Abstract

Mucuna bean (Mucuna pruriens) is an indigenous legume promoted in Kenya as a green manure cover crop. It contains high protein but it is under - utilized due to the presence of 3, 4-dihydroxy-L-phenylalanine (L-Dopa) and other anti nutritional compounds. To improve its nutritional potential as a protein source, mucuna bean was processed and evaluated for nutritional composition. Effects of processing at different pH, temperature and particle size, autoclaving, germination and fermentation on the contents of anti-nutritional compounds and crude protein were investigated. Raw beans contained high crude protein (27.9 g/100^-1). Contents of ether extract; crude fibre and ash were 3.7, 7.9 and 3.5 g/100^-1, respectively. Mineral content was comparable to that of common pulses. Raw whole mucuna bean contained high L-Dopa (7.0 g/100^-1) content. Other anti-nutritional compounds included total phenols 7.1 g/100^-1, trypsin inhibitor activity (TIA) 5.1 TIU and phytates 0.9 g/100^-1. All processing techniques, except roasting, reduced levels of L-dopa by > 95% while less than 15% of protein was lost. Soaking dehulled bean in acidic medium (pH 3.2) at 60°C for 48 h reduced L-Dopa content to the recommended safe level of 0.1%. Processing mucuna bean increased its nutritional value and potential to improve food security.

Key words: Mucuna bean, anti-nutritional compounds, L-Dopa, processing methods.