Impact of grapes heterogeneity according to sugar level on both physical and mechanical berries properties and their anthocyanins extractability at harvest.

One of the major factors affecting wine quality is the degree of the grapes maturity at harvest time. Cabernet Franc grapes belonging to six different classes of sugar level content (from 176.5 to 258.5 gL-1) at harvest were studied. Their physical proprieties and mechanical behavior were measured using compression and puncture tests. The evolution of anthocyanins extractability was determined. Significant differences were found in grape textural properties and anthocyanins content due to the sugar level content in the different samples of berries tested. It appears that sweetest berries are characterized by a higher extraction yield of anthocyanins (up to + 3.55%) respect to those with a more low sugar content. Furthermore, significant relationships exist between the extractability of anthocyanins and the mechanical and physical attributes of the grape berries. The best correlation coefficients were obtained with physical parameters such as the berry weight and the surface:volume ratio (r = -0.99 and 0.97 respectively) and with double compression test parameters such as hardness, chewiness and springiness (r = -0.90, -0.91 and 0.92 respectively).