Quantifying the Effects of Postharvest Storage and Soaking Pretreatments on the Cooking Quality of Common Beans (Phaseolus vulgaris )

Abstract

Cooking quality of common beans greatly influences acceptability. The objective of this study was to quantify the effect of bean type, storage time, temperature and relative humidity (RH) on the cooking time of four bean types grown in Kenya. Beans were stored under different temperature (25, 35 and 45C) and RH (75 and 83%). After sampling, they were pre-soaked or not and cooked to generate cooking curves which were subjected to nonlinear regression. Significance of the different variables was evaluated using mixed model regression. Higher storage temperatures (35 and 45C), higher RH (83%) and extended time significantly increased lag phase and cooking time. Soaking pretreatments reduced cooking time. Canadian wonder and Pinto beans took long thus hard-to-cook while Rose coco and Red haricot took short cooking time, thus, easy-to-cook. This work demonstrated the critical nature of bean type, storage and pretreatment conditions in influencing bean cooking quality. Practical Applications The hard-to-cook (HTC) problem in common beans is one of the main problems leading to low consumption of beans. This manuscript provides information on the easy to cook and HTC bean varieties grown in Kenya. The roles of storage temperature and relative humidity on predisposing beans to the HTC problem is discussed including the optimal storage conditions. Finally, the effect of pre-treatment conditions and cooking on overall cooking time is highlighted. Soaking in distilled water and Na2CO3 significantly reduced the cooking time of the beans. It is hoped that this information can be translated to practical guidelines for bean breeders, stockists, processors and consumers.