Quality Attributes of Custard Prepared from Selected Varieties of Sweet Potato Starch Enriched with Soy Protein Isolate

Abstract

The study investigated the effect of soy protein isolate (SPI) addition on the quality attributes of custard from selected varieties of sweetpotato starch (SPS). Starch was prepared from orange-fleshed sweetpotato (OFSPS) and yellow-fleshed sweetpotato (YFSPS). Simplex lattice design was employed to obtain the various combinations of SPS and SPI. Proximate composition, instrumental colour, functional and pasting properties of the sweetpotato starch and the blends were determined. The sensory attributes of the optimized custard samples with the commercial custard were determined using t-test. The protein and ash contents increased while the fat and carbohydrate contents decreased as the inclusion level of SPI increased in the blends. The addition of SPI significantly decreased (p<0.05) the dispersibility, packed bulk density; peak, trough, breakdown, final and setback viscosities but increased the least gelation concentration, water absorption capacity and swelling power of the blends. There was significant (p< 0.05) difference in the sensory attributes of cooked custard prepared from the optimized blends and the control sample. In conclusion, blending 80% OFSPS with 20% SPI; and 75% YSPS with 25% SPI produced acceptable custard.