Molecular order versus vitrification in high-sugar blends of gelatin and kappa-carrageenan.

摘要

The understanding of synthetic polymer viscoelasticity was applied to the small deformation properties of high-sugar gelatin and kappa-carrageenan mixtures. The glass transition zone in sugar/gelatin mixtures exhibited a dominant liquid-like response, which was followed by the method of reduced variables. The glass transition temperature predicted by the WLF/free volume approach coincided with the crossover of storage and loss modulus at the onset of the glassy state. The viscoelastic spectrum was resolved into a basic function of temperature and a basic function of time, thus rationalizing their effect on the vitrification of the mixture. Vitrification was only one in a plethora of viscoelastic properties. Manipulation of the composition of the mixture generated a continuous gelatin matrix or a viscous sugar phase suspending a dispersion of ice crystals. Besides the small-molecule crystallinity, vitrification can be halted by ordered macromolecular helices observed in the kappa-carrageenan/potassium system. Thus, the solid-like component of the sugar/kappa-carrageenan network remained prevalent over the predicted frequency window. The WLF equation was unable to follow the progress of viscoelastic functions, which were better described by an energetic barrier of rotation from one state to another.