Major phenolic and volatile compounds and their influence on sensorial aspects in stem-contact fermentation winemaking of Primitivo red wines.

In red winemaking de-stemming is crucial since the stems contain polymeric phenolic compounds responsible for the astringency of wine. Wine such as Primitivo has low phenolic constituents and tannins and stems affect aroma, taste body and olfactory characteristics. The aim of the study was to evaluate the effects of presence of stems during fermentation on polyphenolic, volatile compounds and sensory characteristics of wine. Primitivo grapes vinified in presence of different percentage of stems: 100 % de-stemmed (D100), 75 % de-stemmed (D75) and 50 % de-stemmed (D50). Results confirmed that the wines vinified in presence of stems were higher in tannins, flavans, to vanillin and proanthocyanidins, colour intensity with lower anthocyanins. The presence of stems during fermentation conferred more structure and flavour to wines. They facilitated must aeration thus promoting synthesis of higher alcohols and ethyl esters by yeast. In particular, a higher content of hexan-1-ol, hex-3-en-1-ol and 2-phenyl ethanol in D50 and D75 gave the wines that suggest green grass, herb and floral. Wine from D75 seemed to be better than D50 in terms of volatile compounds as well as fruity, floral and balsamic components preserved, without any unpleasant taste of long chain fatty acids found in D50.