THE HARD TO COOK DEFECT IN COMMON BEANS: UNDERSTANDING THE EFFECT OF S TOR AGE CONDITIONS ON PHYSICAL, COOKING AND NUTRITIONAL PROPERTIES

Abstract

Common beans are highly nutritious and widely consumed in Kenya. Storage of common beans under adverseconditions of high temperature (≥25°C) and high humidity (≥ 65%) renders them susceptible to the hard-tocook (HTC) defect. This results in increased cooking time, fuel and water use. This has a negative effect onacceptability  and  utilization of  beans.  The  objective  of this  study was  to  determine  effects  of storagetemperature and relative  humidity on development of the HTC  defect  in common beans and subsequentphysical and  nutritional quality changes. Rose  coco  and Red kidney  bean  varieties  were  obtained fromKenya  Agricultural  Research Institute (K ARI) -  Thika. The beans  were subjected to combination of varying temperature (35˚ C and 45˚ C) and relative humidity (75% and85% RH). Beans from each treatment condition were sampled at an interval of zero, two, four and six months followed by analysis of  physical, cooking and nutritional properties.   There w a s  a significant i n c r ea s e i n conductivity and  leached  solutes.  Significantdecrease  was  observed  in  hydration  and  swelling coefficients  of beans  under  each  storage  condition. Characteristic  dimensions  and  one  hundred seed weight were  not significantly different among the  variousstorage conditions. Based on the results of this study, it was concluded that adverse storage conditions oftemperature (35˚ C and 45˚ C) and relative humidity (75% and85% RH) cause development of the HTC defectwhich in turn affects physical properties and cooking quality of common beans.

Key words: HTC defect, storage conditions, physical properties, cooking quality