Chapter 9 - Oil extraction and processing biotechnologies

Abstract

This chapter focuses on recent advances in olive oil extraction and processing. The olive oil extraction process refers to extracting the olive oil that is present in the olive fruits, botanically termed “drupes,” for food use. In olive fruits the oil is produced in the mesocarp cells, and stored in a particular type of vacuole called a lipovacuole. Hence, olive oil extraction can be said to be a process of separating the oil from the other fruit contents (vegetation tissue, water and solid material), and this separation is done only by physical means. The olive oil extraction process is normally divided into crushing, malaxation (mixing), and separation of the oil. The traditional method of olive oil extraction is by using an olive press. The main advantages of the traditional method are that it produces good-quality oil by more efficient grinding of the olives, reducing the release of oil oxidation enzymes, and that it also reduces added water, which minimize the washing of polyphenols. The modern method of olive oil extraction uses an industrial decanter to separate all the phases by centrifugation. The most common industrial processing method is a continuous extraction system with two centrifuges. It is widely accepted that, apart from polyphenols, most of the other olive oil-quality parameters (such as free fatty acids, peroxide values, ultraviolet absorption and sensory character) are not generally affected by the different modes of extraction, provided high-quality olive fruits are used and harvesting is carried out at the optimum time period. Efforts have been made to use natural enzymes or enzyme preparations (vegetable extracts) to enhance the mechanical extraction system during olive fruit processing.