 IVES 9 IVES Conference Series 9 Macrowine 9 Macrowine 2021 9 Grapevine diversity and viticultural practices for sustainable grape growing 9 Application of treatments to delay the ripening of grape varieties cultivated in valpolicella

Application of treatments to delay the ripening of grape varieties cultivated in valpolicella

Abstract

AIM: Winegrape cultivars are particularly sensitive to temperature and recent changes in climate have advanced the onset of berry ripening, resulting in unbalanced fruit composition at harvest. High temperatures during ripening result in berries with increased sugar concentration, reduced acidity and colour and unwanted or underdeveloped aroma compounds. To reduce the negative effects of climate change, several adaptation strategies, represented especially by viticultural practices, have been proposed. In this work we tested and compared the effect of two different treatments aimed to delay ripening of the most important grape varieties cultivated in Valpolicella (Verona, Italy).

METHODS: Clusters of Corvina and Corvinone, cultivated in Valpolicella, cordon trained, cane pruned, were treated one week before veraison with 1-Naphthaleneacetic acid (NAA), a synthetic auxin. On another block of vines of the same cultivars in the same vineyard, a postveraison defoliation treatment was applied, with the effect of removing about 30-40% of the leaves thus creating a vertical window without leaves above the bunch area. The dynamic of the main ripening parameters was monitored over the course of maturation and yield and yield components were determined at harvest.

RESULTS:Leaf removal had a very limited effect on delaying the accumulation of sugars in berries, which was the main scope of the trial, compared to berries from untreated vines. On the other hand, the NAA treatment greatly impacted the ripening dynamic of both varieties, postponing the accumulation of sugars and anthocyanins and the decrease in acidity. The effect was more pronounced in Corvinone than in Corvina.

CONCLUSIONS

The results evidenced that a relevant delay of ripening time can be obtained by treating clusters of the main grape varieties cultivated in Valpolicella with auxin-based products. On the contrary, the leaf defoliation treatment only weakly affected the ripening dynamics, possibly due to the remobilization of reserves from the perennial organs of the plant.

DOI:

Publication date: September 2, 2021

Issue: Macrowine 2021

Type: Article

Authors

Giovanni Battista Tornielli

University of Verona, Ron SHMULEVIZ, University of Verona

Contact the author

Keywords

climate change, valpolicella, ripening, auxin, defoliation

Citation

Différenciation mésoclimatique des terroirs alsaciens et relation avec les paramètres du milieu naturel

The influence of climatic conditions on the development of the vine and on the quality of the wines no longer needs to be demonstrated at the scale of the vineyard, by the regional climatic characteristics, determining on this scale the viticultural potentialities (Huglin, 1978; Branas, 1946; Riou et al ., 1994); but also on a local scale, at the level of the basic terroir unit (Morlat, 1989), by the landscape differentiation of the natural environment inducing climatic variability within the same vineyard, and partly explaining differences in functioning of the vine, in connection with the processes of maturation and the quality of the wine (Becker, 1977 and 1984; Morlat, 1989 and Lebon, 1993a). According to these authors, the climatic diversity in a wine region constitutes in addition to the edaphic component, an important component of characterization of the Basic Terroir Units (UTB).

What is the best soil for Sangiovese quality wine?

Sangiovese is one of the main cultivar in the Italian ampelographic outline and it occupies more than 60% of total vineyard surface in the Tuscany region. It is also well known that the environmental

Preliminary characterisation of mannoproteins from different wine yeast strains and impact on wine properties

Mannoproteins (MPs) are released from the yeast cell wall during alcoholic fermentation and aging on the lees, and influence aspects of wine quality such as haze formation and colour stability. Yet, as this is a slow process with microbiological and sensory risks, the exogenous addition of extracted MPs poses an efficient alternative. While Saccharomyces cerevisiae has long been studied as a prominent source for MPs extraction, their structure and composition greatly differ between yeast species. This may influence their behaviour in the wine matrix and subsequent impact on wine properties. However, although wine yeast species other than S. cerevisiae possibly present an untapped source of MPs, they are still ill-characterised in terms of chemical composition and influence on wine.

Study of the Interactions between High Molecular Weight Salivary Proteins and Red Wine Flavanols.

Astringency has been defined by the American Society for Testing Materials as “the complex of sensations due to shrinking, drawing or puckering of the epithelium as a result of exposure to substances such as alums or tannins”. Regarding the importance of astringency in wine consumer acceptance, elucidating the molecular mechanisms underpinning this complex sensation represents an important goal for scientists. Although different mechanisms have been described (Gibbins & Carpenter, 2013), the salivary protein precipitation is still the most accepted theory. According to this, wine astringency perceived in the oral cavity is originally attributed to the interaction and subsequence precipitation of salivary proteins by wine tannins –mainly flavanols–.

How do different oak treatment affect the sensory composition of Chenin blanc wines over time?

Wooden barrels have been the preferred method for oak maturation for wines, but the use of alternative oak products, such as staves and oak chips have increased in South Africa due to lower production costs. This study investigated the effect of different oak products used during fermentation and ageing on the sensory profile, degree of liking and perceived quality of a South African Chenin blanc wine. The different wine treatments included an unoaked tank control wine, wines matured in 5th fill barrels, wines matured in new barrels from three different cooperages, and wines matured in 5th fill barrels with stave inserts from two different cooperages.