Integrated microwave- and enzyme-assisted extraction of phenolic compounds from olive pomace

The olive pomace (OP) is an underutilized byproduct from the olive oil extraction that has the potential to be used as a source of antioxidant phenolics for nutraceutical applications. The simultaneous use of enzymes (cellulase, pectinase, and tannase) and microwave processing was evaluated with respect to OP phenolic extractability and composition. Microwave-assisted extraction achieved similar phenolic extractability (272 mg GAE/g OP) to conventional solvent extraction using water as a solvent, a higher solids-to-liquid ratio (1:15 vs. 1:50, g/mL), and a shorter reaction time (17 vs. 120 min). The use of enzymes during microwave processing led to increased extractability of phenolics (341 mg GAE/g OP) at higher extraction temperature (60 °C) and faster heating strategy (5 min ramp time). Microwave-enzyme-assisted extraction and enzyme-assisted extraction produced phenolic extracts with a higher concentration of phenolic alcohols (22–48 mg/kg) and acids (including hydroxytyrosol) (17–26 mg/kg). Mixtures of pectinase, cellulose and tannase biotransformed OP phenolics thus leading to the production of elenolic acid at 1029 mg/kg.