Changes in Amino Acids, Anti-Nutrients and Functional Properties of African Yam Bean Flour Caused by Variation in Steeping Time Prior to Autoclaving

Background and Aim: Legume seeds are usually steeped in water or bicarbonate solution before further processing and this has some effect on the constituents and functional properties of the flour. The present study was to evaluate the effect of steeping time in 0.50% solution of unripe plantain peel ash prior to autoclaving on the amino acids, anti-nutrients and functional properties of African yam bean flour.

Study Design: Analysis of variance (ANOVA) was carried out.

Place and Duration: Department of Food Science and Technology, University of Uyo, Akwa Ibom State, Nigeria, from November 2016 to May 2017.

Methodology: African yam bean seeds were sorted, washed and divided into four portions of 500g each. Portion I was not steeped and served as control sample while portions 2, 3 and 4 were steeped in 0.50% solution of unripe plantain peel ash (1:5w/v) at ambient temperature (27±2ºC) for 24, 48 and 72h respectively. Both the unsteeped and steeped portions were separately autoclaved, dehulled, oven dried, milled and sieved to obtain the flours used for analysis.

Results: The result revealed that all the parameters varied with steeping time. The total amino acids and total essential amino acids increased from 75.52g/100g and 30.07g/100g in the flour from unsteeped seeds to 80.29g/100g and 32.87g/100g respectively in the flour from the seeds that were steeped for 72h. Phytate, tannin, trypsin inhibitor, raffinose, stachyose, bulk density, water absorption capacity and swelling index decreased while oil absorption and foaming capacities increased with steeping time. Percentage reduction of phytate, tannin, trypsin inhibitor, raffinose and stachyose after 72h steeping were 80, 86, 98, 97 and 94%, respectively.

Conclusion: The treatment caused significant (p<0.05) reduction in anti-nutrients and flatulence causing factors and enhanced amino acid profile of the flour.