Interaction of grape seed procyanidins with various proteins in relation to wine fining

Interactions of grape (Vitis vinifera L) seed procyanidin dimers and trimers, galloylated or not, with various proteins poly-L-prolines, gelatins, casein, dried blood and grape arabinogalactan-protein) were studied in wine-like model solutions. Except for casein, protein-procyanidin complexes were produced within the first 8 h of contact. All poly-L-prolines presented very high affinity towards grape seed procyanidins. In general, the extent of procyanidin-protein interaction increased with the degree of procyanidin polymerisation and the rate of galloylation, and also with protein concentration. When various protein fining treatments were applied to a young red wine, dimeric and trimeric procyanidin levels were not affected, although total phenolic levels were reduced.