Ultrasound-Assisted Production of Virgin Olive Oil: Effects on Bioactive Compounds, Oxidative Stability, and Antioxidant Capacity

This study examined the effects of ultrasound (US) treatment of olive paste before malaxation on oil yield (Y), enzyme activity and virgin olive oil (VOO) quality in four Croatian olive varieties: Istarska Bjelica, Rosulja, Oblica and Levantinka. Oils were extracted using the Abencor system following a central composite design, with treatment times of 3–17 minutes and power levels of 256–640 W. Parameters analyzed included Y, oxidative stability (OSI), antioxidant capacity (AC), phenolic and α-tocopherol content, volatiles, fatty acid profile and the activity of lipoxygenase, β-glucosidase, polyphenol oxidase and peroxidase. Olive variety had the most significant influence across variables. Response surface methodology revealed that US treatment at low to moderate intensity improved certain quality traits. For example, Y increased by 4% in Oblica, phenolic content rose by up to 17% in Istarska Bjelica, and OSI and AC were enhanced up to 13–14% in Istarska Bjelica and Levantinka. However, prolonged exposure and high US power had adverse effects. Other investigated parameters showed no significant changes. The application of US resulted in measurable, although moderate, improvements in Y and VOO quality, with outcomes strongly influenced by olive variety and treatment conditions. These findings highlight the importance of further optimization tailored to each specific variety. In addition, a feasibility study is warranted to evaluate the practical implementation of US technology in VOO production, considering the relatively limited benefits observed.