A DSC study of hydrated sugar alcohols. Isomalt

A DSC study has been carried out on isomalt, a commercial sugar alcohol der ived from sucrose and widely used as a sweetener in the food industry. Isom alt is a mixture of two isomers: alpha -D-glucopyranosyl-1-6-mannitol (GPM) and alpha -D-glucopyranosyl-1-6-sorbitol (GPS). Release of the water of cr ystallisation (around 100 degreesC) and melting (around 150 degreesC) have been phenomenologically characterised using different scanning rates and he at treatments. The effect of dehydration/re-hydration on the melting has be en investigated. The isomalt glass transition, at about 60 degreesC, was st udied on samples cooled after melting. The dynamic aspect of structural rel axation of isomalt has been quantified by its fragility parameter. Glassy s tate stability has been evaluated by performing ageing experiments at sub-T -g temperatures. During ageing, apart from the expected enthalpy relaxation effects, isomalt showed a peculiar behaviour, due to its isomeric composit ion. These preliminary and phenomenological results have been interpreted i n terms of isomer structure and of carbohydrate-water interactions in the m ixture.