Moisture and Temperature Triggered Release of a Volatile Active Agent from Soy Protein Coated Paper: Effect of Glass Transition Phenomena on Carvacrol Diffusion Coefficient

Carvacrol release from SPI-coated papers was evaluated at different relative humidities (RH; 60, 80, and 100%) and storage temperatures (5, 20, and 30 degrees C). Effective carvacrol diffusivities were determined from experimental release kinetics and by using a mathematical model based on Fick's second law. Increasing storage temperature and RH lead to an increase of carvacrol diffusivity. Depending on the relative humidity, the carvacrol effective diffusivity varied from 1.71 x 10(-16) to 138 x 10(-16) m(2)/s at 30 degrees C, from 0.85 x 10(-16) to 8.78 x 10(-16) m(2)/s at 20 degrees C, and from 0.11 x 10(-16) to 7.50 x 10(-16) m(2)/s at 5 degrees C. The combined effect of relative humidity and temperature on diffusivity was particularly marked at 30 degrees C and 100% RH. The temperature and relative humidity dependence of carvacrol release was related to the glass transition phenomenon and its effect on chain protein mobility and carvacrol diffusivity.