‘Collapse’, a structural transition in freeze dried carbohydrates

Abstract

Abstract The influence of moisture, component molecular weight or binary mixture composition on Tc of freeze dried matrices was evaluated. It was shown that log(Tc) is linearly related to moisture content, with a break in the curve at approximately the BET monolayer. The collapse temperature, Tc, was inversely proportional to molecular weight for a homologous series of maltooligosaccharides. An expression giving the change in Tc for compositional changes in a binary mixture, with both components remaining amorphous, was shown to apply. Knowing the relationship between Tc and degree of polymerization enabled the prediction of Tc of any multi-component mixture of malto-oligosaccharides based on the general expression 1/Tc=ΣWi/Tci. Large increases in Tc in the presence of a crystalline phase was shown for freeze dried inositol-containing systems at high inositol contents. These results are discussed on the basis of structure in the freeze dried matrix.