EFFECTS OF SOAKING ON THE COOKING TIME OF DIFFERENT COMMON BEAN (PHASEOLUS VULGARIS L.) VARIETIES GROWN IN KENYA

Abstract

Production of common beans (Phaseolus vulgaris L.) in Kenya is characterized by a large variety of beans of different cooking properties. Despite the well-known nutritional and functional benefits of bean consumption, the hard-to-cook (HTC) defect continues to be a major hindrance to the widespread consumption of beans. Pre-cooking treatments can play a major role in reducing the cooking times of the beans and thus increase the acceptability and consumption of beans. This requires innovative scientific and technological approaches for altering the physico-chemical properties of the beans to meet certain functionalities. One such approach is soaking of the beans prior to cooking. The aim of this study was to provide quantitative information on the effect of soaking in different brine solutions on the cooking quality of different bean varieties grown in Kenya. During this study, four common dry bean varieties were soaked in deionised water at varying temperatures (20-50oC) to determine the optimum soaking temperature. They were also soaked in solutions containing monovalent and divalent salts, chelating agents and phytic acid. The influence of soaking solution pH (4-8.5) on the cooking time was also determined. Soaking at high temperatures increased the hydration rate and decreased soaking time to achieve equilibrium moisture content in the beans. Soaking in CaCl2 solution and low pH solutions increased the cooking time of the beans while soaking in deionised water and high pH solutions reduced the cooking time. These results indicate that soaking has significant effects on the cooking time.