Mechanistic interpretation of vitamin B6 transport from swelling matrices of genipin-crosslinked gelatin, BSA and WPI

Vitamin entrapment in matrices made of natural polymers and its controlled release has application to a variety of added value foods and nutraceuticals. This communication utilises data from published literature on the molecular transport of vitamin B6 from condensed matrices of genipin-crosslinked gelatin, bovine serum albumin and whey protein isolate to develop a mechanistic model that accounts for moving boundary conditions. In doing so, it utilises the apparent diffusion coefficient of the micronutrient, the molecular weight of the uncrosslinked polymer chain and the average molecular weight between neighbouring crosslinks. The derived mathematical expression for swellable matrices in an aqueous environment can follow the progression of diffusivity with degree of crosslinking in the polymeric excipients. Model fitting provides a minimisation parameter, which is interpreted in terms of the extent of coupling between solute diffusion and matrix structural relaxation. Parallel predictions of polymer network mesh and critical molecular weight between crosslinks indicate that values of normalised size well above one are required for anomalous (non-Fickian) release due to obstructed diffusion.