends in the use of human panels and sensory tools (such as the E-nose) in the wine industry. The focus was on the evaluation of wine quality attributes by paying specific attention to geographical origin, sensory defects, and monitoring of production trends. Analyzed results show that the application of E-nose-type sensors performs satisfactorily in that trajectory. Nevertheless, the integration of this type of analysis with more classical methods, such as the trained sensory panel test and with the application of destructive instrument volatile compound (VOC) detection (e.g., gas chromatography), still seems necessary to better explore and investigate the aromatic characteristics of wines.

Targeted metabolomics analysis based on HS-SPME-GC-MS to discriminate geographical origin of 'Muscat Hamburg' grape and wine

Monoterpenes are typical aroma components in muscat grapes and wines, closely related to its geographical origins. However, the mechanism underlying the geographical differences of monoterpenes remains to be elucidated, especially in the Chinese viticulture regions. This study investigated the diversity of six Chinese viticultural vineyards (YT, XF, SS, XX, WW and CL) in the monoterpene composition of Vitis vinifera L. cv.'Muscat Hamburg' grapes and the resulted wines. Monoterpenes were analyzed by HS-SPME- GC-MS. The total amount of free and bound monoterpenes varied dramatically between grapes of different vineyards, and their contents were obviously higher in YT region grapes. The OAVs for 18 monoterpenes of grapes from the YT vineyard were relative higher than those of other regions, and the floral odor could distinguish grapes from different regions. The total free monoterpenes were highest in the YT region wine. Concentrations of total bound monoterpenes ranged from 711.13 μg/L (XF region) to 1078.30 μg/L (CL region). A correlation analysis showed that all monoterpenes showeda positive correlation with mean relative humidity, sum rainfall, and a negative correlation with sum duration of sunshine and mean temperature. This study would provide some new insights to understand the geographical differences of monoterpenes, and the results would facilitate the effective viticultural treatment of grapes to improve the quality of the aroma.

Evolution of Leaf Chlorophylls, Carotenoids and Phenolic Compounds during Vegetation of Some Croatian Indigenous Red and White Grape Cultivars

During the ripening process of grapes, the grapevine leaves are the most active green organs that are important for photosynthesis, which is closely linked to the development and metabolism of the plant. The detection of plant pigments and phenolic compounds in grapevine leaves can be a good indicator of the ageing process, vine vigor and the plant's ability to respond to fungal attack. In a one-year study, the development of leaf chlorophylls, carotenoids and phenolic compounds during the ripening of six indigenous Croatian grape cultivars and the international cultivars Merlot and Chardonnay was investigated. The chlorophyll a/b ratio and total chlorophyll and total carotenoid concentrations were also investigated. PCA was used to highlight relevant information from the data with the aim of distinguishing individual compounds based on the cultivar and phenological stage. The leaf total hydroxycinnamic acid and flavan-3-ol concentrations decreased slowly during grape development, with the highest concentration immediately after flowering and the lowest during grape ripening. The concentrations of β-carotene, lutein and xanthophylls tended to decrease during bunch closure or veraison, while the concentration of chlorophylls a and b peaked during veraison and then decreased during grape ripening. This research will provide an opportunity to select cultivars with the physiological adaptation to synthesize secondary metabolites that are important for managing stress conditions.

New Fungus-Resistant Grapevine Vitis and V. vinifera L. × M. rotundifolia Derivative Hybrids Display a Drought-Independent Response in Thiol Precursor Levels

The use of new disease-resistant grapevine varieties is a long-term but promising solution to reduce chemical inputs in viticulture. However, little is known about water deficit effects on these varieties, notably regarding berry composition. The aim of this study was to characterize the primary metabolites and thiol precursors levels of 6 fungi-resistant varieties and Syrah. Vines were grown under field conditions and under different water supply levels, and harvested at the phloem unloading arrest. A great variability among varieties regarding the levels of thiol precursors was observed, with the highest concentration, of 539 μg/kg, being observed in 3176-N, a hybrid displaying red fruits. Water deficit negatively and equally impacted the accumulation of sugars, organic acids, and thiol precursors per berry and per plant, with minor effects on their concentration. The observed losses of metabolites per cultivation area suggest that water deficits can lead to significant economic losses for the producer.

Nanoparticles doped with methyl jasmonate: foliar application to Monastrell vines under two watering regimes. An alternative to improve grape volatile composition?

BACKGROUND

Elicitors induce defense mechanisms, triggering the synthesis of secondary metabolites. Irrigation has implications for a more sustainable viticulture and for grape composition. The aim was to investigate the influence on grape aroma composition during 2019 and 2020 of the foliar application of amorphous calcium phosphate (ACP) nanoparticles and ACP doped with methyl jasmonate (ACP-MeJ), as an elicitor, with rainfed or regulated deficit irrigation (RDI) grapevines.

RESULTS

In both growing seasons, nearly all terpenoids, C13 norisoprenoids, benzenoid compounds and alcohols increased with ACP-MeJ under the RDI regimen. In 2019, under the rainfed regime, ACP treatment increased limonene, p-cymene, α-terpineol, 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), 2-ethyl-1-hexanol, (E,E)-2,4-heptadienal, and MeJ concentration in comparison with control grapes. In 2020, the rainfed regime treated with ACP-MeJ only increased the nonanoic acid content. Grape volatile compounds were most influenced by season and watering status whereas the foliar application mainly affected the terpenoids.

CONCLUSION

A RDI regime combined with the elicitor ACP-MeJ application could improve the synthesis of certain important volatile compounds, such as p-cymene, linalool, α-terpineol, geranyl acetone, β-ionone, 2-phenylethanol, benzyl alcohol, and nonanoic acid in Monastrell grapes. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Metabolomic and transcriptomic integrated analysis revealed the decrease of monoterpenes accumulation in table grapes during long time low temperature storage

Low temperature is the commonly used technique for maintaining the quality of table grapes during postharvest storage. However, this technique could strongly affect the aromatic flavor of fruit. Monoterpenes are the key compounds contributing to the Muscat aromas of grapes. The detailed information and molecular mechanisms underlying the changes in monoterpenes during postharvest low temperature storage have not been thoroughly characterized. In this study, the effects of low temperature storage on the free and bound monoterpene profiles in four cultivars of table grape were determined at both the transcriptomic and metabolomic levels. A total of 27 compounds in both free and bound forms were identified in the four cultivars and showed quantitative differences between the cultivars. Hierarchical cluster and principal component analysis indicated that the free and bound monoterpene profiles were remarkably affected by the low temperature storage. The monoterpenes in the same biosynthesis pathway were clustered together and showed similar evolution trends during low temperature storage. And the content of most of free monoterpenes underwent a rapid decline during low-temperature storage at a certain stage, but the time was different in 4 grape cultivars. Transcriptomic analysis revealed that the expression of DXS, HDR, GPPS and TPS genes involved in the monoterpene synthesis pathway were consistent with the changes in the accumulation of monoterpene compounds. While the expression of HMGS, HMGR genes in MVA pathway and branch genes GGPPS and FPPS were negatively correlated with the accumulation of monoterpenes. The findings provide new insights into the underlying mechanisms of the berry aroma flavor change during low temperature storage.

Impact of Climate Change on Altered Fruit Quality with Organoleptic, Health Benefit, and Nutritional Attributes

As a consequence of global climate change, acute water deficit conditions, soil salinity, and high temperature have been on the rise in their magnitude and frequency, which have been found to impact plant growth and development negatively. However, recent evidence suggests that many fruit plants that face moderate abiotic stresses can result in beneficial effects on the postharvest storage characters of the fruits. Salinity, drought, and high temperature conditions stimulate the synthesis of abscisic acid (ABA), and secondary metabolites, which are vital for fruit quality. The secondary metabolites like phenolic acids and anthocyanins that accumulate under abiotic stress conditions have antioxidant activity, and therefore, such fruits have health benefits too. It has been noticed that fruits accumulate more sugar and anthocyanins owing to upregulation of phenylpropanoid pathway enzymes. The novel information that has been generated thus far indicates that the growth environment during fruit development influences the quality components of the fruits. But the quality depends on the trade-offs between productivity, plant defense, and the frequency, duration, and intensity of stress. In this review, we capture the current knowledge of the irrigation practices for optimizing fruit production in arid and semiarid regions and enhancement in the quality of fruit with the application of exogenous ABA and identify gaps that exist in our understanding of fruit quality under abiotic stress conditions.

Main flavor compounds and molecular regulation mechanisms in fruits and vegetables

Fruits and vegetables (F&V) are an indispensable part of a healthy diet. The volatile and nonvolatile compounds present in F&V constitute unique flavor substances. This paper reviews the main flavor substances present in F&V, as well as the biosynthetic pathways and molecular regulation mechanisms of these compounds. A series of compounds introduced include aromatic substances, soluble sugars and organic acids, which constitute the key flavor substances of F&V. Esters, phenols, alcohols, amino acids and terpenes are the main volatile aromatic substances, and nonvolatile substances are represented by amino acids, fatty acids and carbohydrates; The combination of these ingredients is the cause of the sour, sweet, bitter, astringent and spicy taste of these foods. This provides a theoretical basis for the study of the interaction between volatile and nonvolatile substances in F&V, and also provides a research direction for the healthy development of food in the future.

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.

Effects of Leaf Removal on Free and Glycoconjugate Aromas of Skins and Pulps of Two Italian Red Grapevine Varieties

Leaf removal is a cultural practice mainly aimed at improving cluster zone microclimates and impacting primary and secondary metabolites, such as volatiles. This research aimed to assess the impact of defoliation on free and glycosylated aromas of a neutral ('Nebbiolo') and a semi-aromatic ('Aleatico') red variety. Defoliation was performed at fruit set (BBCH 71) and, for 'Nebbiolo', also at berries touch (BBCH 81) phenological stages. Skins and pulps were separately analyzed by Solid Phase Extraction-Gas Chromatography/Mass Spectrometry. Results showed that the response to defoliation was variety-dependent. For 'Nebbiolo', especially when performed at the berries' touch stage, defoliation had a significant effect on the accumulation of free volatiles and glycosidic precursors. Differently, free and bound 'Aleatico' volatiles were less impacted by defoliation. Interestingly, in both grapevine varieties, defoliation significantly enhanced the accumulation of aroma precursors in grapes' skins, which is of particular relevance for red wine production and their aging potential. Moreover, results could be helpful for the management of grape quality, as defoliation is currently considered as a strategy to address climate change issues.

Application of near-infrared spectroscopy for the estimation of volatile compounds in Tempranillo Blanco grape berries during ripening

BACKGROUND

The knowledge of volatile compounds concentration in grape berries is very valuable information for the winemaker, since these compounds are strongly involved in the final wine quality, and in consumer acceptance. In addition, it would allow to set the harvest date according to aromatic maturity, to classify grape berries according to their quality and to make wines with different characteristics, among other implications. However, so far, there are no tools that allow the volatile composition to be measured directly on intact berries, either in the vineyard or in the winery.

RESULTS

In this work, the use of near-infrared (NIR) spectroscopy to estimate the aromatic composition and total soluble solids (TSS) of Tempranillo Blanco grape berries during ripening was evaluated. For this purpose, the spectra in the NIR range (1100-2100 nm) of 240 intact berry samples were acquired in the laboratory. From these same samples, the concentration of volatile compounds was analyzed by thin film-solid-phase microextraction-gas chromatography-mass spectrometry (TF-SPME-GC-MS), and the TSS were quantified by refractometry. These two methods were used as reference methods for model building. Calibration, cross-validation and prediction models were built from spectral data using partial least squares (PLS). Determination coefficients of cross-validation (R2 CV ) above 0.5 were obtained for all volatile compounds, their families, and TSS.

CONCLUSIONS

These findings support that NIR spectroscopy can be successfully use to estimate the aromatic composition as well as the TSS of intact Tempranillo Blanco berries in a non-destructive, fast, and contactless form, allowing simultaneous determination of technological and aromatic maturities. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Table Grape Cultivars on Fruit Quality and Aroma Components

The basic physical and chemical qualities, nutrition, aroma components, and sensory evaluation of 17 varieties of table grapes were studied. The quality evaluation system of different table grape varieties was preliminarily determined. Our results show that the soluble solid content in Ruby Seedless was 21.17%, which was higher than that of other varieties. The black varieties Aishenmeigui and Sweet Sapphire had the highest total phenol content. Aishenmeigui had high levels of tannin and vitamin C. In addition, the aroma contents in Meixiangbao, Ruby Seedless, and Shine-Muscat were higher than those in other varieties. Manicure Finger and Ruby Seedless had higher levels of C6 compounds. Moreover, the "Kyoho" series of grape Meixiangbao, Sunmmer Black, Jumeigui, Hutai 8 hao, and Black Beet were high in ester content, while Muscat varieties, including Zaoheibao, Aishenmeigui, Jumeigui, and Shine-Muscat were rich in terpene substances. Ruby Seedless, Shine-Muscat, and Heibaladuo had higher comprehensive scores in sensory evaluation. Hence, the comprehensive quality of Shine-Muscat, Ruby Seedless, and Aishenmeigui was better. These results may serve as references for determining the quality differences between table grape varieties.

Could foliar applications of methyl jasmonate and methyl jasmonate + urea improve must grape aroma composition?

BACKGROUND

Grape aromas are formed by a great number of volatile compounds. Methyl jasmonate (MeJ) and urea (Ur) foliar applications have been studied to improve grape quality, but their combined application has never been studied.

RESULTS

In both seasons, MeJ application enhanced terpenoids and C6 compounds synthesis, though decreased alcohols content. Moreover, MeJ + Ur treatment reduced benzenoids and alcohols and did not affect C₁₃ -norisoprenoids content. However, there was no clear effect of these treatments on the rest of the volatile compounds. Multifactorial analysis showed a season effect on all volatile compounds, except terpenoids. Discriminant analysis showed a good separation among samples under treatment criterion. The great effect of MeJ treatment on terpenoids was probably due to this elicitor influencing their biosynthesis.

CONCLUSION

Season has a strong influence on grapes aromatic composition since it affects all volatile compound families except terpenoids. MeJ foliar application enhanced terpenoids, C₁₃ -norisoprenoids and C6 compounds synthesis, whereas decreased alcohols content; however, MeJ + Ur foliar treatment did not affect C₁₃ -norisoprenoids and C6 compounds, and decreased benzenoids and alcohols grape compounds. Therefore, no synergistic effect was observed between Ur and MeJ on grape volatile compounds biosynthesis. Foliar application of MeJ seems to be sufficient to improve the aromatic quality of grapes. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Aroma precursors of Grignolino grapes (Vitis vinifera L.) and their modulation by vintage in a climate change scenario

Current climatic conditions may cause significant changes in grapevine phenology and maturity dynamics linked often with changes to ecoclimatic indicators. The influence exerted by different meteorological conditions during four consecutive years on the aromatic potential of Grignolino grapes was investigated for the first time. The samples were collected from three vineyards characterized by different microclimatic conditions mainly related to the vineyard exposure and by a different age of the plants. Important differences as far as temperature and rainfall patterns are concerned during ripening were observed among the 4 years. Grape responses to abiotic stress, with particular emphasis on aromatic precursors, were evaluated using gas chromatography coupled to mass spectrometry. The results highlighted significant differences among the vintages for each vineyard in terms of the berry weight and the aromatic precursor concentration. For the grapes of the younger-vine vineyard, the content of aroma compounds showed a different variability among the vintages if compared to the old-vine vineyards. Optimal conditions in terms of temperature and rainfall during the green phase followed by a warm and dry post-veraison period until harvest favored all classes of compounds especially terpenoids mainly in the grapes of the old vines. High-temperature (>30°C) and low-rainfall pattern before veraison led to high benzenoid contents and increased differences among vineyards such as berry weight, whereas cooler conditions favored the terpenoid levels in grapes from southeast-oriented vineyards. In a hilly environment, lack of rainfall and high temperature that lately characterize the second part of berry development seem to favor the grape quality of Grignolino, a cultivar of medium-late ripening, by limiting the differences on bunch ripening, allowing a greater accumulation of secondary metabolites but maintaining at the same time an optimum balance sugar/acidity.

Effects of Inner-Row Ground Management on the Volatomics of 'Cabernet Sauvignon' Grapes and Wines in the Region of the Eastern Foothills of the Ningxia Helan Mountains in Northwest China

This two-consecutive-year study aimed to evaluate the effects of ground management methods on the volatomics of 'Cabernet Sauvignon' grapes and wines in Northwest China, in which inner-row crop covering with purslane (GRASS) and mulching with black plastic film (FILM) treatments were carried out, respectively. Compared with clean tillage (CK), the GRASS and FILM treatments changed the microclimates of grapevine fruit zones and rhizospheres, which delayed the ripening of grape berries and affected the accumulation of aroma substances in the mature grapes effectively. GRASS increased the concentration of terpenes and C₁₃-norisoprenoids in berries and gave more floral, fruity, and caramel fragrances to wines, while FILM had the opposite effect of significantly increasing the synthesis of C₆/C₉ compounds and brought more green leaf flavors, showing that inner-row purslane covering is a potential and stable viticultural practice to improve the wine quality in this booming wine region.

Effects of ultraviolet and infrared radiation absence or presence on the aroma volatile compounds in winegrape during veraison

Light environmental factors have been identified to influence grape aromas greatly. Among them, the effect of non-visible light on grape aroma compounds has scarcely been investigated during grape growth and development. In the present study, ultraviolet (UV) or infrared (IR) radiation was eliminated in the grape bunch zone, and the grape bunches were irradiated with UV or IR light in vitro. The effect of UV and IR radiation on the grape aroma profile of the Cabernet Sauvignon variety was assessed by headspace solid phase microextraction gas chromatography mass spectrometer (HS-SPME GC-MS). A total of 16 aroma compounds were identified in the grape berries under UV radiation absence (UV-) or IR radiation absence (IR-). They were classified into aliphatic alcohols, aliphatic acids, benzenolds, aldehydes, and monoterpenes. A total of 23 aroma compounds were identified in the grape berries under UV radiation presence (UV+) or IR radiation presence (IR+), which were classified into aliphatic alcohols, aliphatic ketones, aliphatic esters, aliphatic acids, monoterpenes, aldehydes, volatile phenols, and other volatiles. Linalool and hexanal aroma compounds were the most responsive to UV- and UV+, according to OPLS-DA analysis. Hexanal was increased by UV- and decreased by UV+, thus was negatively correlated with UV radiation. Benzaldehyde and 2-decanone were also found as the main differing aroma compounds according to VIP scores in the IR- and IR+, respectively. The significant differences of aroma compounds in three UV and IR intensities were also observed by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The content of acetic acid, 2-methylbutanal, and pentanal were reduced with the radiation intensity increase, and the content of 2-3-butanedione, butyl acetate, and 1-hexanol was enhanced, especially with UV radiation. This study improves our understanding of the non-visible light role in volatile aroma compound accumulation and further expands on the useful wavelength for plant growth and development. Our study provides a theoretical basis for non-visible light field management and indoor plant growth applications.

Monitorization of Varietal Aroma Composition Dynamics during Ripening in Intact Vitis vinifera L. Tempranillo Blanco Berries by Hyperspectral Imaging

The measurement of aromatic maturity during grape ripening provides very important information for determining the harvest date, particularly in white cultivars. However, there are currently no tools that allow this measurement to be carried out in a noninvasive and rapid way. For this reason, in the present work, we have studied the use of hyperspectral imaging (HSI)) to estimate the aromatic composition of Vitis vinifera L. Tempranillo Blanco berries during ripening. A total of 236 spectra in the VIS+short wave near-infrared (VIS+SW-NIR) range (400-1000 nm) of intact berries were acquired contactless under laboratory conditions. As gold standard values, a total of 20 volatile compounds were quantified by gas chromatography-mass spectrometry (GC-MS), and the concentration of total soluble solids (TSS) was measured by refractometry. Calibration, cross-validation, and prediction models were built using partial least squares (PLS). Values of R_CV² ≥ 0.70 were obtained for α-terpineol, p-cymene, β-damascenone, β-ionone, benzaldehyde, benzyl alcohol, hexanal, citral, linalool, 2-phenylethanol, octanoic acid, nonanoic acid, 2-hexenal, 2-hexen-1-ol, (Z)-3-hexen-1-ol, total C₁₃ norisoprenoids, total C6 compounds, total positive compounds (i.e., the sum of all families except C6 compounds), total benzenoids, and total soluble solids (TSS). Therefore, it can be affirmed that HSI in the VIS + SW-NIR range could be a good tool to estimate the aromatic composition of Tempranillo Blanco grape berries in a contactless, fast, and nondestructive way.

Grapevine mono- and sesquiterpenes: Genetics, metabolism, and ecophysiology

Mono- and sesquiterpenes are volatile organic compounds which play crucial roles in human perception of table grape and wine flavour and aroma, and as such their biosynthesis has received significant attention. Here, the biosynthesis of mono- and sesquiterpenes in grapevine is reviewed, with a specific focus on the metabolic pathways which lead to formation of these compounds, and the characterised genetic variation underlying modulation of this metabolism. The bottlenecks for terpene precursor formation in the cytosol and plastid are understood to be the HMG-CoA reductase (HMGR) and 1-deoxy-D-xylylose-5-phosphate synthase (DXS) enzymes, respectively, and lead to the formation of prenyldiphosphate precursors. The functional plasticity of the terpene synthase enzymes which act on the prenyldiphosphate precursors allows for the massive variation in observed terpene product accumulation. This diversity is further enhanced in grapevine by significant duplication of genes coding for structurally diverse terpene synthases. Relatively minor nucleotide variations are sufficient to influence both product and substrate specificity of terpene synthase genes, with these variations impacting cultivar-specific aroma profiles. While the importance of these compounds in terms of grape quality is well documented, they also play several interesting roles in the grapevine's ecophysiological interaction with its environment. Mono- and sesquiterpenes are involved in attraction of pollinators, agents of seed dispersal and herbivores, defence against fungal infection, promotion of mutualistic rhizobacteria interaction, and are elevated in conditions of high light radiation. The ever-increasing grapevine genome sequence data will potentially allow for future breeders and biotechnologists to tailor the aroma profiles of novel grapevine cultivars through exploitation of the significant genetic variation observed in terpene synthase genes.

Characterization of wine volatile compounds from different regions and varieties by HS-SPME/GC-MS coupled with chemometrics

HS-SPME/GC-MS and aroma descriptive analysis were used to gain insights into the volatile and sensory details of 99 red wine samples collected from four varieties in five regions. The general volatile fingerprints of Cabernet Sauvignon and Merlot wine samples in Xinjiang and Ningxia regions were similar, even though chemometric models could not discriminate between them. The main drivers of the diversity were secondary metabolites of grape such as terpenes, benzene-derivatives, and ketones. Fermentation-derivatives (esters and alcohols) were also responsible for region and variety-related differences in wines. Analysis of volatile compounds also showed that the primary factor accounting for diversity in wines in this study was region rather than variety. These results highlight the sensory attributes and volatiles of different regions and varieties, and provide a quantitative basis for screening for differential metabolites and potential markers in wines.

Effect of over crop and reduced yield by cluster thinning on phenolic and volatile compounds of grapes and wines of 'Sangiovese' trained to Tendone

BACKGROUND

'Sangiovese' (Vitis vinifera L.) is a well-known Italian wine grape utilized for producing the prestigious Chianti Classico brand. Here, 'Sangiovese' is generally trained to a vertical training system, with an imposed crop level of around 3-5 kg per vine to preserve grape quality. Tendone comprises a horizontal trellis system, largely diffused in Mediterranean Countries for table grape production, and is adopted to achieve a high yield and to preserve grapes, by means of its canopy architecture, from excessive solar radiation, which in turn affects the organoleptic aspects of grapes and wines. The present study aimed to evaluate, in terms of phenolic and volatile compounds of grape and wines, 'Sangiovese' trained to Tendone, as affected by two crop levels, namely very high and reduced yields.

RESULTS

Reduced yield (18.39 kg per vine) by cluster thinning still appeared to provide a considerable yield and quality of grapes and wines. Thinning increased pH, tartaric acid content, flavonoids, anthocyanins, total polyphenols and proanthocyanins, and total free and bound aroma compounds, without affecting soluble solids and titratable acidity of grapes. As regards wines, reduced yield increased pH, tartaric and malic acids and dry reduced extract, flavonoids, anthocyanins, total polyphenols and proanthocyanins, and, finally, the color intensity of wines.

CONCLUSION

The present study highlights that Tendone training systems, combined with 40% of cluster thinning, allows a high yield to be reached, allowing, at the same time, a very interesting quality of grapes, making it possible to produce qualitative wines. © 2022 Society of Chemical Industry.

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.

The Expression of Aroma Components and Related Genes in Merlot and Marselan Scion-Rootstock Grape and Wine

Rootstocks were bred and selected from several species in order to enhance the resistance against biotic or abiotic stresses. There are few studies on the effect of rootstocks on aroma and related gene expression. This study focused on the effects of three rootstocks, Kober 5BB (5BB), 1103 Paulsen (1103P), and Selection Oppenheim (SO4), on the aroma and volatile-related gene expression levels of Merlot and Marselan berries and wines. These three rootstocks reduced the total aroma content of Merlot wine. 5BB upregulated VvLoXA and showed increased C6 alcohols. 1103P enhanced the linalool from Merlot berry, with marked upregulation of VvLinNer1. Conversely, rootstocks increased the total aroma content of Marselan berry, verified by the related expression levels of volatile-related genes. For Marselan berry, 5BB and 1103P upregulated five VvGTs and nine genes from the LOX and MEP pathway. 1103P increased the contents of C6 alcohols, C6 aldehydes, and citronellol from Marselan berry. Compared to 5BB and SO4, rootstock 1103P provided berries of better quality and richer aroma volatiles to Merlot and Marselan, while all three of the rootstocks had a significant effect on scion–rootstocks.

Influence on grape aromatic compounds of natural fungicides used for the control of downy mildew

BACKGROUND

The grape volatile fraction determines to a great extent its aroma, which is one of the most important characteristics influencing wine quality and consumer preferences. Grapevine downy mildew (GDM) is one of the most important and devastating diseases of grapevines worldwide. In this study, the impact on the volatile composition of cv. Verdicchio grapes of classical copper formulations, was compared to that of alternative products. Thus, 11 treatments were foliar applied throughout one grapevine cycle.

RESULTS

Most of the volatile compounds present in the grapes were not affected by the treatments used in order to prevent GDM. In the case of the total C₁₃ norisoprenoids, some differences were found between grapes untreated control and those applied with the grapefruit seed extract. Moreover, the content of alcohols was smaller in grapes from Bordeaux mixture treatment and higher in the samples from chitosan application.

CONCLUSION

Therefore, from the qualitative point of view of the berry, treatment with tested products alternative to copper is recommended, which minimize the environmental and health problems that this heavy metal brings to the soil and in the winery, since it means that their applications did not affect the grape aroma. © 2022 Society of Chemical Industry.

Expression Analyses in the Rachis Hint towards Major Cell Wall Modifications in Grape Clusters Showing Berry Shrivel Symptoms

Berry shrivel (BS) is one of the prominent and still unresolved ripening physiological disorders in grapevine. The causes of BS are unclear, and previous studies focused on the berry metabolism or histological studies, including cell viability staining in the rachis and berries of BS clusters. Herein, we studied the transcriptional modulation induced by BS in the rachis of pre-symptomatic and symptomatic clusters with a custom-made microarray qPCR in relation to a previous RNASeq study of BS berries. Gene set analysis of transcript expression in symptomatic rachis tissue determined suppression of cell wall biosynthesis, which could also be confirmed already in pre-symptomatic BS rachis by CESA8 qPCR analyses, while in BS berries, a high number of SWITCH genes were suppressed at veraison. Additionally, genes associated with the cell wall were differently affected by BS in berries. A high percentage of hydrolytic enzymes were induced in BS grapes in rachis and berries, while other groups such as, e.g., xyloglucan endotransglucosylase/hydrolase, were suppressed in BS rachis. In conclusion, we propose that modulated cell wall biosynthesis and cell wall assembly in pre-symptomatic BS rachis have potential consequences for cell wall strength and lead to a forced degradation of cell walls in symptomatic grape clusters. The similarity to sugar starvation transcriptional profiles provides a link to BS berries, which are low in sugar accumulation. However, further studies remain necessary to investigate the temporal and spatial coordination in both tissues.

Biochemical Traits, 1H NMR Profile and Residual DNA Content of ‘Asprinio’, White Wine from Campania Region (Southern Italy)

‘Asprinio’ is a white dry wine characteristic for its acidity and aromatic flavour, known as emerging DOP wine in Southern Italy. Nevertheless, little information is available on the metabolomic profile of this wine. Thus, in this paper we evaluated the colourimetric parameters, ¹H NMR profiles and free amino acids content of ‘Asprinio’ wines, bottled by two different wineries (hereafter ‘Asprinio_A’ and ‘Asprinio_B’) collected in 2019 and 2020, using ‘Greco di Tufo’ for comparison. The colourimetric parameters are similar for both ‘Asprinio’ wines and differ from ‘Greco di Tufo’ wines. On the other hand, both ¹H NMR and free amino acid content profiles show different chemometric profiles among the three wines analysed, although the profiles are similar for both vintages. Moreover, the multivariate analyses carried out highlight differences between ‘Asprinio_A’ and ‘Asprinio_B’, which exbibit also different residual yeast and plant DNA. Overall, considering that the two-manufacturing wineries use 100% ‘Asprinio’ grape, the difference retrieved between the two ‘Asprinio’ wines could be explained by the different grapevine training systems: ‘vite maritata’ (training system inherited from Etruscans) for ‘Asprinio_A’ and ‘guyot’ for ‘Asprinio_B’.

Volatile Compounds Analysis and Biomarkers Identification of Four Native Apricot (Prunus armeniaca L.) Cultivars Grown in Xinjiang Region of China

Flavor (odor and taste) have a significant role in the consumer’s acceptance, and volatile compounds are responsible for the odor of apricots. In the present work, headspace solid-phase microextraction with gas chromatography coupled to tandem mass spectrometry (HS-SPME-GC-MS/MS) together with multivariate analysis, i.e., partial least square discrimination analysis (PLS-DA), were applied to construct the volatile fingerprints and biomarkers of apricots in Xinjiang, China. As a result, a total of 63 volatile substances were identified in the fruits of four apricot cultivars, seven of which were considered to serve as volatile biomarkers, which are damascenone for Dabaiyou apricots; acetophenone, myrcenol and 7-hexadecenal for Luopuhongdaike apricots; 2,4-dimethyl-cyclohexanol for You apricots; eucalyptol and salicylaldehyde for Xiaobai apricots. Moreover, Xiaobai apricots were richer in soluble sugars, organic acids and total phenolic and total flavonoid content than the other three apricot varieties. This work helps to characterize the volatile profiles and biomarkers of different apricot cultivars while providing theoretical guidance for developing apricot-flavored foods in practical production.

A Comparative Analysis of Microbe-Based Technologies Developed at ICAR-NBAIM Against Erysiphe necator Causing Powdery Mildew Disease in Grapes (Vitis vinifera L.)

Globally, Erysiphe necator causing powdery mildew disease in grapevines (Vitis vinifera L.) is the second most important endemic disease, causing huge economic losses every year. At present, the management of powdery mildew in grapes is largely dependent upon the use of chemical fungicides. Grapes are being considered as one of the high pesticide-demanding crops. Looking at the residual impact of toxic chemical pesticides on the environment, animal, and human health, microbe-based strategies for control of powdery mildew is an emerging technique. It offers an environment-friendly, residue-free, and effective yet safer approach to control powdery mildew disease in grapes. The mode of action is relatively diverse as well as specific to different pathosystems. Hence, the aim of this study was to evaluate the microbe-based technologies, i.e., Eco-pesticide^®, Bio-Pulse^®, and Bio-Care 24^® developed at the Plant-Microbe Interaction and Rhizosphere Biology Lab, ICAR-NBAIM, Kushmaur, against grape powdery mildew and to integrate these technologies with a safer fungicide (sulfur) to achieve better disease control under organic systems of viticulture. The experiments were conducted at four different locations, namely, the vineyards of ICAR-NRCG, Rajya Draksha Bagayatdar Sangh (MRDBS), and two farmers' fields at Narayangaon and Junnar in the Pune district of Maharashtra. A significantly lower percent disease index (PDI) was recorded on the leaves of grape plants treated with Eco-Pesticide^®/sulfur (22.37) followed by Bio-Pulse^®/sulfur (22.62) and Bio-Care 24^®/sulfur (24.62) at NRCG. A similar trend was observed with the lowest PDI on bunches of Eco-pesticide^® /sulfur-treated plants (24.71) followed by Bio-Pulse^®/sulfur (24.94) and Bio-Care^®/sulfur (26.77). The application of microbial inoculants singly or in combination with sulfur has a significant positive impact on the qualitative parameters such as pH, total soluble solids (TSS), acidity, berry diameter, and berry length of the grapes at different locations. Among all the treatments, the Bio-Pulse^®/sulfur treatment showed the highest yield per vine (15.02 kg), which was on par with the treatment Eco-Pesticide^®/sulfur (14.94). When compared with the yield obtained from the untreated control, 2.5 to 3 times more yield was recorded in the plants treated with either of the biopesticides used in combination with sulfur. Even in the case of individual inoculation, the yield per vine was approximately two times higher than the untreated control and water-treated plants across the test locations. Results suggested that microbial technologies not only protect grapevines from powdery mildew but also enhance the quality parameters with increased yield across the test locations.

Evolution of Volatile Aroma Compounds and Amino Acids in Cabernet Gernischt Grape Berries (Vitis vinifera L.): Comparison of Different Training Systems for Mechanical Soil Burial

Soil burial is a survival strategy for grapevines that can safely overwinter in north-western regions of China. A suitable training system was beneficial for soil burial to provide winter protection. Moreover, the training system can also significantly affect fruit quality during the development of grape berries, such as primary and secondary metabolites. In this study, four-year-old Cabernet Gernischt grapevines were used as experimental material and exposed to four training systems, including the Ningxia traditional vertical trunk (control, CK); the gobelet (T1); single guyot (T2); slant trunk with vertical shoot positioning (STVSP) (T3). The results showed that total soluble solid total phenol content was 12.69%, 57% higher under T3 training systems than in the control, and T3 alleviated the canopy density, leading to improving the leaf photosynthetic efficiency gas chromatography-mass spectrometry (GC-MS) assay used to detect the aroma compounds. The results indicated that the T3 training system enhanced the accumulation of alcohols, carbonyl compounds, C6/C9 and esters, which account for the largest proportion of volatile compounds, and the qRT-PCR reveals that VvEcar, Vvter, VvCCD1, and VvLis were raised under T3 at the transcriptional level. Moreover, T3 contributes to most free amino acid synthesis. Additionally, the PCA reveals the correlation of free amino acids under four training systems, which reflected the mostly amino acid related to T3, and thus, we could speculate that T3 enhances the overall aroma. These results may lead to new strategies to select a new, short trunk training system to achieve mechanized buried soil, to prevent cold and produce high-quality wine in this area.

Application of Elicitors in Grapevine Defense: Impact on Volatile Compounds

Elicitors as alternatives to agrochemicals are widely used as a sustainable farming practice. The use of elicitors in viticulture to control disease and improve phenolic compounds is widely recognized in this field. Concurrently, they also affect other secondary metabolites, such as aroma compounds. Grape and wine aroma compounds are an important quality factor that reflects nutritional information and influences consumer preference. However, the effects of elicitors on aroma compounds are diverse, as different grape varieties respond differently to treatments. Among the numerous commercialized elicitors, some have proven very effective in improving the quality of grapes and the resulting wines. This review summarizes some of the elicitors commonly used in grapevines for protection against biotic and abiotic stresses and their impact on the quality of volatile compounds. The work is intended to serve as a reference for growers for the sustainable development of high-quality grapes.

Effects of Methyl Jasmonate and Nano-Methyl Jasmonate Treatments on Monastrell Wine Volatile Composition

The application of methyl jasmonate (MeJ) as an elicitor to enhance secondary metabolites in grapes and wines has been studied, but there is little information about its use in conjunction with nanotechnology and no information about its effects on wine volatile compounds. This led us to study the impact of nanoparticles doped with MeJ (Nano-MeJ, 1mM MeJ) on the volatile composition of Monastrell wines over three seasons, compared with the application of MeJ in a conventional way (10 mM MeJ). The results showed how both treatments enhanced fruity esters in wines regardless of the vintage year, although the increase was more evident when grapes were less ripe. These treatments also achieved these results in 2019 in the cases of 1-propanol, ß-phenyl-ethanol, and methionol, in 2020 in the cases of hexanol and methionol, and in 2021, but only in the case of hexanol. On the other hand, MeJ treatment also increased the terpene fraction, whereas Nano-MeJ, at the applied concentration, did not increase it in any of the seasons. In summary, although not all families of volatile compounds were increased by Nano-MeJ, the Nano-MeJ treatment generally increased the volatile composition to an extent similar to that obtained with MeJ used in a conventional way, but at a 10 times lower dose. Therefore, the use of nanotechnology could be a good option for improving the quality of wines from an aromatic point of view, while reducing the necessary dosage of agrochemicals, in line with more sustainable agricultural practices.

Effects of Girdling and Foliar Fertilization with K on Physicochemical Parameters, Phenolic and Volatile Composition in ‘Hanxiangmi’ Table Grape

Aroma is one of the most important indicators of grape quality. Girdling and foliar fertilization with K (K2O) are common agronomic practices applied to improve berry quality in grape production. However, little is known about its effect on the accumulation and biosynthesis of the entire aromatic profile. Our study was aimed to explore the influences of girdling and foliar fertilization with K (alone or in combination) on the general properties, phenolic composition, volatile free aroma compounds, spatial and temporal expression of terpene-related genes and sensory properties in ‘Hanxiangmi’ table grape. In this study, we found that girdling and foliar fertilization with K (alone or in combination) facilitated fruit enlargement and increased the accumulation of phenolic compounds in skin. The combination treatment of girdling and foliar fertilization with K significantly promoted the concentrations of total soluble solids (TSS) in the pulp and proanthocyanidins in the berry skin, and had a lower titratable acidity (TA) compared to those of the control. In contrast, girdling treatment alone increased the concentrations of titratable acidity. Volatile free aroma composition analysis revealed that the combination treatment increased the volatile compounds and concentrations significantly, most notably in terpenes, such as nerol, citronellol and linalool. Spatial and temporal expression analysis showed that the expression level of VvDXS was significantly correlated with linalool and total terpenes concentrations, as a result of which, we speculated that VvDXS is the candidate gene for the regulation of important grape terpenes. We hope that our results can direct farmers to better apply girdling and foliar fertilization with K in grape production.

Biogenic volatile organic compounds in the grapevine response to pathogens, beneficial microorganisms, resistance inducers, and abiotic factors

The synthesis of volatile organic compounds (VOCs) in plants is triggered in response to external stimuli, and these compounds can migrate to distal tissues and neighbouring receivers. Although grapevine VOCs responsible for wine aroma and plant-insect communications are well characterized, functional properties of VOCs produced in response to phytopathogens, beneficial microorganisms, resistance inducers, and abiotic factors have been less studied. In this review, we focused on the emission patterns and potential biological functions of VOCs produced by grapevines in response to stimuli. Specific grapevine VOCs are emitted in response to the exogenous stimulus, suggesting their precise involvement in plant defence response. VOCs with inhibitory activities against pathogens and responsible for plant resistance induction are reported, and some of them can also be used as biomarkers of grapevine resistance. Likewise, VOCs produced in response to beneficial microorganisms and environmental factors are possible mediators of grapevine-microbe communications and abiotic stress tolerance. Although further functional studies may improve our knowledge, the existing literature suggests that VOCs have an underestimated potential application as pathogen inhibitors, resistance inducers against biotic or abiotic stresses, signalling molecules, membrane stabilizers, and modulators of reactive oxygen species. VOC patterns could also be used to screen for resistant traits or to monitor the plant physiological status.

Transcriptomics Integrated with Metabolomics Reveals the Effect of Cluster Thinning on Monoterpene Biosynthesis in 'Muscat Hamburg' Grape

Monoterpenes are crucial to floral and fruit aromas in grapes and wines. Cluster thinning is a common practice for improving grape quality. Using Vitis vinifera cv. Muscat Hamburg, the effects of three cluster-thinning regimes on the biosynthesis and accumulation of monoterpenes from véraison to harvest were investigated at the transcriptomics and targeted metabolomics levels. It was observed that more intense thinning produced higher concentrations of total monoterpenes, particularly in their bound forms. The numbers of differentially expressed genes among the three treatments were 193, 200, and 238 at the three developmental stages. In total, 10 modules were identified from a weighted gene correlation network analysis, and one module including 492 unigenes was associated with monoterpene metabolism. These findings provide new insights into the molecular basis of the relationship between cluster thinning and monoterpene biosynthesis in Muscat Hamburg grape. Cluster thinning could be carefully considered for its application in production.

Implication of Row Orientation Changes on Fruit Parameters of Vitis vinifera L. cv. Riesling in Steep Slope Vineyards

Row orientation, among others, is a crucial factor in determining grapevine performance and health status, thus affecting berry components that form the basis of the later wine profile. However, the literature about the impact of changes in row orientation at steep slope sites on grapevine fruit composition as well as the differentiation between canopy sides hardly exists. Thus, the aim of this work was to gain knowledge about the impact of row orientation in steep slope vineyards on selected primary and secondary metabolites in berries of Vitis vinifera L. cv. Riesling. Samples were taken from both canopy sides of different row orientations of terraced and downslope vineyards in steep slopes. Free amino acids in the juice and flavonols in the berry skin had a positive correlation to sunlight exposure. Furthermore, grapevines showed adaptations to constantly higher light conditions, e.g., physiologically in reduction in chlorophyll content or protective mechanisms resulting in a lower susceptibility to sunburn damage. Thus, grapevine fruit parameters are affected by row orientation change in steep slopes.

Free and Immobilised β-Glucosidases in Oenology: Biotechnological Characterisation and Its Effect on Enhancement of Wine Aroma

In grapes, monoterpenes and norisoprenoids are in the form of non-volatile compounds, flavourless glycosides which could enhance the aroma of wines after its hydrolysis using β- glucosidases enzymes. It is known that the use of immobilised enzymes offers advantages such as reusability and easy recuperation. In this study, a commercial β-glucosidase was immobilised by absorption in sodium alginate. Biotechnological characteristics and terpen hydrolysis (hydrolysis aroma precursors) in muscat wines were studied after treatment with both free and immobilised commercial β- glucosidase with two different concentrations. It was revealed that both forms shared an optimal pH (4.5) and a maximum temperature (64°C), even an increment on the activity between 40and 60°C. A similar Km value has been determined while Vmax from the immobilised enzyme was higher than the free (3.35 and 2.52 μmol min^–1 mg^–1, respectively). Additionally, the immobilised enzyme showed a better hydrolytic activity during 24 h, and its reusability has been proven. Regarding enzymatic hydrolysis in grape must, the best results were observed for the highest concentration of free β-glucosidase although glucose release was also determined for the immobilised enzyme along the days. In contrast, maximum activity was reached by the immobilised β-glucosidase in less time but in no case equalled the free ones. Finally, volatile compound liberation in wines treated with free or immobilised enzymes was analysed using HRGC-MS. Liberation for both enzymes and the greatest concentrations of some volatiles were detected when a double dose of the free β-glucosidase was used. Nevertheless, the wines treated with the immobilised β-glucosidase showed a high concentration of some volatile compounds such as nerol or geraniol.

Assessment of Volatile Aromatic Compounds in Smoke Tainted Cabernet Sauvignon Wines Using a Low-Cost E-Nose and Machine Learning Modelling

Wine aroma is an important quality trait in wine, influenced by its volatile compounds. Many factors can affect the composition and levels (concentration) of volatile aromatic compounds, including the water status of grapevines, canopy management, and the effects of climate change, such as increases in ambient temperature and drought. In this study, a low-cost and portable electronic nose (e-nose) was used to assess wines produced from grapevines exposed to different levels of smoke contamination. Readings from the e-nose were then used as inputs to develop two machine learning models based on artificial neural networks. Results showed that regression Model 1 displayed high accuracy in predicting the levels of volatile aromatic compounds in wine (R = 0.99). On the other hand, Model 2 also had high accuracy in predicting smoke aroma intensity from sensory evaluation (R = 0.97). Descriptive sensory analysis showed high levels of smoke taint aromas in the high-density smoke-exposed wine sample (HS), followed by the high-density smoke exposure with in-canopy misting treatment (HSM). Principal component analysis further showed that the HS treatment was associated with smoke aroma intensity, while results from the matrix showed significant negative correlations (p < 0.05) were observed between ammonia gas (sensor MQ137) and the volatile aromatic compounds octanoic acid, ethyl ester (r = -0.93), decanoic acid, ethyl ester (r = -0.94), and octanoic acid, 3-methylbutyl ester (r = -0.89). The two models developed in this study may offer winemakers a rapid, cost-effective, and non-destructive tool for assessing levels of volatile aromatic compounds and the aroma qualities of wine for decision making.

Increased Varietal Aroma Diversity of Marselan Wine by Mixed Fermentation with Indigenous Non-Saccharomyces Yeasts

The common use of commercial yeasts usually leads to dull wine with similar aromas and tastes. Therefore, screening for novel indigenous yeasts to practice is a promising method. In this research, aroma discrepancies among six wine groups fermentated with indigenous yeasts were analyzed. Three Saccharomyces yeasts (FS36, HL12, YT28) and three matched non-Saccharomyces yeasts (FS31, HL9, YT2) were selected from typical Chinese vineyards. The basic oenological parameters, aroma compounds, and sensory evaluation were analyzed. The results showed that each indigenous Saccharomyces yeast had excellent fermentation capacity, and mixed-strain fermentation groups produced more glycerol, contributing to sweeter and rounder taste. The results from GC-MS, principal components analysis (PCA), and sensory evaluation highlighted that the HL mixed group kept the most content of Marselan varietal flavors such as calamenene and β-damascone hereby ameliorated the whole aroma quality. Our study also implied that the indigenous yeast from the same region as the grape variety seems more conducive to preserve the natural variety characteristics of grapes.

Crop Load and Plant Water Status Influence the Ripening Rate and Aroma Development in Berries of Grapevine (Vitis vinifera L.) cv. Cabernet Sauvignon

Wine made from grapes subjected to accelerated ripening, an increasingly frequent phenomenon occurring in many wine regions due to peaks of heat and water stress, displays higher alcohol levels and lacks balance with color and flavor compounds. Herein, the rate of sugar accumulation of grapes was manipulated by varying the crop load and irrigation regime and the development of secondary metabolites was monitored by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). A 3-week delay in ripening correlated to an increase in the concentration of some monoterpenes and norisoprenoids and a greater decrease of green aroma compounds. Delayed ripening had a positive impact on the phenolic composition of grapes, displaying higher contents of total anthocyanins, total phenolics, quercetin glycosides, and polymeric pigments. A map of the chemical composition of grapes close to harvest allowed discrimination of compounds mainly responsive to delayed ripening from those driven by crop load or irrigation.