Effect of oligomeric or polymeric additives on glass transition, viscosityand 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 compoun ds. Differential scanning calorimetry (DSC) was used to determine the glass transition temperature T-g of a series of polyol mixtures containing isoma lt as a function of water content. As expected, for each mixture T-g decrea sed with increasing moisture. Only with the addition of more than 75% of hi gher molecular weight compounds to isomalt an increase of Tg could be achie ved. Moisture content and time dependent phase transitions in the metastabl e 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 pol ymeric additives deviated from the model curve predicted by the Williams-La ndel-Ferry-kinetics (WLF) with increasing water content. (C) 2000 Elsevier Science Ltd. All rights reserved.