Impregnation of flax oil in pregelatinized corn starch using supercritical CO2

Polymer impregnation of active components using supercritical carbon dioxide (SC-CO2) has been studied for pharmaceutical and material processing applications, but only to a limited extent for food systems. SC-CO2 has the ability to diffuse into the amorphous or glassy regions of polymers, resulting in polymer swelling. This study was carried out to evaluate the behavior of pregelatinized corn starch (PGS) in SC-CO2 and to determine its potential impregnation with oleic acid and flax oil in SC-CO2 media. Starch was mixed with either oleic acid or flax oil and held in SC-CO2 at 15 or 30 MPa and 40, 60 or 80 degrees C under static or dynamic conditions. The resulting particles were analyzed to determine impregnation efficiency. Scanning electron micrographs confirmed the effectiveness of the washing treatment employed to remove surface oil. The SC-CO2 treatment did not affect PGS particle size. Higher impregnation efficiencies were obtained with oleic acid compared to those obtained with flax oil. For oleic acid, the highest efficiency was found at 40 C and 15 MPa (11.4% w/w) under static conditions, while for flax oil, only 6.6% (w/w) impregnation efficiency was achieved at 30 MPa and 80 degrees C and there were no significant differences among treatments. Both solubility and diffusion of oleic acid or flax oil in SC-CO2 play an important role in the impregnation process. Findings indicate that SC-CO2 technology has potential for food-grade polymer impregnation targeting nutraceutical delivery. (C) 2011 Elsevier B.V. All rights reserved.