Moderate dehydration of 'Syrah' grapes (Vitis vinifera L.) for winemaking

In Europe, the partial dehydration of grapes after harvest for winemaking has been shown to be a process that brings increased concentration of sugar and phenolic compounds in the must, resulting in wines with higher quality However, in Brazil there are a few studies to identify the potential of moderate dehydration of grapes on wine quality. Therefore, this study is aimed to analyze the physicochemical changes (Concentration of Total Soluble Solids (TSS) and Phenolic Compounds (PC)) of 'Syrah' grapes after partial dehydration subjected to two treatments combining two temperatures and one air velocity (T-1=22.9 degrees C/1.79 m s(-1) and T-2 = 37.1 degrees C/1.79 m s(-1)) and relative humidity of 40%. The water loss of the grapes was approximately 14%, and the drying process lasted between 34 to 68 h for treatments T-2 and T-1, respectively. We experimentally and statistically verified that the treatments promoted significant increase in TSS and PC; however, for PC, at the temperature of 22.9 degrees C, the increase accounted for approximately 27%, whereas, for the temperature of 37.1 degrees C, it was only 12%. For TSS, the increase was on average 12.47 +/- 0.9% between both treatments. The results demonstrate that it is possible to dry grapes moderately, thus resulting in improvements in their chemical composition, which can improve the quality of wine.