Physicochemical and Functional Properties of Yellow Yam (Dioscorea Cayenensis) Starches and Sensory Quality of Its Custard

Abstract

Background: Corn has been the major source of starch used in the production of custard. Therefore there is need to harness other sources of starch for the production of custard.
Objective: This study evaluated some physicochemical and functional properties of starches extracted from two varieties (TDC2790 and TDC2812) of yellow yam (Dioscorea cayenensis) and cornstarch and the sensory attributes of the custard made from the starches.
Methods: Weights of the yam were measured and starch extraction was carried using standard laboratory procedures. Starch yield was calculated, proximate composition, amylose and amylopectin contents, carotenoid, colour and functional properties were determined.
Results: Percentage starch yield from TDC2790 and TDC2812 were 18.97% and 12.50% respectively. Amylose and amylopectin content ranged from 16.10-31.46% and 68.54-83.90%, respectively in the starches, the general low content of amylose in the starches. Carotenoid content ranged from 3.15-6.93μg/g, large variation in total carotenoid content observed among the starches was a reflection of the wide spectrum of the colour of flesh of the yellow yam tubers.
Conclusion: Carotenoid content, functional properties of the starches and sensory attributes of the custard differ significantly (p<0.05). The values for turbidity of starch paste increased progressively during storage and this can be attributed to the interaction between leached amylose and amylopectin chains that led to development of function zones, which reflect or scatter a significant amount of light.