CHANGES IN TANNIC COMPOSITION OF REPRODUCTION CORK QUERCUS-SUBER THROUGHOUT INDUSTRIAL PROCESSING

Tannic composition was studied in reproduction cork samples from three different trees of Spanish Quercus suber and at different industrial processing stages. The ellagitannins, roburins A and E, grandinin, ves calagin, and castalagin, were identified and quantified by HPLC. Globa l evaluations of tannins were also carried out, using classical chemic al methods. The group of hydrolyzable tannins was the most abundant in the tannic extract in all samples; among them, castalagin was the mai n component, followed by vescalagin, grandinin, roburin E, and, to a m uch lesser extent, roburin A. The changes in tannic composition throug hout the industrial processing are mainly related to the boiling proce ss and are more pronounced in total phenol and proanthocyanidin conten ts than in individual ellagitannins content. Vescalagin and roburins A and E were selected as those variables that provided the greatest dis crimination among stages. Important differences in the ellagitannin co ntents were observed among the trees studied, all of the ellagitannins being discriminant variables in this case.