Investigation of the impact of different sugar compositions on the moisture absorption of hard candy when exposed to a humid environment

Abstract: Hard candy is hygroscopic, implying that hard candy readily absorbs moisture from the environment, resulting in adverse changes in the texture and appearance of the candy. This thesis investigates the impact of different sugar compositions on the moisture absorption of hard candy when exposed to a humid environment. Five different hard candy formulations were exposed to an 8-day storage experiment at 75% relative humidity, allowing the candy to change over time. Moisture content, water activity, crunchiness, colour diffusion, and moisture absorption were analysed throughout the experiment. ANOVA and ImageJ were used to analyse the data. Promising outcomes were observed in formula 1 (9,8 DE) regarding reduced moisture absorption and improved stability of crunchiness and colour diffusion compared to the other formulations. A correlation between molecular weight sugars and moisture absorption was observed. The absence of hygroscopic low molecular weight sugars combined with the presence of high molecular weight sugars mitigates moisture absorption. This saccharide composition also increases the stability of colour diffusion and crunchiness, as in formula 1 (9,8 DE). The moisture absorption of all formulations showed an initial increase, implying rapid moisture absorption at the surface. Followed by a slower increase due to the decreasing driving force. Then, an exponential increase in moisture absorption is observed with a high calculated diffusion coefficient. This data indicates a phase transition from a glassy to a rubbery state with high mobility, resulting in a higher moisture migration rate. Formulas 1 (9,8 DE) and 2 (13 DE), with a small amount of low molecular weight saccharides, show lower diffusion coefficients, indicating a delayed transition to the rubbery state and better retention of crunchiness.