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 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 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. [Copyright &y& Elsevier]