Encapsulation and retention of decanoic acid in sol-gel-made silicas.

Porous sol-gel-made silica particles are investigated as encapsulation matrices for controlled release of substances in food and pharmaceutical applications. Here the retention performance of an entrapped model flavor, decanoic acid, inside silica matrices made by hydrolysis of tetraethyl orthosilicate (TEOS) is studied. The retention of decanoic acid is measured by gas chromatography and thermogravimetric analysis. The morphology, specific surface area, porosity, and pore size distribution of the particle matrix is controlled by the sol-gel preparation method. During drying, the weakly cross-linked polymers in a slowly hydrolyzing silica gel deform and wrap around flavor molecules, creating a denser gel structure. There the flavor molecules are entrapped more efficiently than in fast-hydrolyzing matrices that result in more porous particles. Kinetic annealing studies show that flavor molecules are entrapped quite efficiently even at high temperatures.