Effect of Fermentation on the Functional and Chemical Properties of African Star Apple Seed Flour

Abstract

African star apple seeds were fermented and processed into flour at different periods of 24, 48 and 72 h respectively with an unfermented African star apple seed flour as the control. The functional properties, pasting properties, antioxidant activity, antinutritional and proximate composition of the flours were determined. The functional properties of the flour samples showed that bulk density ranged from 0.56g/ml-074 g/ml. There was a significant decrease in bulk density with increase in fermentation time. There was also a significant increase in water absorption capacity and oil absorption capacity with increase in fermentation time which ranged from 180-237% and 130-170% respectively. However, swelling index and dispersibility ranged from 2.00-3.00% and 30-43.33% respectively. The pasting properties of African star apple seed flour ranged between 29.75-111.42 RVU for peak viscosity, 23.83-83.33 RVU for trough viscosity, 42.00-109.58 RVU for final viscosity which shows a significant increase with increasing fermentation time. Antioxidant activity which includes DPPH, FRAP, ABTS ranged from 19.75– 40.61%, 0.37– 0.40 mgFeSO4/g, 30.07 - 40.51mgTE/g respectively while Phytochemical properties revealed that total tannin content were negligible, total flavonoids content, total phenolic content ranged from 0.04– 0.11mgCE/g and 0.05–0.18 mg CE/g respectively. The proximate composition showed reduction in ash and fibre contents while there were increase in protein and fat contents with fermentation periods. Fermentation of African star apple for 48 h showed increase in antioxidant and protein contents while fermentation for 72 h improved the functional and pasting properties of the seed flour.