• Malaxation;
  • Process improvement;
  • Ultrasound-assisted extraction;
  • Virgin olive oil

Malaxation is a basic step in the mechanical olive oil extraction process that may affect yield, quality, and health properties of virgin olive oil (VOO). The operative conditions of malaxation, such as temperature and time, are fundamental to favor the oil coalescence process and, consequently, the duration of the VOO extraction process. The aim of this study was to improve the extraction process efficiency by using an ultrasound treatment of olive paste before the malaxation step. The ultrasonic treatment was applied to Coratina and Peranzana, which are two of the most popular Southern Italian olive varieties characterized by extremely different technological performance. Different times of ultrasound treatments were tested (0, 2, 4, 6, 8, 10 min) and free acidity, peroxide value, K232, K270, sensory analysis, tocopherols, total carotenoids, chlorophyll, and total polyphenols were determined. Results showed that the ultrasound treatment caused a quick heating of the olive paste as a function of the ultrasound treatment time. Times of treatment of 8 and 10 min allowed the reduction of the malaxation phase from 60 to about 40 min. The ultrasound technique improved antioxidant content in both VVOs, except for polyphenols that decreased. However, the reduction of polyphenol concentration in Coratina VOO improved its taste by reducing the bitter and pungent notes, which are not always accepted by consumers.

Practical applications: In this study we propose an innovative application of ultrasound in VOO processing. Ultrasound treatment was applied to olive paste before malaxation in order to increase the process efficiency by reducing the malaxation step. Further, this strategy makes it possible to reduce the number of kneaders, thus reducing the plant costs. The resulting VOO after the ultrasound treatment presents a more harmonic taste and an appealing and desirable color when applied to a variety notoriously characterized by strong bitter and pungent notes such as Coratina, making the oil more attractive for consumers with respect to the traditional ones.