Comparison of Proanthocyanidins with Different Polymerisation Degrees among Berry Skins of ‘Shiraz’, ‘Cabernet Sauvignon’, and ‘Marselan’

Proanthocyanidins in grape berries are synthesised mainly before vraison, and very little attention is paid to the evolution of proanthocyanidins (PAs) in grapes from vraison to harvest. The present study focused on the changes of flavan-3-ols with different degrees of polymerisation in grape skins and the difference in proanthocyandin composition of 'Shiraz', 'Cabernet Sauvignon' and 'Marselan' grapes (Vitis vinifera L.). The results show that the content of flavan-3-ols, the percentage of prodelphinidins (%P) and mean degree polymerisation (mDP) found in 'Cabernet Sauvignon' berry skins at post-vraison were higher than those in 'Shiraz' and 'Marselan' skins. Only monomeric, dimeric, trimeric and polymeric flavan-3-ols were detected in the three grape cultivars. Polymers with more than tenfold flavan-3-ol units accounted for a relatively high proportion in grape berry skins, and the content in the three cultivars declined continuously during ripening. Principal component analysis showed that proanthocyanidin content, composition and mDP at grape harvest stage depended strongly on grape cultivar. This study provides some useful information for understanding the accumulation of PAs during berry maturation and this information can be used to improve wine quality.