The effects of physical properties of common bean (Phaseolus vulgaris L.) varieties on soaking and cooking time

Abstract

Cookability of common bean is constrained by hardness which results to extend cooking times, low widespread consumption, and high cost of cooking fuel, the consequence of this is malnutrition due to nutritional deficiencies and food insecurity. A study was conducted in the seed Laboratory of Kenya Agricultural and Livestock Research Institute (KALRO)-Katumani to investigate the effects of physical properties of eleven bean varieties (GLPX92, KATX69, EMBEAN118, WAIRIMU, EMBEAN14, GLP2, KATX56, KATB9, KATRAM, KATB1 and KATSW-13) in relation to soaking and cooking time in a complete randomized design replicated three times. Bean samples for long and short rains 2016 that were stored for 5 and 8months respectively were evaluated for the effect of water imbibition in relation to cooking time, effect of water imbibition in relation to grain hardness and differences in physical properties and their effects on cooking time. After retrieval from the storage, the samples were size graded manually, weighed and randomly picked 50 grains from each variety which were divided into two groups of 25 and 6 grains for use in cooking and grain hardness respectively. These were weighed and rinsed with distilled water before soaking at varying soaking times of 0, 3, 6, 12 and 24 hours. All the collected data was subjected to analysis of variance (ANOVA) using SAS (version 9.1.3) to detect differences between treatments. Mean separation for significant treatments were carried out using Fisher’s protected least significant difference test at p< 0.05 level and correlation between physical properties (length, width and thickness), hardness, water imbibition and cooking time were determined. The results showed that, the overall water imbibition and cooking time for KATB1 and KATSW-13 imbibed the highest amount of water and also cooked significantly faster than other varieties in both the seasons’ whileKATX69andGLPX92took significantly longest time to cook in both the seasons respectively. In terms of hardness, in short rains, KATX69 had the hardest seed coat whileKATSW-13 had the softest. In long rains KATRAM was the hardest while EMBEAN118was softest. Physical properties (length, width and thickness) were significantly higher for short rains than for long rains 2016. In short rains, EMBEAN118 and KATSW-13 had significantly (p<0.05) recorded both the highest length and lowest thickness respectively. The width didn’t have significant difference among the varieties. For long rains, GLP2 and KATRAM had the highest and lowest lengthrespectively.The width of KATX56 was highest and EMBEAN14 the lowest. KATSW-13 had the highest thickness while KATRAM had lowest. The physical properties of beans affected the cooking time significantly in both the seasons which could be linked to the permeability of the seed coat that influences water imbibition in individual beans. The study recommends breeding of bean varieties with less permeable seed coat which could aid in faster cooking as this would save cost on fuel and time.