We investigate the effect of added KCl on the glass transition of potassium-κ-carrageenan/polydextrose and
molecular transport of caffeine. Samples were prepared with 2% (w/w) κ-carrageenan, 82% (w/w) polydextrose
and 1% (w/w) caffeine to a total solids level of 85% (w/w). KCl was added at 0, 50, 100 and 200 mM to induce a
dependence of structural properties on the potassium ion concentration. High-resolution spectral data over a
wide spectral range for the tertiary system were collected using Fourier transform infrared spectroscopy (FTIR),
which were complemented by tangible evidence of its morphology with scanning electron microscopy (SEM).
Work then focused on the estimation of the mechanical (Tgm) and calorimetric (Tgc) glass transition temperature
using in-shear dynamic oscillation and modulated differential scanning calorimetry (MDSC). Molecular transport
of caffeine in the condensed polysaccharide/co-solute system was followed with UV–vis spectroscopy over a wide
temperature range (− 20 to 30 ◦C) and modelled with extended diffusion theory. Time-dependent mass transport
of the diffusant was correlated to the structural relaxation of the polymeric matrix seen in increasing values of the
mechanical glass transition temperature with higher additions of potassium counterions to κ-carrageenan. It was
concluded that the mechanical glass transition temperature has a prominent effect on the release kinetics of
caffeine in these materials, as compared to the calorimetric glass transition temperature.