Analysis of proanthocyanidins in coffee pulp

Data are presented for the condensed tannins content of pulp prepared immediately from die cherries of three cultivars of freshly harvested coffee beans, and for the pulp after drying. The data have been interpreted with reference to purified quebracho profisetinidins (3.13–6.17% on a dry basis (db)) and to the E% values of the anthocyanin pigments formed by oxidative depolymerisation (0.60–1.19% db). Pulp from a yellow-fruited cultivar was significantly richer (P < 0.001) than pulp from the associated red-fruited cultivar. In contrast to previous reports the presence has been established of condensed tannin in the pulp at the time the cherry was harvested although an increase was observed on subsequent drying. Prodelphinidins could not be detected, but the presence of procyanidins was confirmed. Analysis of procyanidin dimer-rich and procyanidin oligomer-rich fractions suggested that while dimers dominate in undried pulp, dimers may be converted to oligomers during drying. Measurements of haemoglobin precipitation (relative astringency) were generally consistent with increased tannin content/polymerisation after drying but little interaction with methylene blue was detectable in any sample.