Critical water activity of disaccharide/maltodextrin blends

Critical water activity ( a w ∗ ) is employed in this study as a practical metric of the hygroscopic stability of multi-component carbohydrate glasses. Glass transition temperature (Tg) and water activity (aw) data are modeled to determine the aw at which sufficient moisture is present to yield a Tg value of 25 °C (i.e., the a w ∗ ). The results confirm the well-known effect of decreasing sensitivity to moisture with increasing molecular weight. The results also demonstrate the additional influence of molecular type. The hygroscopic stability of binary maltodextrin/disaccharide systems increased in the same order as the glass transition temperature of the disaccharide: sucrose < maltose < trehalose. General equations are proposed for predicting the a w ∗ of mixtures, which could be used towards the formulation of stable glassy products.