Χρήση υπερκρίσιμων ρευστών για την εκλεκτική εκχύλιση ουσιών χρήσιμων στη βιομηχανία τροφίμων από κατάλοιπα ελαιουργείων

Abstract

The ultimate goal of this thesis is the study of whether olive-mill wastes could possibly offer compounds that have industrial use and whether such compounds may be removed from the wastes with supercritical fluid extraction. In order to ascertain this, the wastes of olive-mills are studied, specifically the solid state olive mill wastes, since the water phase has been studied in another thesis. From the solid state wastes, the olive pomace is the compound of interest, since the olive tree leaves are much less in mass and have already been studied elsewhere. Plenty of compounds can be found in the olive pomace, that can be used in the industry, with the main product being olive-pomace oil, which adds to the income of olive oil mills and refineries. Olive-pomace oil can be traded as is, but it also contains many compounds useful to the food and pharmaceutical sectors, mainly tocopherols, sterols, fatty acids and squalene. Selective extraction of these compounds is achieved with supercritical carbon dioxide (SC-CO2) extraction. This extraction is shown to have certain advantages over the standard solvent extraction, which the industry currently uses, since with small changes in the extraction conditions it is possible to extract selectively different compounds from the pomace oil. It is also cleaner and more environmentally friendly as it avoids the use of organic chemicals and it provides a solution to the diminishing population of sharks, whose liver is the current source for squalene. Supercritical fluid extraction has been researched widely over the past twenty years. It has been mentioned that supercritical fluids show densities that are similar to liquids, while keeping their viscosities in the same level as gases. The most common supercritical fluid is carbon dioxide, which can be found in abundance. CO2 and its properties are studied in this thesis and the way they change over different extraction conditions is shown, with emphasis on their influence over its dissolving and diffusion capability. Supercritical extraction may be central to this thesis, but it’s not the only chapter of it. All the necessary steps for the accurate study of the phenomenon are presented, from gathering the pomace to quality and quantity control of the compounds of the final extract. Gas and liquid chromatography for such control can be found herein, along with other techniques, used compounds and conditions. With the use of microscopy, the inside of pomace is presented and thus, the choice for mathematical modeling is explained. Various experiments have been done, with emphasis on the applied science, while the theoretical part is formulated with the determination of the mass transfer coefficients necessary for the prediction of the extraction in large scale. Optimization of the extraction is offered, with two goals in mind, one of oil mass production and another of a specific compound enrichment in the extract. Meanwhile it is proved that these two goals cannot be simultaneously achieved. Finally an effort has been made to determine the cost of the industrial use of this technology, and to compare it with the currently used solvent extraction technology.