EFFECT OF HOME-COOKING TREATMENTS IN THE PREPARATION OF PINTO BEANS (PHASEOLUS-VULGARIS L) ON THE TANNIN CONTENT AND NUTRITIVE-VALUE OF PROTEINS

A 3(2) factor design was carried out in order to investigate the different home-cooking treatments applied in the preparation of pinto beans (Phaseolus vulgaris L.) on the nutritive value of their protein. The factors studied were previous soaking, type of cooking and addition of cooking broth. Biological evaluation of the protein was performed, and the protein efficiency ratio (PER) and apparent digestibility of the protein (DAP) values were obtained. The tannin content was measured in hulls, cotyledons and in the cooking broths of each experimental treatment. The most significant effect of the PER value was the type of cooking (P < 0.0001), followed by the addition of cooking broth (P < 0.05) as well as a significant interaction between cooking method and addition of broth (P < 0.025). Soaking did not have significant effects per se or through its interactions in relation to PER. The highest values for PER and DAP were obtained with the boiling treatment without broth. The detrimental effect of the cooking broth can be explained by its tannin content (108.5 - 272.25 mg Eq. catechin/100g).