The analysis of cider phenolics

Four classes of phenolic compounds may be distinguished in ciders: 1. Phenolic acids; 2. Phloretin derivatives; 3. Catechins; 4. Procyanidins. Only the procyanidins can be classed as true tannins and only they make any contribution to the bitterness and astringency of the product. Traditional methods of tannin analysis, however, fail to estimate the procyanidins as a separate group from the other phenolics. It is now possible to isolate the procyanidin fraction from bittersweet ciders by adsorption onto Sephadex LH-20 and then to separate the individual procyanidins by counter-current distribution between ethyl acetate and water. In this way sufficient material may be obtained to allow structural studies, and we can now show that ciders contain a range of procyanidin polymers probably up to heptameric, based mostly on epicatechin. Tasing panel work on these fractions shows that bitterness is predominantly associated with oligomeric procyanidins and astringency with polymeric procyanidins. Analytical chromatography on Sephadex LH-20 in a water-methanol gradient also shows, for instance, the selective loss of up to 20% of organoleptically significant procyanidins during gelatin fining, and the useful gain in procyanidins which can occur with DDS diffuser extraction. These results are important because a certain amount of bitterness and astringency is considered desirable in blended English ciders, but the true bittersweet apples are in very short supply.