Freeze-thaw stability, glass transition, and retrogradation of high hydrostatic pressure-assisted hydroxypropylated corn starch

Abstract

Effects of high hydrostatic pressure (HHP) and the propylene oxide (PO) concentration on the freeze-thaw stability, glass transition temperature (Tg′), and retrogradation degree of HHP-assisted hydroxypropylated corn starch were investigated. HHP-assisted hydroxypropylated corn starches were prepared using propylene oxide (4, 8, and 12%, v/w) at 25°C for 15 min under HHP (100, 200, 300, and 400 MPa). The freeze-thaw stability, Tg′, ice melting enthalpy (H i ), and retrogradation degree of HHP-assisted hydroxypropylated corn starches showed patterns different from native corn starch. In general, higher pressures and PO levels lowered Tg′ and H i values, and the retrogradation degree. The highest freeze-thaw stability was observed in HHP-assisted hydroxypropylated corn starch prepared using 12% PO at 400 MPa for 15 min. Retrogradation kinetics of hydroxypropylated corn starch gels observed from the glass transition temperature, ice melting enthalpy, and retrogradation degree revealed that recrystallization occurred with instantaneous nucleation, followed by rod-like growth of crystals.