Effect of Processing Methods on the Proximate and Energy Composition of Lablab Purpureus (Rongai) Beans

Abstract

Four methods of processing were assessed to investigate the effect of processing methods on the digestibility, proximate and energy composition of Lablab purpureus (Rongai) beans. The processing methods were boiling (in water), fermentation, toasting and fermentation plus toasting. Some of The beans were boiled for 0, 10, 20, 30, 40, 50 or 60 minutes and sundried for three days before proximate analysis. For the beans processed by fermentation, they were soaked in water for 0, 24, 48 and 72 hours respectively and sundried for three days before analysis. Samples were toasted for 0, 10, 20, 30, 40 and 50 minutes respectively using a frying pan over an open wood fire, with constant stirring to prevent charring. The last treatment involved the beans first being fermented for 0, 24, 48 and 72 hours, dried in the sun for three days, before being toasted for 10 minutes. The beans were then milled. A representative sample of the milled lablab beans from each of the processing method along with a raw sample of the beans were taken to the laboratory for proximate analysis. Estimates of gross, digestible and metabolizable  energy values beans was done through standard mathematical formulae using the values of their proximate composition. Results obtained indicated significant differences in proximate and energy composition due to processing method.

Keywords: Processing, cooking, fermentation, toasting, lablab beans, energy, proximate.