Food microencapsulation of bioactive compounds: Rheological and thermal characterisation of non-conventional gelling system

Microencapsulation is a powerful technique commonly used for the protection of a wide range of biomolecules (small molecules and protein) and cells of bacterial, yeast and animal origin. In this work, solutions of mixed biopolymers are investigated as excipients for the formulation of a model system. The influence of the different components is studied from the viscoelastic behaviour of the starting solutions to the thermal characterisation of the gel beads therefrom produced. Rheological characterisation displays an almost regular trend for the several combination of solutes and for the frequency dependence, but some peculiarities emerge when both the model protein lysozyme and the cosolvent ethanol are present in the mixture; for the latter system a delayed melting behaviour of water appears in the gel beads. Changes in the temperature dependence of water evaporation from the beads are taken as an evidence of the rate of release from the beads.