Untitled research work

The retrogradation behaviors of sweet potato, potato, corn and wheat starches were studied comparatively in terms of the paste concentration. Starch pastes of 2.5, 5, 10, 20, and 30% concentration were prepared by heating the starch-water suspensions at 100°C for 15 min and the resultant pastes were cooled at 0°C for 1 hour. The progress of retrogradation was estimated by the degree of gelatinization which was measured by the glucoamylase and iodine binding methods. A rapid increase in retrogradation with increase of paste concentration was noted in the pastes of sweet potato and potato starch. This concentration dependent retrogradation was more evident in the paste of potato starch than that of sweet potato. Sweet potato starch showed the least retrogradation among the starches tested. The potato starch paste retrograded at a slower rate than that of corn and wheat starches below 10% concentration but retrograded at as rapid a rate as that of the cereal starches above 20% concentration. Corn and wheat starches showed very similar retrogradation behavior with paste concentration but differed from potato and sweet potato starch. The retrogradation rates of these cereal starches were increased with an increase of paste concentration from 0 to 5% but the rates were nearly constant above 5%.