Scaling-up of supercritical solvent impregnation of olive leaf extract into polypropylene films

Abstract

The agricultural by-products of the olive sectorcontain a large amount of antioxidant andantimicrobial compounds that can be recoveredand reincorporated into a value chain. One of thetechnologies more used for extraction andpurification of these compounds, as well as fortheir incorporation into the polymers, are thoseusing high-pressure such as supercritical CO2.Although the scaling up of the extraction processis been studied, and even applied at an industrialscale, the impregnation process has never beenstudied beyond than laboratory scale. As well asthe extraction process, the impregnation processentails a mass-transfer process that requires anintricate balance between the solubilizationpower of the CO2, and the partition coefficient ofthe active substance, being favored towards thepolymer (1). There are several operationalparameters that alter that balance, which makesdifficult scaling of the process. This study isfocused on the scaling up of the supercriticalsolvent impregnation of an antioxidant olive leafextract (OLE) into a polypropylene film (PP).The scale-up process has been studied using threedifferent capacities of the impregnation cell: 100mL, 500 mL, and 2 L, maintaining constant theratio cm2film/VOLE in all tests. The 2 L-plantimpregnations were performed at 1 and 24 h.Results showed similar loading rates ofimpregnated compounds when working atdifferent scales, showing the good scaling up ofthe process (Figure 1). Regarding impregnationtime, the most suitable conditions to achieve thehigher antioxidant activity were shown at 1 h ofimpregnation. The identification of the maincompounds impregnated was determined byanalyzing the polymer surface by ImagingDesorption Electrospray Ionization MassSpectrometry (DESI-MS), showing a betterdispersion of luteolin-7-glucoside on the polymersurface, but a higher impregnation of oleuropein.