Physical and Cooking Properties of Two Varieties of Bio-Fortified Common Beans (Phaseolus Vulgaris. L) Grown in DR Congo

Abstract

Common bean (Phaseolus vulgaris L.) is the most widely grown edible legume species in DR Congo but nevertheless, different varieties vary with respect to their physical, chemical aspects and cooking properties which affect the consumer acceptability. This study evaluated the physical properties and cooking time of two varieties of bio-fortified common beans (HM21_7 and Namulenga), destined for both direct consumption and processing. The parameters assessed included the dimensions, the soaking characteristics, the density characteristics, Colour and the Hardness after cooking. The beans were soaked in distilled water and in 0.025N Na₂CO₃ solution for 16h then subjected to different test as mention above. The data collected were subjected to Analysis of Variance (ANOVA) using Statistix version 8.1 software. Treatment means were separated using LSD at 0.05 probability level.  HM21_7 was larger in size and 100 seeds weight with (36.27±1.33 g) compared to Namulenga (32.77±0.55 g). The sphericity was (54.4% and 58.9%), surface area was (127 mm² and 118 mm²), aspect ratio was (0.49 and 0.55) and volume was (147 mm² and 142 mm²) for both HM21_7 and Namulenga respectively. The soaking solutions had a significant effect on the hydration coefficient, swelling coefficient. Soaking the beans in Na₂CO₃ increased significantly the conductivity and the leached solutes for both the varieties. Namulenga variety had the higher bulk density (0.81 g/ml) compared to HM21_7 (0.77 g/ml). The porosity varied significantly among the two varieties. A significant different (P<0.01) was observed in the colour of the beans after soaking. Beans soaked in distilled water were lighter due to greater pigment leaching. On the other hand, beans soaked in Na₂CO₃ solution for 16 h showed darker colour. Soaking in sodium carbonate solution prior to cooking significantly reduced the hardness of the beans compared to the unsoaked beans and beans soaked in distilled water. According to the characteristics studied, the Namulenga variety is a good option for both processing and domestic use.

Keywords: Physical properties, Hardness, Bio-fortified beans.