Effects of acid-hydrolysis and hydroxypropylation on functional properties of sago starch

• Dual modification of sago starch by partial acid hydrolysis and propylene oxide hydroxypropylation.
• Dual modification has synergistic effects on the physicochemical properties of starch.
• Modified sago starch is soluble at concentration of up to 25% in cold water.
• Dually modified sago starch has no retrogradation.

In this study, sago starch was hydrolyzed by 0.14 M HCl for 6, 12, 18, and 24 h, and then modified by propylene oxide at a concentration of 0–30% (v/w). The effects of hydrolysis and etherification on molecular weight distribution, physicochemical, rheological, and thermal properties of dually modified starch were estimated. Acid hydrolysis of starch decreased the molecular weight of starch especially amylopectin, but hydroxypropylation had no effect on the molecular weight distribution. The degree of Molar substitution (DS) of hydroxypropylated starch after acid hydrolysis ranged from 0.007 to 0.15. Dually modified starch with a DS higher than 0.1 was completely soluble in cold water at up to 25% concentration of the starch. This study shows that hydroxypropylation and hydrolysis have synergistic effects unlike individual modifications. Dually modified sago starch can be applied to dip-molding for food and pharmaceutical processing because of its high solubility and low tendency for retrogradation.