The olive fruit contains around 12 – 30% oil by mass, depending largely on cultivar, maturity stage and environmental conditions.
The oil is located in the mesocarp (flesh cells); largely in the vacuoles and to a lesser extent spread through the colloidal tissue of the cytoplasm. Some oil is found in the seed kernel and therefore the entire fruit is milled and processed for oil extraction. The crushed seed fragments also facilitate the extraction process. About 85 – 90 percent of the oil can be extracted using standard procedures, which are purely mechanical, involving no chemicals and occurring at room temperature.
As soon as practically possible (within 24 hours) harvested fruit is washed in automatic washing machines to remove dust, leaves and any other foreign matter that may have come in from the orchard. The olives are then passed through a crusher (either a hammer-mill or blade crusher) which crushes the entire fruit into a paste, with the aim being to break up the flesh cells of the fruit. High speed crushers can cause an oil/water emulsion to form.
The crushed olive paste is then then churned by paddles in a malaxer to further break up the fruit cells, to break up the oil/water emulsion and to help coalesce the micro-droplets of oil into larger drops until they form “pockets” that can be easily separated as a continuous liquid phase from the other phases. This malaxing should take place at temperatures high enough (around 25 to 30 oC ) and for a long enough time (about 30 to 45 minutes) to facilitate sufficient release of oil but not so high or so long as to affect oil quality negatively. Extended contact of paste with oxygen (air) during this time also has a negative effect on oil quality. Expert millers learn from experience the best settings for different olive cultivars, maturity stages, climatic and growing conditions.
SA Olive introduces “FOLLOW THE OLIVE”
An in-depth look at the journey our beloved olives take from as early as being planted to the end of their life-cycle… being tasted and enjoyed! We look forward to sharing snippets of fun and fascinating information with you over the course of the year.