Implications of berry size variation of Vitis vinifera L. cv. Syrah

Abstract

Berry size has always been considered a quality factor for wine production, but size variation is a reality in commercial vineyards. In this study, Syrah (clone SH 9C) grapes from a single vineyard, located in the semi-arid Breede River Valley of South Africa (close to Robertson), were sorted into three different berry size groups, i.e. Small (< 13mm), Medium (13-14mm) and Large (> 14mm). Berries in the smaller category were present in the highest numbers, whereas the large group was present in the lowest percentage. Berry physical characteristics (mass, volume, skin area) increased with size. In 2012 values were lower than in 2011, showing the differences between seasons, despite the similarity in trends. Positive correlations were found between berry mass, berry volume, berry skin area and dry skin mass, whereas berry number per kg grapes were negatively correlated to these variables. Results indicated that berry growth/final size is not simply determined by water accumulation. The skin surface area:berry volume ratio seems to be a good indicator of the dilution effect associated with increasing size; large sized berries presented the lowest values in both years. This ratio may also be indicative of the impact of berry skin composition on juice content during crushing. In 2012 grapes were harvested at higher soluble solid levels than in 2011. Large-sized berries had lowest values in both 2011 and 2012. Titratable acidity and pH were in all situations lower and higher, respectively, than what would be preferred in a healthy fermentation and were adjusted. In general, whole berry total anthocyanin contents showed the typical decrease in concentration and increase per berry from small to larger berries in both years. The study supports the making of distinctive wines of different styles in a uniformly managed vineyard, irrespective of naturally occurring berry variation.