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 (T-g), 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. T-g 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 T-g s in extrudates. Young's modulus showed water acts as anti plasticizer at low aw, while shows plasticizing effect at high a(w). A stability map can explain the brittle-ductile transition occurred while it was below T-g.