Ultra high pressure (UHP)-assisted hydroxypropylation of corn starch

Reactivity and property of corn starches hydroxypropylated under ultra high pressure were investigated as a function of either pressure levels or pressure holding times. Corn starch was derivatized with propylene oxide (PO) either at 0.1–400 MPa for 15 min or at 400 MPa for 5–25 min, and assessed with respect to molar substitution (MS), X-ray diffraction pattern, solubility, swelling power, gelatinization, and pasting behavior. While an increase in pressure level enhanced MS values of UHP-assisted PO starch derivatives, starch reactivity was less influenced by pressure holding time. UHP-assisted PO reaction reduced reaction time to the greatest extents compared to long reaction time in conventional PO reaction. UHP-assisted PO starch derivatives revealed similar solubilities/swelling powers, and gelatinization properties, regardless of pressure levels. Higher gelatinization temperature was observed for UHP-assisted PO starch derivatives and their respective controls relative to native starch, implying that UHP-assisted reaction might involve starch annealing.