Effects of lipids on the water sorption, glass transition and structural strength of carbohydrate-protein systems

peer-reviewedEncapsulant systems are gaining wide practical interest due to their functional and nutritional properties. This paper was focusing on understanding structural relaxations in that systems near glass transition temperature. Freeze-dried trehalose-whey protein isolate-sunflower oil systems with various ratios of the last were used as a carbohydrate-protein-lipid food model. The Guggenheim-Anderson-de Boer (GAB) water sorption relationship was used as a tool to model water sorption isotherms. The glass transition temperature was obtained by differential scanning calorimetry (DSC). Structural α-relaxation temperatures were measured by dynamical mechanical analyses (DMA), dielectric analysis (DEA) and combined to cover a broad range for strength assessment. The microstructure was characterized by optical light microscopy, confocal laser scanning microscopy and scanning electron microscopy. The C1 and C2 constants for Williams-Landel-Ferry (WLF) equation and structural strength parameter were calculated for each system. The effect of sunflower oil and water contents on strength of carbohydrate-protein system was analyzed. Strength shows decreasing with increasing of lipid concentration in the mixtures and more complex dependence on the water content in a system.This investigation was supported by the Food Institutional Research Measure (FIRM) project “Formulation and Design for Food Structure and Stability” funded by the Department of Agriculture, Food and Marine (11-F-001), coordinated by prof. Y.H. Roos, UCC, Ireland and by the Food Institutional Research Measure (FIRM) project “Developing the next generation of high protein spray dried dairy powders with enhanced hydration properties” (15-F-679) funded by the Department of Agriculture, Food and Marine, coordinated by Dr. Mark Auty, Teagasc Food Research Centre, Moorepark, Co. Cork, Ireland