Appraisal of wine color and phenols from a non-invasive grape berry fluorescence method

Abstract

Aims: To investigate the relationships between the anthocyanin content of Vitis vinifera L. cvs. Tempranillo and Graciano grapes, determined in the vineyard and in the winery by a non-invasive fluorescence sensor, and the final wine color and phenolic traits. Methods and results: Grape anthocyanin and phenol measurements were conducted with a hand-held, non-destructive fluorescence-based proximal sensor, in the vineyard (on clusters hanging on the vine) and at the winery (on harvested clusters in boxes) in two seasons. The anthocyanin fluorescence indices, ANTH_RG and FERARI, were found to significantly correlate with the wine color density (R2 ranged from 0.51 to 0.82) and total phenol index (R2 ranged from 0.44 to 0.87), regardless that the measurements were made in the vineyard or in the winery. Similarly, the CIELAB parameters defining lightness (L*), hue angle (h*) and coordinate b* (yellow-blue component of the wine tonality) also showed significant relationships (R2 ranged from 0.55 to 0.74) with ANTH_RG and FERARI indices in very young wines. Conclusion: This preliminary study showed that satisfactory estimation of the final wine color and phenolic characteristics can be obtained from fast, non-destructive measurements in grapes, using a fluorescence-based sensor, either in the vineyard or in the winery. Significance and impact of the study: This is the first work showing the capabilities of the chlorophyll fluorescence of grapes to estimate the final wine color and phenolic traits. This information could help the wine industry make more informed decisions regarding selective harvest and winemaking in a fast and cost-effective way.

Keywords

• wine color density
• total phenol index
• fluorescencebased sensor
• CIELAB
• grapevine