Technologies for enhancing the aromatic potential of Malvasia grapes

The aromatic potential of white grapes is mainly present in the skin, consequently the pre-fermentative step becomes crucial for managing the transfer of the different aromatic components into the juice. In Malvasia grape the presence of varietal aromas of different types is recognized which must however be extracted with specific winemaking techniques. In the present study, carried out in some Croatian wineries, traditional and innovative technologies were evaluated, in order to study the response on the aromatic characteristics of the Malvasia wines. The traditional technology was enzyme with pectolytic enzymes also containing β-glycosidases, while the innovative technology was ultrasound on the crushed grapes, a technique recently authorized by the OIV and the EU. The tests with enzymes were carried out by adding the enzymatic preparation at the end of the fermentation, in order to optimize its activity in a medium with a low sugar content. The vinification tests were carried out in real cellar conditions. The results made it possible to verify the effectiveness of the enzymatic intervention which, at an analytical and sensory level, demonstrated positive responses compared to the untreated control. Ultrasound treatment of the crushed grape was used as an emerging technology. The experiments were carried out on a pilot scale, a thesis provided for the two-minute treatment of the crushed grapes with ultrasound and subsequent pressing, the control was instead represented by the 24-hour maceration at 15°C. The analytical data of the total thiols detected on the wines and the sensory evaluations made it possible to evaluate the ultrasound treatment as a valid low-input technique as an alternative to the traditional maceration. Direct effects of ultrasound on thiol precursors were also highlighted, with release of the free thiol fraction without the intervention of yeast β-lyase. The experiences carried out have made it possible to verify the reactivity of Malvasia to the various technological interventions aimed at enhancing the aromatic potential of the grape with a reasoned integration of traditional and emerging techniques. Depending on the oenological objective, there are margins for choosing low-impact techniques to enhance the aromatic potential of Malvasia.