Effect of differential processing methods on L-Dopa and protein quality in velvet bean, an underutilized pulse

Different accessions of velvet bean were subjected to traditional and technological processing methods like soaking, germination, microwave cooking, dry heating and γ-irradiation with a view to assess the extent to which the L-Dopa gets reduced. Furthermore, the impact of certain processing methods on the levels of total protein and essential amino acid profiles was also assessed. The percentage of L-Dopa in the raw seeds ranging from 5.63 (Mundanthurai white-coloured) to 4.44 g/100 g DM (Mundanthurai black-coloured). The processes of germination (120 h) and soaking in Ca(OH)2 solution effected significant reduction in the content of L-Dopa (i.e., from 34.8% to 58.4%; and 5.6% to 54.5%, respectively). On the contrary, dry heat treatment and microwave cooking appeared to be less effective in reducing the contents of the same. While, γ-irradiation at 10 kGy seemed to be more effective in reducing the L-Dopa than at 5 kGy. Soaking in calcium hydroxide, microwave cooking and γ-irradiation had little impact on the profiles of essential amino acids except cystine (which was completely deactivated) in both the accessions of Thachenmalai. Nonetheless, in Thachenmalai (black-coloured) accession upon soaking in calcium hydroxide, the levels of valine, phenylalanine, tyrosine, isoleucine and histidine were found to be comparable with FAO/WHO (1991) requirement pattern. To sum up, of the various processing methods employed in the present study, germination and soaking in calcium hydroxide were effected greater reduction in L-Dopa content and caused minimum effect on the profiles of essential amino acids of seed proteins.