Sugar Crystallization and Glass Transition as Destabilizing Factors of Protein-Stabilized Emulsions |
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Authors: | Leonardo Cornacchia and Yrj? H Roos |
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Institution: | (1) School of Food and Nutritional Sciences, University College Cork, Cork, Ireland; |
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Abstract: | Temperature cycling across the glass transition of the aqueous phase of oil-in-water emulsions stabilized by whey protein
isolate was considered as a possible factor affecting stability. Emulsions were formulated with an aqueous phase containing
80% (w/w) fructose, fructose:glucose 1:1 or glucose, in order to prepare a glass forming aqueous phase with sugar concentration
corresponding to that of the unfrozen phase of the maximally freeze-concentrated solutions. This allowed thermal cycling across
the glass transition in the absence of the formation of ice crystals. Emulsion stability was studied using differential scanning
calorimetry, dynamic light scattering and by visual analysis of the morphology of the systems. Emulsified systems undergoing
glass transition cycles of the aqueous phase did not show destabilization of the dispersed (crystallized) lipid phase. Sugar
crystallization in the aqueous phase, which occurred when glucose systems were stored above the Tg, led to emulsion breakdown. In this study, the formation of a glassy structure in the continuous aqueous phase preserved
the interfacial structure of WPI, thus protecting the dispersed lipid phase from destabilization. On the contrary, glucose
crystallization caused disruption of the interfacial membrane structure and loss of integrity of the interface which resulted
in extensive lipid phase destabilization. |
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Keywords: | |
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