Use of Ultrasound in the Extraction Process of Virgin Olive Oil and Influence on Malaxation Time.

The use of power ultrasonic in the olive oil industry is an innovative technique applied for the treatment of olive paste. The high-intensity sound waves exert a mechanical action by means of acoustic cavitation. Different operating parameters were applied in the milling operations to test the impact of the ultrasound treatment on the physical and chemical characteristics of the oils. The extraction tests were carried out with olives harvested at three different maturity stages and with three different durations for the malaxation phase, whereas the sonication time was the same for all treatments. The ultrasound US treatment was applied to the olive paste flowing through connection pipes in continuous operation, at 20 kHz frequency and 2.8 kW power. The yield and the organoleptic quality of the virgin olive oils extracted (VOO) were evaluated according to standard procedures. Three different malaxation times were used in oil extraction. The oIoil extraction yields progressively decreased with shorter malaxation time. The US treatment increases olive oil yield up to 22.7% when milling olives at an early ripening stage. In general, the ultrasonic treatment was found to increase the efficiency and speed of extraction, also giving olive oils enriched in bioactive compounds.