(109a) Supercritical Impregnation of Walnut Husk Extract into Polyethylene Film

Spencer-Williams, I. - Presenter, University of Pittsburgh
One of the biggest challenges in packaging products, specifically food products, is the need to inhibit microbial growth, spoilage, and the adverse effects those have. Active Packaging, such as those produced by impregnation of antioxidant compounds into films using supercritical fluids, have been demonstrated in other studies to increase shelf-life of packaged fruit and other goods. Supercritical fluids are fluids above their critical point, and exhibit high diffusivity, both liquid and gas like properties, and in the case of supercritical carbon dioxide, the ability to swell polymers. Due to this ability and a low critical temperature of 31 °C, supercritical carbon dioxide can be used to impregnate plant extracts into polymer films. In this study, antioxidant, polyphenolic compounds are extracted from the green husks of North American walnuts, and simultaneously, impregnated into low-density polyethylene (LDPE) films.
Impregnation tests were carried out in a 500 mL, agitated, high-pressure reactor using supercritical carbon dioxide with a 15 mol-% ethanol modifier at 60 °C and constant walnut husk to ethanol mass ratio. The effects of varying pressure from 2400 to 3200 psi, and impregnation time from 1 to 3 hours was evaluated. After impregnation, film samples were characterized using infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), as well as other tests. FTIR shows that walnut husk extract was successfully impregnated into LDPE films. These results will be presented and compared against a control.