RELATIONSHIP BETWEEN THEORETICAL AND EXPERIMENTALLY DETECTED TANNIN CONTENT OF COMMON BEANS (PHASEOLUS-VULGARIS L)

The present study was undertaken to determine the degree of any relati onship between the theoretical and the experimentally determined tanni n content in common beans. With this objective, theoretical tannin con tent was calculated as a function of seed coat tannin content and seed coat percentage weight in 19 varieties of common beans, grown in two localities of the Mexican highlands. The percentage of undetected tann ins was calculated by the difference for all cultivars. The theoretica l tannin content was correlated with the tannins detected experimental ly in whole bean flour. The undetectable tannins ranged from 9.9 to 66 .4% for varieties grown in Aguascalientes, and from 4.1 to 69.7% for c ultivars harvested in Durango. A significant positive correlation was observed between the values of the theoretical tannin content and tann ins detected experimentally in cultivars from Aguascalientes (r=0.81, P<0.01) and Durango (r=0.72, P<0.01). Nevertheless, there were many ex amples that showed the real content of tannins to have been underestim ated. In accordance with this study, it is propose that, in order to o btain the real content of tannins of beans, these compounds should be determined in the seed coat flour. (C) 1996 Elsevier Science Ltd.