Quality Evaluation of Custard Produced from Blends of Sweet Potato and Corn Starch Enriched with Defatted Soybean

Abstract

Custard is a thick, rich, creamy sweet or savory dessert, made mixtures of eggs or egg yolks, milk or cream and commonly consumed in most part of Africa especially Nigeria. This research was carried out to determine the physicochemical properties and sensory characteristics of custard produced from the blends of sweet potato and corn starch enriched with defatted soybean flour. The sweet potato was peeled, washed and diced into small cubes to aid milling while the maize grains were cleaned and soaked in water for 24 hours, and they were separately milled and filtered. The filtrates were allowed to settle for four hours, the starches were obtained and dried at 70°C and 60°C for 8 hours and 5 hours respectively. The soybean was cleaned, soaked, boiled, toasted, dehulled, milled and defatted in petroleum ether. Ten custard samples were then formulated using sweet potato starch, corn starch and defatted soybean flour respectively in the following ratios: 100:0:0; 80:10:10; 70:20:10; 60:30:10; 50:40:10; 40:50:10; 30:60:10; 20:70:10; 10:80:10; 0:100:0. The custard formulations were evaluated for their physicochemical and sensory characteristics, using commercial custard (Checkers custard) as control. The result of the proximate composition showed that moisture, ash, crude fibre, crude protein and carbohydrate content in % ranged from 5.40-18.08, 0.70-3.07, 1.16-6.52, 0.82-5.23, 1.31-9.91 and 68.87-85.25, respectively. The functional properties also showed that least gelation concentration (%), bulk density (g/cm), swelling power and gelatinization temperature (oC) ranged from 4.00-10.00; 0.59-0.83; 6.37-8.02 and 69.2-80.1, respectively. The result showed that the swelling power differed significantly (p<0.05) from each other and some of the samples differed significantly in bulk density, least gelation and gelatinization temperature, respectively. Sensory evaluation carried out on different samples of the custard formulation showed that the control sample (Checkers custard) had the highest score of overall acceptability. The 100% corn starch and 100% sweet potato starch were accepted by the consumers as an alternative to the commercial custard product. The enrichment of custard with soybean contributed to an increase in the nutritional value of the custard.