Composition and effect of soaking on starch digestibility of Phaseolus vulgaris (L.) cv. 'Mayocoba'

Common beans from Mayocoba variety were soaked in different solutions, cooked, stored and evaluated for cooking time, chemical composition and in vitro starch digestibility. Soaking decreased cooking time; the lowest value (149 min) was obtained when a sodium chloride (1%) and sodium bicarbonate (0.75%) mixture was used. Total starch content in samples soaked in water, sodium chloride or sodium bicarbonate increased in relation to the non-soaked sample, a pattern that may be associated with lixiviation of other bean components, which leads to increased TS content. Soaking also affected available starch (AS) levels, because beans soaked in sodium bicarbonate solution exhibited the lowest AS; on the contrary, beans soaked in water and sodium chloride showed higher AS contents than non-soaked beans. In agreement with AS content, beans soaked in bicarbonate solution presented the highest resistant starch values. Soaking in diverse solutions did not affect the hydrolysis index and consequently the predicted glycaemic index(pGI). pGIs of Mayocoba beans reiterate the well-known beneficial 'slow digestion' features of starch in pulses.