Molecular dynamics of the diffusion of natural bioactive compounds from high-solid biopolymer matrices for the design of functional foods

Delivery of techno- and bio-functionality in all-natural processed foods is an area of steadily increasing fundamental and technological interest. One of the main aspects in this field is based on the diffusion of natural bioactive compounds that have been incorporated in high-solid biopolymers matrices. Organoleptic considerations dictate that the delivery vehicles are characterised by a highly amorphous fraction in the biopolymer network. Molecular diffusion in the amorphous state is a complex process associated with the effect of the glass transition temperature (Tg) on the mobility of low molecular-weight bioactives. This work will review the molecular dynamics of high-solid biopolymer systems, and model food preparations in the presence of co-solute, in relation to the diffusion kinetics of natural bioactive compounds. Literature indicates that the metastable properties of condensed biopolymer networks traversing the rubber-to-glass transition region affect significantly the diffusion kinetics of bioactive compounds. These have been modelled using concepts from the classical and improved diffusion theory to unveil a relationship between apparent diffusion coefficient of bioactives and free volume characteristics of the condensed biopolymer network. Further work is required in added value foods, sourcing inspiration from the "sophisticated pharmaceutical research" to develop food systems that control transport phenomena for targeted release from a specific dosage form.