Evolution of the Phenolic Content and Extractability Indices During Ripening of Nebbiolo Grapes from the Piedmont Growing Areas over Six Consecutive Years

Abstract

The phenolic composition and extractability indices of grape berries play a key role in assessing red
wine quality because the relationship between grape phenolic maturity and wine phenolic composition
is well known. In this work, grape quality indices were determined in Nebbiolo grapes from two growing
areas of Langhe (South Piedmont), at different stages throughout the ripening process in six consecutive
years (2004 to 2009), with the aim of evaluating the ripening- and growing area-related changes in the
grape indices separately. The effect of vintage was also investigated. Ripeness data were compared with
analogous data determined in Nebbiolo grapes grown in the Carema area (North Piedmont). The vintage
effect far outweighed any changes in the grape indices introduced by the ripening stage, even those arising
from differences in the production area. In the Langhe and Carema zones, the average berry mass, pH,
total acidity, total anthocyanins extractable at pH 3.2, total flavonoids and non-anthocyanin flavonoids
extractable at pH 1, and the seed maturity index were seasonally dependent. The more ripening-affected
parameters were the technological ones. This work highlights the importance of determining the phenol
extractability, since it provides relevant information that allows improved management of the maceration
stage.