INFLUENCE OF STORAGE CONDITIONS ON DEVELOPMENT OF HARD TO COOK DEFECT IN COMMON BEANS AND THE SUBSEQUENT NUTRITIONAL CHANGES

Abstract

Common beans form one of the main sources of proteins in poor sub-Saharan Africa. However, common beansare succumbed to the Hard-to-cook (HTC) defect which is suggested to develop due to storage at temperatureshigher than 25ºC and relative humidity of more than 70%. This results in increased cooking time, fuelconsumption and water use thus lowering the rate of utilization of beans at domestic level. This study wasaimed at understanding the development and the effects of hard to cook on an easy and hard to cook beanvarieties. Samples were collected from KARI (Kenya Agricultural Research Institute), Thika. The hard (Pinto)and easy (Red Haricot) to cook beans were stored at varying temperatures (25, 35, and 45°C) and humidity (75and 85%) levels, followed by pre-treatment (soaking in deionized water, sodium carbonate and calciumchloride) and thermal treatment. The samples were assessed for physical (Seed density, seed porosity,characteristic dimension of beans, hydration coefficient, and swelling coefficient) changes. Beans stored at45ºC at 75% RH were significantly harder than those stored at 25ºC/75% and 35ºC/85% after 2 months. Thehydration coefficient and swelling coeffient decreased with increasing storage time while the geometricproperties did not change. Bean hardness, solutes and electrolytes leaching after 16hr soaking substantiallyincreased with increased temperature. It was concluded that the longer the beans are stored at highertemperatures the more they develop the hard to cook defect.