Effect of starch xero- and aerogels preparation on the supercritical CO2 impregnation of thymol

Abstract

In this study, for the first time, the supercritical solvent impregnation (SSI) technique has been used to test the incorporation of thymol into starch gels. Corn and tapioca starch hydrogels prepared at different temperatures (70-100 degrees C) were converted to the acetogels and subsequently dried with supercritical CO2 or air to obtain aero- or xerogels, respectively. Starch xero- and aerogels were impregnated with thymol in a high pressure view cell using supercritical CO2 at 15.5MPa and 35 degrees C during 24h. The influence of the botanical origin of starch, temperature for hydrogels preparation (Tgel-h) and drying method on the gel morphology and thymol impregnation yields was discussed. Determined thymol SSI yields were in the range of 1.15-4.02% for the corn and 0.58-3.63% for the tapioca starch gels. Xerogels had higher thymol loading capacities (1.76-4.02%) than aerogels (0.58-3.31%) at given SSI conditions. Gel morphology and thymol SSI yields were positively affected by the Tgel-h increase. The xerogel obtained from the corn starch hydrogel prepared at 100 degrees C had the largest specific surface area (5.52m(2)/g) and thymol loading capacity (4.02%) at given SSI conditions. These results, along with a simple and low-cost production, indicated the great potential of the corn starch xerogel for commercial use as a carrier in pharmaceuticals and nutraceuticals.