The influence of carrageenan on molecular mobility in low moisture amorphous sugars

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, (T_g) 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 T_g. 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.