Identification of complex glass transition phenomena by DSC in expanded cereal-based food extrudates: Impact of plasticization by water and sucrose

The physical state and mechanical properties of extruded cereal based products were studied as a function of sucrose content and relative humidity (RH) to evaluate how the presence of sucrose affects glass transition temperature (Tg), sorption isotherm, and texture parameters. Extrudates were prepared with different sucrose content (0-20 %wt). Sorption isotherm showed the water content of extrudates decreased when product contains high sucrose at low aw range and the inverse effect was observed at high aw. Tg s were determined using differential scanning calorimetry (DSC) and two transitions were detected on the heat flow first derivative curve. Addition of sucrose or water decreased both Tg s in extrudates. Young's modulus showed water acts as anti-plasticizer at low aw, while shows plasticizing effect at high aw. A stability map can explain the brittle-ductile transition occurred while it was below Tg.