Chemical Composition Studies on Winged Bean ( Psophocarpus tetragonolobus ) Tubers

To add data to the very limited information on winged bean tubers, samples from 26 varieties were analyzed for proximate analysis, tannin, trypsin inhibitor activity (TIA) and nonprotein nitrogen (NPN). The averages obtained were: crude fat, 0.96%, ash, 2.94%; acid detergent fiber, 16.56%; crude protein, 16.4%; carbohydrate, 57.72%; tannin, 5.32 mg/g tubers; trypsin inhibitor, 1033 TIU/g tubers. NPN constituted only a small percentage (16.2%) of the total nitrogen indicating that most of the nitrogen is protein. A significant proportion of NPN (76%) was ninhydrin positive, indicating free amino adds, peptides and possibly other amines. Tannin concentration was higher than those present in seeds. The presence of TIA necessitates heat processing before consumption.