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

In an era of growing international competition in modern viticulture, the study and implemen-tation of innovative technologies to increase the production of high-quality grapes and winesare of critical importance. In this study, the non-destructive portable sensor Multiplex, basedon fluorescence sensing technique, was applied to evaluate grape maturity parameters andflavonol content of the understudied Pinot blanc variety. The effects of environmental andagronomical factors on flavonol content of Pinot blanc grapes were investigated in eightvineyards characterised by different microclimatic and agronomic conditions. Furthermore,the direct impact of canopy management treatment on the flavonol dynamics of the grapesoriented in the four cardinal directions was assessed. Results highlight the positive role ofmoderate temperatures and direct sunlight exposure on Pinot blanc flavonol content; how-ever, no direct vineyard-elevation effect was observed. The ability to modulate and evaluatethe flavonol content in field represent crucial factors because of their potential effect on fla-vonoids-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 periodsbetween flavonol indices and the berry skin flavonol content and a good correlation wasobserved between Multiplex measurement and the total polyphenolic content of grape juice.Moreover, the strong correlation between the chlorophyll index with grape juice sugar con-tent and titratable acidity revealed the practical application of non-destructive sensors topredict the optimal harvest time for Pinot blanc grapes. In conclusion, the non-destructivefluorescence sensor Multiplex is a high-potential tool for innovative viticulture, for evaluatinggrape skin composition variables in white grape varieties.