Dimensioni degli acini e caratteristiche qualitative della cv Shiraz.

The influence of berry size and cluster exposure on berry composition and on grape quality was studied, taking into account berry size variability in a irrigated vineyard of cv Syrah, located in a temperate area of South of Africa. From two sides of the canopy (east and west) berries of 45 clusters divided in three replicates were weighed to create four categories: (1. less or equal to 1.5 g; 2. between 1.51 and 2.00 g; 3. between 2.01 and 2.50 g; 4. higher than 2.50 g). The ratio skin weight/berry weight did not change with increasing berry size while the ratio seed weight/berry weight changed. Total anthocyanins were analysed by spectrophometry and anthocyanin profile by HPLC. About anthocyanins, varying results were obtained if values were expressed as mg/berry or mg/g of skin, mg/kg of grape and mg/cm2 of skin. The quantity of total anthocyanins changed positively with increasing berry weight if expressed in mg/berry, while this remained almost similar if it was expressed in mg/cm2 of skin. The polyphenols, instead, diminished with berry weight if the values were expressed in mg/kg of grape and in mg/g of skin. Anthocyanins expressed in mg/kg of grape and in mg/g of skin was correlated positively to the number of berries and to surface of total skin in one kilo of grape. In this study, the largest berries had less quality and in conclusions to have a better quality, it seems important to reduce berry weight and, in general, berry size variability.