EFFECT OF GERMINATION ON PROXIMATE COMPOSITION, MINERAL BIOAVAILABILITY AND FUNCTIONAL PROPERTIES OF AFRICAN YAM BEAN SEED FLOUR

Abstract

The effects of germination on the quality attributes of African yam bean (Sphenostylis stenocarpa) seed, an underutilized legume were investigated. The seeds were subjected to germination at 25 ºC for 24 h, 48 h, 72 h and 96 h after which they were dried, milled into flour and the effects of germination on the proximate composition, anti-nutritional contents, mineral bioavailability and the functional properties of the flour samples were determined. The protein contents of the germinated flour samples ranged between 20.3 and 21.3% with highest value recorded after 24 h of germination. The fat content, ash content and the crude fibre of the germinated flour samples ranged from 2.27- 2.67%, 3.47 -3.80 and 2.10 - 2.67%, respectively. The fat and the crude fibre decreased with the geminating period while the ash contents increased. There was a general increase in the mineral availability with increase in germination period. Calcium content increased from 48.33 to 51.67 mg/100 g; iron content from 6.23 to 6.43 mg/100 g; magnesium from 41.67 to 48.33 mg/100 g; and phosphorus from 141.67 to 146.67 mg/100 g. There were reductions in the anti-nutritional contents of the flour samples with the germinating process.  There was about 50% reduction in oxalate content; 35% reduction in phytate and 100% in trypsin inhibitor content. The germination process had effects on the swelling capacity, foam capacity and water absorption capacity of the flour samples. The bulk density ranged between 0.67 and 0.71 g/cm3; water absorption capacity from 196.67% to 178.33%; swelling capacity from 1.77-1.50%; and foaming capacity 39.43-31.57%. Germination of African yam bean seed had effects on the proximate composition, functional properties, reduction of the anti-nutritional content and increment on the bioavailability of some minerals which could help to increase the potential of this underutilized crop in food products