Influences of temperature-cycled storage on retrogradation and in vitro digestibility of waxy maize starch gel

Abstract

Waxy maize starch gels prepared from 40% starch solids were retrograded, either isothermally at 4 °C or at cycles of 4 °C and 30 °C (2 days each), for 16 days. The properties of retrograded starch gels were determined by differential scanning calorimetry (DSC), X-ray diffraction patterns, textural properties, and in vitro digestibility. The starch crystals formed in the gel stored under the 4/30 °C cycled conditions melted at a higher onset temperature with a narrower endothermic peak and a lower enthalpy than those formed under constant temperature storage at 4 °C. No differences between the two storage conditions were observed in the X-ray diffraction patterns of retrograded starch. The glass transition temperature ( T g ′ ) increased and the ice melting enthalpy decreased throughout the retrogradation process regardless of the temperature cycle. The starch gel stored under the cycled temperature conditions exhibited slightly lower T g ′ and greater ice melting enthalpy than those stored under the constant 4 °C. The starch gel retrograded at the cycled temperature conditions remained softer than those stored under constant temperature with similar springiness. The cycled temperature storage induced a greater amount of resistant starch and reduced the in vitro glycemic index more effectively than the isothermal storage condition.