Rate of fatty acid transport in glassy biopolymers: A free volume based predictive approach

Metastable properties of biopolymer networks affect significantly the diffusion kinetics of bioactive compounds. That was shown to be the case in high solid samples of protein and polysaccharide supporting a homogeneous distribution of polyunsaturated fatty acids. Thermomechanical behaviour of these matrices was characterised in relation to their glass transition temperature (Tg). A free volume theory of diffusion was considered to treat transport phenomena of fatty acids within glassy polymers. It was found that at T > Tg the effective diffusion coefficient of microconstituent transport would increase in accordance with the free volume of the polymer matrix. Fitting experimental diffusivity data in glassy polymers to a free volume based theory generates a two-parameter equation that calculates the extent of molecular interaction between macromolecule and microconstituent. Gradual substitution of polymer with small-molecule co-solute, glucose syrup in this case, induces a plasticising effect that profoundly affects the level of interaction, hence the diffusion of fatty acids in the condensed biomaterial. © 2017