Oenological features of Sangiovese wine from vinification of whole grape berries

Abstract

The present study was performed in a traditional winery located in the viticultural area of Brunello di Montalcino, Siena, Italy, in the vintage 2015. Actually, in this winery Sangiovese grape musts are fermented in large oak barrels by a single strain of Saccharomyces cerevisiae previously isolated in the same winery. Pumping over operations are carried out once or twice a day until the end of alcoholic fermentations. The aim of this work was to investigate on the oenological properties of Sangiovese wine produced with the traditional winemaking process adopted by the winery under study obtained from the fermentation of whole berries compared to that from crushed grape must. In particular, two lots of 65q of Sangiovese grapes from the same 3ha vineyard were vinified in 150hL oak barrels. Grapes of the first lot were destemmed using a vibrating destemmer that was able to maintain the berry integrity, the others with a traditional crusher-destemmer. After barrels filling, the temperature of whole berry grape must was lower than that of crushed grape must (22°C vs 24°C). The growth of S. cerevisiae strain, inoculated at 5×10^5cell/mL, was slower in whole berry grape must due to the lower mass temperature and the progressive rupture of berries which caused a sort of dilution of yeast population during their exponential growth phase. Indeed, the maximum population density was reached at the third day of fermentation in the crushed grape must (over 8×10^7 cell/mL) while in the whole berry must was reached at day 6 (about 3.5×10^7cell/mL). The warming profile of crushed grapes vinification was faster and reached higher temperature (3.7°C/day up to Tmax of 38.9°C at day 4) than that recorded in whole berry vinification (1.7°C/day up to Tmax of 33.8°C at day 7). In the former, the yeast population dropped rapidly as a consequence of high temperature and high ethanol content (about 11% at day 4) leading to a faster decrease in mass temperature and making it necessary a second inoculum of the S. cerevisiae strain at day 11 to ensure the completion of the alcoholic fermentation. Conversely, the progressive rupture of cooler berries in the whole berry vinification limited the temperature rise, favored the yeast activity, and lead to a slower decrease of mass temperature after day 8 at which about 95% of sugars were fermented. Wines were racked at day 26 (crushed grapes) and 27 (whole berry grapes). Residual sugars were below 1g/L with an ethanol content ranging from 13.8 to 13.5% in crushed and whole grapes wines, respectively. No differences were found on color intensity and total phenolic index. However, wine from crushed grapes vinification possessed higher contents of hydroxybenzoic acids (+27%) and flavan-3-ol monomers (+20%) whereas wine produced by whole berry vinification were characterized by higher contents of anthocyanin glucosides (+33%) and flavonols (+41%). Such differences are potentially able to influence several long-term sensory quality.