An overview of emerging techniques in virgin olive oil extraction process: strategies in the development of innovative plants

Currently the systems for mechanically extracting virgin oils from olives are basically of two types: discontinuous-type systems (obsolete and dying out) and continuous-type systems. Systems defined as “continuous- type†are generally comprised of a mechanical crusher, a malaxer and a horizontal-axis centrifugal separator (decanter). The “continuous†appellation refers to the fact that two (mechanical crusher and decanter) out of the three machines making up the system operate continuously; the malaxer, which actually is a machine working in batches, is located between these two continuous apparatuses. Consequently the malaxation represents the bottleneck of the continuous extraction process. The entire virgin olive oil (VOO) process has changed very little over the last 20 years. One of the essential challenges of VOO industrial plant manufacturing sector is to design and build advanced machines in order to transform the discontinuous malaxing step in a continuous phase and improve the working capacity of the industrial plants. In recent years, rapid progress in the application of emerging technologies in food processing has been made, also in VOO extraction process. Ultrasounds (US), microwaves (MW), and pulsed electric fields (PEF) are emerging technologies that have already found application in the VOO extraction process on pilot scale plants. This paper aims to describe the basic principles of these technologies as well as the results concerning their impact on VOO yields and quality. Current and potential applications will be discussed, taking into account the relationship between the processing, the olive paste behavior and the characteristics of the resultant VOO, as well as recent advances in the process development.