Sugar vs. Sugar Substitutes in Condensed Dairy Products: Electron Microscopy and Rheology

Publications on functional condensed dairy foods focus on the formulation without considering the intermolecular interaction between a particular sweetener and casein micelles. Consequently, the structuring processes remain largely understudied. Electron microscopy and rheological studies may provide important data about the structure and mechanics of this interaction. This article introduces a comparative structural analysis of a condensed dairy product with sugar and its low-calorie substitute allulose. The research included fresh and 14-month-old original prodct with sugar and its experimental samples where sucrose was substituted with 40 and 60% allulose. The structural analysis involved the methods of electron microscopy and rheology. The physicochemical parameters and sensory profile were studied using standard methods. The electron-microscopic studies of the structures formed by casein micelles showed that 40% allulose had no effect on their morphometry. However, replacing 60% sucrose with allulose destroyed casein micelles, encapsulating them with saccharide and forming dense aggregates, which spoiled the sensory and physicochemical quality of the final product. The excessive fluidity of the product was due to a 27% decrease in viscosity. In this study, replacing more than 40% of conventional sweetener with allulose damaged the quality of the functional condensed dairy product.