Content of antinutrients and in vitro protein digestibility of the African yambean, pigeon and cowpea.

Abstract

The protein, trypsin inhibitor (TI), tannin, phytate, phytic acid phosphorus and in vitro protein digestibility (IVPD) of cultivars of the African yambean (Sphenostylis stenocarpa) - AYB, pigeon pea (Cajanus cajan) - PP and cowpea (Vigna unguiculata) - CP were determined. The protein content of CP (24-28.0%) was higher than those of PP (21-22.5%) and AYB (21-22.5%). The cream and speckled AYB contained more TI (30.9 and 25.3 mg/g) than PP (7.5-14.1 mg/g) and CP (9.8-20.5 mg/g). Apart from the white CP cultivar, they contained more tannin (1.24-1.42 mg/g) than PP (0.14-0.97 mg/g) and AYB (0.71-1.17 mg/g). Phytate was lowest in the AYB (6.30-7.49 mg/g) than PP (8.31-11.31 mg/g) and CP (8.40-9.92 mg/g). Phytic acid contributed 67-74% of the phosphorous in the AYB, 66-75% in PP and 54-59% in CP. The IVPD of the AYB (73.3 + or - 0.7%) was significantly lower (p <0.05) than those of PP (76.34 + or - 0.2%) and CP (77.8 + or - 0.4%). There was a significant negative correlation between TI and IVPD (r = -0.63, p<0.05). There was no significant correlation between IVPD and phytate and tannin contents. There was a positive correlation between protein content and IVPD (r = 0.69**) for the legumes under study. These legumes may pose no serious problems to populations consuming them especially when heat treatment is applied before consumption.