Comparison of grape harvesting and sorting methods on factors affecting the must quality

This study compared two harvesting techniques (manual and mechanical) and three grape sorting methods (no sorting, manual, and densimetric) in attempts to obtain high-quality must. The trials were carried out in 2009 and 2010 in Tuscany, Italy. The effectiveness of the harvest-sorting chain was assessed on two parameters. Sub-standard berries (SSB) is the percentage of berries, which do not meet quality standards that enter the winemaking process, and material other than grape (MOG) is a measure of the cleanliness of the berries entering the process. In the two years the trial was run the grape maturation level was widely different; in 2009 the vintage was more far mature than in 2010. With respect to SSB content and harvesting methods, in 2009 (more mature grapes) hand-picking reduced SSB content, while in 2010 there were no differences between the two harvesting methods. In both years, densimetric sorting reduced SSB content, while there were no significant differences between no sorting and manual sorting. In terms of MOG content, both harvesting and sorting results were inconsistent. In 2009, MOG was lower in mechanically harvested grapes; while in 2010 it was lower in hand-picked grapes. As for sorting methods, in 2009 there were no differences in MOG, while in 2010 mechanical sorting produced better results. Our results question whether the post-harvest sorting techniques used by many estates are effective; particularly as the question has received little attention and no previous research has compared methods. Secondly, our study contributes to the debate on the effects of harvesting technique on wine quality.