Interaction between grape-derived proanthocyanidins and cell wall material. 1. Effect on proanthocyanidin composition and molecular mass.

Insoluble cell wall material was prepared from the skin and flesh of commercially ripe Vitis vinifera L. cv. Shiraz berries and then combined in suspension with preveraison skin and seed proanthocyanidin containing solutions. Analysis of proanthocyanidins before and after fining with cell wall material by phloroglucinolysis provided information on recovery by mass, subunit composition, and mean degree of polymerization, whereas proanthocyanidin molecular mass distribution was determined by gel permeation chromatography. Cell wall material from flesh showed the highest affinity for proanthocyanidin, binding up to 47% and 57% w/w of total seed and skin proanthocyanidin respectively. Comparison of the molecular mass distribution of skin or seed proanthocyanidin before and after fining indicated that affinity of cell walls for proanthocyanidin increased with increasing proanthocyanidin molecular mass. Initial results of subunit composition of skin and seed proanthocyanidin mixtures following fining with cell wall material showed that the % galloylation decreased, suggesting a preference for seed-derived proanthocyanidins. Subsequent experiments suggest that fining with insoluble cell wall material is size-based and does not have a specific affinity for seed-derived proanthocyanidins.