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The degree of heterogeneity in three non-expanded amylopectin–sucrose (88:12, 68:32 and 57:43) systems prepared by twin-screw extrusion was studied using FTIR microspectroscopy. The results obtained with a spatial resolution of 30 μm suggested a fluctuation in the compositions of these blends. As expected, the heterogeneous character of these blends was reflected in their thermomechanical behaviour as studied by DMTA. The thermograms of the blends containing 27–29% water (db) exhibited typically four transitions (tan δ peaks) which were assigned to a β-relaxation process, T1 (−44 to −24 °C), a glass-transition of a sucrose-rich phase, T2 (−20 to −6 °C), an ice-melting transition of the sugar-rich phase, T3 (−10 to −2 °C) and a glass-transition of an amylopectin-rich phase, T4 (3 to 22 °C) depending on the blends composition. The reduction of the water content by dehydration of these blends down to 9–13% (db) resulted in the expected disappearance of the ice-melting transition and the shift of the temperatures of the glass–rubber transitions to 11–23 °C for the sucrose-rich phase (T2) and to 58–87 °C for the amylopectin-rich phase (T4). Wide angle X-ray diffraction was used to monitor the degree of order particularly to verify the amorphous state of sucrose in the blends over the sugar and water content ranges of interest. [Copyright &y& Elsevier]

The influence of less than 1% of κ-carrageenan on the mobility of glucose syrup was studied in the context of the glass–rubber transition using proton NMR relaxometry. Glass-transition temperatures, (Tg) were measured by differential scanning calorimetry (DSC) on glucose syrup samples containing 0 or 0.9% κ-carrageenan, between 0 and 1.4% KCl, and at water contents from 3.5 to 16% (wwb). Potassium chloride was added to vary the extent of gelation of the carrageenan in order to assess the effect of the biopolymer network on molecular mobility.Contrary to the reported increase of the rheologically determined glass-transition temperature, in the presence of gelling agents, the addition of 0.9% κ-carrageenan to glucose syrup with and without KCl, had no effect on the DSC measured Tg. In addition, there was no effect on molecular mobility in the glassy region. The presence of carrageenan only significantly affected the mobile part of the NMR free induction decay at relatively high temperatures. [Copyright &y& Elsevier]