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

摘要

A novel technique based on in situ steady state fluorescence (SSF) measurements is introduced for studying drying and swelling of k- carrageenan (kappa carrageenan) gels at various temperatures, k- carrageenan gels were completely dried and then swelled in water vapor. Pyranine was embedded in k- carrageenan and used as a fluorescence probe. Scattered light intensities, I_(sc) and fluorescence intensities, / were monitored during the drying and swelling of k- 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 k- carrageenan gels. This moving boundary model provided packing constant, k_o. 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, τ_c and cooperative diffusion coefficients, D_c were determined. It was observed that swelling time constants, τ_c decreased and diffusion coefficients, D_c 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.