Cluster Thinning and Vineyard Site Modulate the Metabolomic Profile of Ribolla Gialla Base and Sparkling Wines

The impact of fruit thinning on size and quality of fresh-market muscadine berries

BACKGROUND

Achieving a larger berry size accompanied with even ripening are demanded by producers in growing muscadine cultivars. The current study aimed to evaluate the impact of fruit thinning on berry size and quality in two muscadine grape cultivars, 'Triumph' a bronze-fruited cultivar bearing hermaphrodite flowers, and 'Supreme' a dark black-fruited cultivar bearing female flowers. Thinning was performed before bunch closure and only one cluster per cane was retained.

RESULTS

Results indicated a significant interaction of treatments and cultivars on berry weight and berry diameter. In 'Supreme,' berry weight and berry diameter were significantly increased where thinning was performed, and difference in plant yield between thinned and not thinned vines was not significant. For 'Triumph,' thinning had no significant impact on berry weight and diameter, but yield was ultimately reduced. Other physico-chemical characters were not affected by fruit thinning. However, differences were observed between both cultivars for these characters. The values of antioxidant scavenging activity (ASA) and total phenolic content (TPC) were 62.7% and 21.7% higher in 'Supreme' as compared to 'Triumph,' irrespective of the thinning treatments. Being a colored cultivar, 'Supreme' berries have higher anthocyanins than 'Triumph,' which has a negligible amount of anthocyanins. The ASA exhibited a strong positive correlation with TPC and anthocyanin content of muscadine grapes. There was also a significant positive correlation between TPC and anthocyanins.

CONCLUSION

Cluster thinning of some muscadine grape cultivars may improve individual berry size without affecting overall plant yield or the fruit color, firmness, biochemical attributes and bioactive compounds. © 2023 Society of Chemical Industry.

Combined effect of harvest time and postharvest dehydration length on the composition of withered grapes for Sforzato di Valtellina DOCG wine production

BACKGROUND

Sforzato di Valtellina (Sfursat) is a PDO reinforced red wine produced in Valtellina (northern Italy) from partially withered red grapes (Vitis vinifera L.) cv. Nebbiolo. The present study aimed to evaluate the combined influence of different grape ripeness levels and withering length on the chemical composition, mechanical properties, and phenolic profile of Nebbiolo winegrapes from two Valtellina vineyards. During three consecutive vintages (2019, 2020, and 2021), three different technological binomials have been tested: early harvest/long withering (EL), medium-term harvest/medium-term withering (MM), and late harvest/short withering (LS).

RESULTS

At the end of the withering process, EL thesis usually presented the highest values of sugars and acidity. Extractable seed polyphenols showed a decreasing trend by leaving the grapes on the plant longer, and this effect increased considerably after withering with respect to fresh samples. EL and MM evidenced the greater concentration of these compounds expressed on grape weight, particularly for tannins. Instead, skin-extracted total phenolics were less influenced by the harvest time, whereas their concentration increased after withering. The harvest time appears to have a higher impact than the withering length on the final extractable anthocyanin content, although the trend was no stable during the vintages or common for the two vineyards evaluated. EL and MM experienced the highest contents of grape skin tannins in most cases, suggesting that a longer withering increases their concentration.

CONCLUSION

Harvest time and withering length can be modulated according to the desired oenological objective, promoting the valorization of grape potentialities. The choice to harvest the grapes earlier and enhance the withering length should be preferred to obtain wines with higher acidity and phenolic content, more suitable for long-ageing period. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Cluster Thinning Improves Aroma Complexity of White Maraština (Vitis vinifera L.) Wines Compared to Defoliation under Mediterranean Climate

Defoliation and cluster thinning are useful canopy management techniques to modulate grapevine carbon distribution and microclimate. Both techniques are directed to achieve the proper balance between fruit and foliage, and to maximize production of well-ripened fruits and quality wines. We performed five canopy treatments on Maraština grapevine grown at a commercial vineyard in the Vrgorac Valley region of Croatia: three different times of basal defoliation, cluster thinning at the veraison, and an untreated control. The effects of the canopy changes on the chemical composition of grapes and wines were studied. The treatments had variable impacts on yield components and basic wine composition. Volatile aroma compounds in produced wines were analyzed using gas chromatography–mass spectrometry coupled with a mass-selective detector. The concentrations of 70 of the 96 individual volatile compounds were significantly influenced by the canopy technique used. The concentrations of 58 of these compounds were different according the timing of defoliation. Cluster thinning at an intensity of 35% produced wines with more terpenes, esters, higher alcohols, other alcohols, volatile phenolic compounds, lactones, and other compounds than other treatments. Among terpenes, cluster thinning increased terpinen-4-ol, linalool, trans-β-farnesen, and geraniol. Odor activity value analysis revealed 16 volatile compounds that contributed to the aroma of cluster-thinned wines.

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.