Evolution of free and bound volatile aroma compounds and phenols during fermentation of Muscat blanc grape juice with and without skins

Recently, various technologies which utilise fermentation with skins have been developed for obtaining distinct white wines. This study first reports the dynamic changes of volatiles and phenols that occur during skin fermentation in white winemaking. Volatiles were analysed by solid-phase extraction (SPE), solid-phase microextraction (SPME) and gas chromatography (GC), and phenols by ultra-performance liquid chromatography (UPLC), both with mass spectrometric detection. Monoterpenols increased during the first 3 days of skin fermentation, after which certain glycosides decreased, but were higher than in control. The presence of skins reduced ho-trienol, beta-damascenone, acids and esters. After a 1-3 days lag phase, skin fermentation caused a constant increase of most phenols. It was estimated that skin fermentation up to 1-3 days might be beneficial for monoterpenol varietal aroma, which should be re-evaluated through further studies. Longer durations promoted phenol extraction more strongly, which is possibly suitable for obtaining more distinct wines or blending components