The utilization of solid carbon dioxide in the extraction of extra-virgin olive oil: influence on oil profile

The aim of this research is the evaluation of the chemical profile of extra-virgin olive oil extracted by an innovative technology. The pre-milling addition of solid carbon dioxide CO2,s (carbonic snow) directly to the olives, promoting the olive cryomaceration, is the operation which marks this new extraction system. The addition of CO2,s (sublimation point: T=-78.5°C; P=1atm) to the fruits induces the intracellular water freezing and the consequent laceration of cellular membranes could induce the diffusion in liquid phase of many cellular compounds. Furthermore, the gaseous CO2 has a higher density compared with the air (dCO2,g /dair = 1.5), so it forms a gaseous inert layer on the surface of the olive paste, protecting it from the oxygen of the surrounding atmosphere. This gaseous inert layer allows to modulate the malaxation time and to manage the olive paste exposition to oxygen, improving the aromatic profile of extracted oil. The extraction runs were carried out utilising a micro olive-press (Oliomio Baby ®, produced by “Toscana Enologica Mori”, Tavarnelle Val di Pesa - Italy), which is able to mill 2030 kg of olives, and it was suitably modified to allow the addition of carbonic snow directly to olive fruits and/or to their paste. The effect induced on oil yield and on quality by olives cultivars, maturity index, moisture contents, time and conditions adopted during the olives storage and amount of added CO2,s, were analysed and compared with data obtained utilising the same raw materials without cryogen addition.The addition of the CO2,s seems to improve the extraction yield, a parameter which depends on many variables: ripeness degree and water content of the olives, time and conditions adopted during their storage, ratio between cryogen and olives (w/w). This innovative technology allows to extract an extravirgin olive oil richer in Vitamin E and bioactive components able to increase the oil antioxidant activity and so both its nutritional value and its shelf-life. This technology leads to an evident and immediate advantage for the olive producers, who could obtain a higher payment for the same amount of olives brought to the extraction plant. Besides the cryo-extracted oil should be richer in the aromatic substances that are typical of the raw material but are also linked to the production area and obviously to the pedoclimatic conditions. As a consequence, the cryo-extracted oil should be more linked to its production area and therefore easily recognizable by the consumer.