Non-destructive fluorescence sensing for assessing microclimate, site and defoliation effects on flavonol dynamics and sugar prediction in Pinot blanc grapes

Abstract

In an era of growing international competition in modern viticulture, the study and implementation of innovative technologies to increase the production of high-quality grapes and wines are of critical importance. In this study, the non-destructive portable sensor Multiplex, based on fluorescence sensing technique, was applied to evaluate grape maturity parameters and flavonol content of the understudied Pinot blanc variety. The effects of environmental and agronomical factors on flavonol content of Pinot blanc grapes were investigated in eight vineyards characterised by different microclimatic and agronomic conditions. Furthermore, the direct impact of canopy management treatment on the flavonol dynamics of the grapes oriented in the four cardinal directions was assessed. Results highlight the positive role of moderate temperatures and direct sunlight exposure on Pinot blanc flavonol content; however, no direct vineyard-elevation effect was observed. The ability to modulate and evaluate the flavonol content in field represent crucial factors because of their potential effect on flavonoids-dependent wine characteristics, such as stability and ageing. In the present study, for the first time, two calibration curves were reported for pre- and post-veraison periods between flavonol indices and the berry skin flavonol content and a good correlation was observed between Multiplex measurement and the total polyphenolic content of grape juice. Moreover, the strong correlation between the chlorophyll index with grape juice sugar content and titratable acidity revealed the practical application of non-destructive sensors to predict the optimal harvest time for Pinot blanc grapes. In conclusion, the non-destructive fluorescence sensor Multiplex is a high-potential tool for innovative viticulture, for evaluating grape skin composition variables in white grape varieties.

Analyses of Vineyard Microclimate in the Eastern Foothills of the Helan Mountains in Ningxia Region, China

“…Overall, the field microclimate observation data more accurately reflected the characteristics of the vineyard microclimate than the national reference station data. This result is consistent with a previous study that listed the temperature variation characteristics between a microclimate station and a weather station and concluded that microclimate station data could better represent vineyard climate [11,[20][21][22][23][24][25].…”

Vine Foliar Treatments at Veraison and Post-Veraison with Methyl Jasmonate Enhanced Aromatic, Phenolic and Nitrogen Composition of Tempranillo Blanco Grapes

“…Flavonoid synthesis is conditioned by the expression of the enzyme flavanoid 3’5’-hydroxylase in white grape varieties, which limits the synthesis to quercetin, kaempferol and isorhamnetin compared to red grape varieties, where myricetin, laricitrin and syringetin are also synthesised [ 41 ]. Flavonols are yellow pigments that contribute to the colour of white varieties and provide several positive effects on human health due to their antioxidant activity [ 39 , 42 ].…”