Encapsulation of Antioxidant in Hidrophobic Silica Xerogel

M. V. REVUELTA; M. B. FERNÁNDEZ VAN RAAP; P. MENDOZA ZÉLIS; F. H. SÁNCHEZ; G. CASTRO

Curitiva

Congreso; 4th International Congress of Bioprocesses in the food industry; 2010

p { margin-bottom: 0.21cm; } The area of biocompatible materials is burgeoging, among them composite aerogels are promising for industrial applications because of are chemically inerts and non-harmful to human body. Aerogels are very versatile dried gels with high pore diameter, generally between 2 to 50 nm. The aims of the present work is to study hydrophobic silica aerogel as a carrier for controlled release of sensitive molecules like ascorbic acid (AA) to be used in food packaging. AA is an essential nutrient in human diet with antioxidant properties as well. Free AA stability is very sensitive toenvironmental conditions such as temperature, light, oxygen, pH and water activity, which are reducing its biological activity. AA encapsulation and/or entrapment in an inert matrix is an alternative to keep AA activity protected for the development of AA-fortified food. Hydrophobic silica aerogel were made easily following one-step procedure in presence of tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS) containing AA and methanol-water solvent mixture. Characterization of AA loaded and unloaded aerogels were performed with FTIR and XRD. FTIR analysis of silica aerogels showed the characteristic vibrational peaks of SiO2 at 780 cm-1 (Si-O(b), bending mode) and 1070 cm-1 (Si-O(s), asymmetric stretching mode). However, When AA was entrapped in the aerogel, the carbonyl stretching (C=O(s)) mode of AA was shifted from 1754 cm-1 to 1738 cm-1 indicating a strong interaction with the matrix. In addition, a displacement of at least one hydroxyl group strectching (O-H(s)) mode was shifted from 3624 cm-1 to 3628 cm-1, that could be possible because of H-bridge fomration with SiO2 matrix. X-ray analysis showed two broad reflection lines which peak at 2teta = 11 and 23 degrees corresponding to amorphous silica. For loaded aerogels the structure is expanded, the 11 degree peak shift to lower angles when AA is incorporated. Results indicate that AA molecules were incorporated to silica structure. Kinetic of AA release from silica aerogel granules were followed at 37ºC and 150 rpm. AA concentrations were quantified by high performance liquid chromatography (HPLC). The hidrophobic silica gel was very stable in aqueous medium pH 5. About 10% of AA was released at constant rate from the gel between 3 to 4 hours, showing high potential for a wide range of applications in the development fortified food packaging.