Effect of oligomeric or polymeric additives on glass transition, viscosity and crystallization of amorphous isomalt

The main purpose of this study was to further improve the stability of the amorphous state of isomalt by the addition of high molecular weight compounds. Differential scanning calorimetry (DSC) was used to determine the glass transition temperature T-g of a series of polyol mixtures containing isomalt as a function of water content. As expected, for each mixture T-g decreased with increasing moisture. Only with the addition of more than 75% of higher molecular weight compounds to isomalt an increase of Tg could be achieved. Moisture content and time dependent phase transitions in the metastable amorphous state of the mixtures strongly affect the storage stability of isomalt hard candies. Storage tests indicated a markedly accelerated water absorption and crystallization when oligomeric or polymeric compounds were added to amorphous isomalt. Rheological experiments showed that in contrast to pure isomalt melts, the viscosity of melts containing oligomeric or polymeric additives deviated from the model curve predicted by the Williams-Landel-Ferry-kinetics (WLF) with increasing water content. (C) 2000 Elsevier Science Ltd. All rights reserved.