Vitis v. corvina grapes composition and wine sensory profile as affected by different post harvest withering conditions

Abstract

Context and purpose of the study – In Valpolicella area (Verona – Italy) Vitis vinifera cv. Corvina is the main wine variety to obtain, after grape withering, Amarone wine: this study was carried out in order to compare two different grape dehydration conditions with the aim of verifying the final composition of Corvina dried grapes and the organoleptic profile of corresponding Amarone wine.

Material and methods – To obtain Amarone wine, Corvina grapes before vinification has to be stored in dehydrating room in order to achieve at least the 30% weight loss. In our experiment (2016/17) we harvested Corvina grapes from the same vineyards but before vinification we used two different withering conditions: i) room with natural air movement forced by opening the windows mainly during the day and ii) room equipped with mechanical air movement system (fans) and air humidity artificial control (around or below 70/75%). In both conditions grape has been left since their 30% weigh loss. Berry macro-composition (sugar, acids, pH) and micro-composition (total polyphenols, anthocyanins, stilbenes, aroma compounds) has been detected for the two grapes postharvest management and the two vinification has been done too.

Results – The healthy berries status did not signed any differences. In artificial conditions grape lost 30% weigh 15/25 days before the natural ones, sugar enrichment was not strictly linked with the water loss, but it was more related with the withering conditions and ripeness stage at harvest. Anthocyanins skin content resulted higher or slightly higher in natural conditions but anthocyanin extractability are equal. Stilbenes compound (trans resveratrol, trans piceide, δ viniferina, etc) are higher in grapes dried in artificial conditions. This latter result could be linked to less stress responses that natural condition impose to berry cells. The total aromatic compounds resulted more pronounced in grapes dried in natural conditions; the single chemical compounds that resulted in higher quantity were: nerolo, geraniolo, 3-OH-β-damascenone, vomifoliolo, guaiacolo, metilsalicilato, alcolbenzilico, eugenolo, acetovanillone. The differences were clearly in favour of natural withering system especially in 2015 and 2017. In terms of wine sensory profile the wine obtained with grape dehydrated in natural room has been preferred for its higher pronounced body and structure, for its spices, fresh and ripe red fruit flavour. The results underline that postharvest dehydration conditions have a significant impact on general bunch metabolism and even if the water loss increases the solute concentration, physiological and biochemical processes may affect berry composition and wine character under different dehydrating choices.