Temperature Effect on Drying and Swelling of Kappa Carrageenan Gels: A Steady State Fluorescence Study

Abstract

AbstractSummary: A novel technique based on in situ steady state fluorescence (SSF) measurements is introduced for studying drying and swelling of κ‐ carrageenan (kappa carrageenan) gels at various temperatures. κ‐ carrageenan gels were completely dried and then swelled in water vapor. Pyranine was embedded in κ‐ carrageenan and used as a fluorescence probe. Scattered light intensities, Isc and fluorescence intensities, I were monitored during the drying and swelling of κ‐ carrageenan gels. It was observed that the fluorescence intensity decreased linearly as drying time was increased. A simple model consisting of Case II diffusion was used to quantify the drying processes of the κ‐ carrageenan gels. This moving boundary model provided packing constant, k0. During swelling, fluorescence intensity increased exponentially as time is increased. The increase in I, was modeled using Li‐Tanaka equation from which swelling time constants, τc and cooperative diffusion coefficients, Dc were determined. It was observed that swelling time constants, τc decreased and diffusion coefficients, Dc increased as the swelling temperature was increased. Activation energies for drying and swelling were also obtained and found to be 53.9 and 47.2 kJ mol−1, respectively.