Proximal sensing to assess berry ripening in Mediterranean viticulture

The sugar content as well as the anthocyanin content are useful tools to determine the correct harvest time. The optical portable sensor Multiplex3^® (FORCE-A, Paris, France) is able to screen the colored component of grapes with a rapid and non-destructive method. The aim of this study was to verify the ability of sensor Multiplex3^® in a Mediterranean environment to assess the berry maturation in four red grape cultivars. The study was carried out in two locations situated in Nurra valley (Alghero, NW Sardinia) on four different red cultivars, ‘Cagnulari’, ‘Cabernet Sauvignon’, ‘Cannonau’ and ‘Monica’. During the 2016 season, the SFR_R, ANTH_RB, ANTH_RG and FERARI indices were monitored from veraison to harvest; simultaneously, sugars, pH and total anthocyanins were determined in the laboratory. Different results were obtained in terms of fluorimetric indices and chemical data correlations. The FERARI index showed a good correlation with the anthocyanin concentration derived from spectrophotometric analysis (‘Cagnulari’ ρ=0.72, ‘Cabernet Sauvignon’ ρ=0.84, ‘Cannonau’ ρ=0.77, ‘Monica’ ρ=0.72). The equation obtained for this index can be used to assess berry ripening in Mediterranean viticulture. On the other hand, the ANTH_RG index showed strong inverse correlations with both the anthocyanin content and the berry weight, although not for all the cultivars tested.