Starch gelatinization temperature in sugar and polyol solutions explained by hydrogen bond density

Abstract

In this paper we show that the shift of the gelatinization temperature of starch in sugar and polyol solutions is explained by nOH,eff, the volumetric density of hydrogen bonds in the solutions. nOH,eff is computed using the dry glass transition temperatures of the low molecular weight carbohydrates. This correlation of starch gelatinization temperature to nOH,eff is shown for 19 different sugar and polyol compounds in solutions at different concentrations, as measured in an earlier study by Allan et al. (2018). The earlier study found that the measured viscosity of the solutions best correlated to starch gelatinization temperature, but it was assumed that there is a more fundamental property of the sweetener that alters both the viscosity and the starch gelatnization behaviour. Here, it is shown that nOH,eff is this fundamental property responsible for controlling both the viscosity and starch gelatinization temperature differences in the used sugar and polyol solutions. Because nOH,eff is also related to Tg, the glass transition temperature of the carbohydrate solutions, the viscosity of a wide variety of carbohydrate solutions can be mapped to a single master curve if plotted against Tg/T, the ratio of glass transition and the actual temperature. Older hypotheses concerning the shift of the starch gelatinization temperature in carbohydrate solutions have explained it in terms of water activity. However, we show that nOH,eff relates to water activity only for carbohydrates with similar molecular weights. We conclude that sugar and polyol solutions can be viewed effectively as a single solvent, which is characterized by nOH,eff. This measure for volumetric density of hydrogen bonds in these solutions can be used to predict the starch gelatinization temperature in different formulations.