Use of response surface methodology for the assessment of changes in the volatile composition of Moscato bianco (Vitis vinifera L.) grape berries during ripening

• Changes in the terpene composition of grape berries were evaluated during ripening.
• The simultaneous effect of sampling time and berry density on terpenes was studied.
• Response surface methodology was used to assess the combined effect time-density.
• Grape density was the main factor affecting the total terpene concentration.
• The sampling strategy may suppose different aroma quality of grape berries.

The changes in the volatile composition of Moscato bianco grapes were evaluated during ripening. Grape berries were sampled for five weeks (16–20 °Brix) and sorted for each date in ten density classes (1.05–1.12 g/cm3). The highest total concentration of free terpenes was found at 19.3 °Brix; however, total concentration of the bound fraction increased significantly throughout ripening. Response surface methodology was used to assess the simultaneous effect of sampling time and berry density on the volatile composition, which was satisfactorily fitted to regression models for some key terpene compounds. Total free and bound terpenes were more affected by grape density than by sampling date. The same behaviour was observed for free and bound linalool and bound nerol, whereas the stronger effect of sampling date was exhibited for bound t-rose oxide, c-rose oxide and geraniol. The results showed that the sampling strategy impacted strongly on the aroma quality of berries.