CHEMICAL-COMPOSITION AND STRUCTURE OF 2 MEXICAN BEAN (PHASEOLUS-VULGARIS L) CULTIVARS IN RELATION TO COOKING TIME

The influence of seed structure, chemical composition and hydration rate on the cooking time for consumption (CTC) of two Mexican cultivars of beans [Ojo de Cabra (OC) and Michigan (MI)] was studied. The cultivars showed different cooking time and rate of hydration but the same water uptake after imbibition time. Anatomical studies showed that OC, with the higher CTC, has a lower rate of hydration, thicker seed coat, higher percentage of seeds with obliterated mycropile and reduced surface area of the seed. Thus, the structural characteristics of the seed influence hydration rate but not hydration capacity. Also, the presence of tannins in the different structures was detected by histochemical tests. Due to the differential effect of soaking on the bean texture, the results suggest interaction between tannins and cytoplasmic macromolecules which could result in a higher thermal stability of these components.