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).
