Antonio Carlomagno

Screening and evolution of volatile compounds during ripening of ‘Nebbiolo,’ ‘Dolcetto’ and ‘Barbera’ (Vitis vinifera L.) neutral grapes by SBSE–GC/MS

Abstract The evolution of pre-fermentative volatiles and of the global aroma potential in three Italian neutral varieties (‘Nebbiolo,’ ‘Barbera’ and ‘Dolcetto’) was assessed from véraison to harvest by SBSE–GC/MS. C6 and C9 compounds, benzene derivatives, bound monoterpenes and sesquiterpenes showed differences among varieties in quantity and profiles during berry ripening. Quantitatively, the most of total monoterpenes, C-13 norisoprenoids and sesquiterpenes were detected after acid hydrolysis. Among pre-fermentative norisoprenoids, exclusively β-ionone was detected with different kinetics among varieties. Monoterpene accumulation started around véraison with the exception of (E)-geranylacetone, whose content was already high at véraison. (E)-Geranylacetone, deriving from the degradation of carotenoids, could become a target molecule to study indirectly the accumulation of carotenoids. Data allowed to measure the global aroma potential and the pre-fermentative volatiles of grapes: result interpretation suggested a number of implications on biosynthetic processes that have been addressed.

Improved fluorescence-based evaluation of flavonoid in red and white winegrape cultivars

Background and Aims Modern viticulture requires robust, fast, non-destructive methods to assess berry composition. We tested a chlorophyll fluorescence screening method to estimate berry phenolic substances. Methods and Results We focused on anthocyanin and flavonol in red and white cultivars. The ANTH_RG index was dependent on the cultivar anthocyanin profile. In Nebbiolo, in which dihydroxylated anthocyanins prevail, ANTH_RG was 2.4 times higher than in Barbera, in which trihydroxylated anthocyanins prevail. Considering the profiles of the two cultivars at similar anthocyanin concentration and their relative in vitro absorbance, a bathochromic shift of 10 nm emerged, which can explain the different screening effect exerted by anthocyanin on chlorophyll fluorescence. As to flavanols, we propose the calibration of a new spectroscopic index, the FLAV_UV, in coloured and white berries, finding good correlation with flavonol concentration determined analytically (R2 higher than 0.7). Conclusions Spectroscopic indices can estimate the concentration of anthocyanin and flavonol in grape berries. Significance of the Study A calibration curve for Nebbiolo, which has a distinctive anthocyanin profile, and the calibration of a new index, the FLAV_UV, able to estimate flavonol concentration in both red and white cultivars, are described for the first time. These indices can effectively be applied for non-destructive assessment of grape flavonoid.