Extraction and encapsulation of bioactive compounds from olive mill pomace: influence of loading content on the physicochemical and structural properties of microparticles

Abstract

Extraction and encapsulation techniques can be combined to reduce the environmental impact of olive mill pomace (OMP) wastes due to their high content of phenolic compounds with biological properties. In this sense, this study aimed to obtain bioactive compounds from OMP by an optimized two-step solid-liquid extraction, followed by its encapsulation by a double emulsion solvent evaporation technique using ethylcellulose (EC) as a carrier. The bioactive compounds present in OMP extract were quantified by a reserved phase high-performance liquid chromatography, and the major phenolic compound identified was hydroxytyrosol, followed by tyrosol. The OMP extract was encapsulated at two loadings (5 and 10% w/w), and the obtained microparticles were characterized concerning encapsulation efficiency, loading contents, recovery of powders, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy, thermogravimetric analysis, particle size distribution, water absorption index, water solubility index, swelling capacity, and wettability. The microparticles showed high encapsulation yields (above 75%) and high encapsulation efficiencies (above 80%) with a high content of phenolic compounds with antioxidant activity. FTIR spectrum of microparticles revealed physical interactions between the compounds present in OMP extract and the functional groups of EC, indicating that the main bioactive compounds were intact and encapsulated. Microparticles were thermogravimetrically stable in the range of 30 to 280 °C, and exhibited outstanding granular stability. The results of this study provide perspectives regarding the incorporation of extracts obtained from agricultural residues into microparticles that can be later embedded in added-value products for the food industry. (c) 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.