Changes in the phenolic composition, phenol extractability indices, and mechanical properties occur in grape berries during the ripening process, but the heterogeneity of the grapes harvested at different ripening stages affects the reliability of the results obtained. In this work, these changes were studied in Nebbiolo grapes harvested during five consecutive weeks and then separated according to three density classes. The changes observed in chemical and mechanical parameters through the ripening process are more related to berry density than harvest date. Therefore, the winemaker has to select the flotation density according to the objective quality properties of the wine to be elaborated. On the other hand, the stiffer grapes were associated with a higher accumulation of proanthocyanidins. The harder grapes provided the higher concentration and extractability of flavanols reactive to vanillin, whereas the thicker ones facilitated the extraction of proanthocyanidins.

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Grapes were subjected to culture dependent and independent analysis. By plate count on WLN medium a yeast load of about 10 2 colony forming units (cfu)/mL was determined on the grapes. A total of 206 isolates were identified by using two different molecular approaches. The results obtained through the two identification techniques, PCR-RFLP analysis of the 5.8S-ITS rRNA region and PCR-DGGE coupled with sequencing of the 26S rRNA gene, resulted highly reproducible and comparable, confirming these methods as two reliable identification tools in the study of wine yeast ecology. Through both techniques, a mycobiota mainly constituted by Aureobasidium pullulans (73% of the isolates), followed by Rhodotorula glutinisCryptococcus carnescens (1%) was described. Moreover, DNA and RNA extracted directly from grapes were subjected to PCR-DGGE confirming the presence of A. pullulans. H. uvarum and Starmerella bacillaris (synonym Candida zemplinina) were also detected.