Functional properties of modified starch from Pachyrhizus erosus (yam bean) tuber

Abstract

In this study, chemical characteristics of starch isolated from Pachyrhizus erosus (yam bean) tuber were determined. The starch was then modified through pregelatinization, cross-linked phosphorylation and acetylated starch esterification and characterized in terms of their physical properties. The yield of Pachyrhizus erosus starch was 2.26% and the starch contained 83.99% total starch, 84.94% carbohydrate, 5.11 % protein, 0.0063% lipid, 3.04% moisture content, 6.83% ash, 14.39% amylose and 85.61 % _ amylopectin. Pregelatinization resulted in a better swelling power (10.90 gig) compared to acetylated esterified starch (7.98 gig) and cross-linked phosphorylated (7.23 gig). Better solubility also present in pregelatinizated starch (12.98%) follow with acetylated esterified starch (11.35%) and cross-linked phosphorylated starch (11.28%). Meanwhile, acetylated esterified starch gave better water binding capacity (9.20 gig) relative to pregelatinizated (8.27 gig) and cross-linked phosphorylated starch (7.35 glg).It was also found that the effect of each factor on swelling power, solubility and water holding capacity was significantly (p < 0.05) depended on types of starch at different temperature and vice versa. Acetylated starch ( 17. 72%) demonstrated the best stability in freeze-thaw cycle followed by cross-linked phosphorylated starch (23.65%), pregelatinized starch (33.21%). Light microscope was using to observe granule characteristic and temperature onset until complete gelatinization. Acetylated starch gave higher gelatinization temperature (91 C) and cross­ linked phosphorylated starch (78 ° C) then pregelatinizated starch (84 ° C), native starch (88 ° ° C).