On-vine drying: berries physical-mechanical parameters as varietal markers to assess the aptitude at the icewines production

In Italy, the climatic conditions for the production of icewines are only present in mountain grape-producing environments. In this context, the production of icewines can thus be a major opportunity for companies operating in alpine Regions, in particular when local grape cultivars are exploited. Grape overripening on plant involves numerous physical, histological and biochemical modifications about which still little is known. For this type of withering, the main characteristics required by the cultivars are a high resistance to shattering, to plant fungal diseases and to environmental damages. The evolution during on-vine process of grape mechanical parameters such as skin hardness and thickness or peduncle detach resistance evaluated in this study, can be therefore used as varietal indicators in assessing grapes suitability for the drying on plant process and in consequence in the production of ice wines. The study was conducted on three cultivars (Becuét, Mondeuse and Fumin) growing in Europe mainly in the Western Alps. In each cultivar, during grape dehydration, an skin thickness increase was observed. Also the skin hardness increased, particularly in Becuét berries, in which the break skin force and break skin energy values raised respectively of 0.148N and 0.823 mJ. In contrast, the peduncle detachment force decreased during the drying process and, in Becuét grapes, this occurred after only 15 days. Although having different mechanical properties, the cultivars proved to be suitable for the production of ice wines, and the changes that occur do not preclude the resistance of the berries to shattering and of the berry skins to splitting.