EVALUATION OF THE STATE OF OXIDATION OF OLIVE-POMACE OILS - INFLUENCEOF THE REFINING PROCESS

The aim of this investigation was to trace the fate of oxidation level s in crude olive-pomace oil during refining. Seven series of samples w ere examined. Each series comprised samples of the unprocessed crude o il and of the same oil collected after each step of the refining proce ss. The analyses were performed by means of silica gel column chromato graphy and high-performance size-exclusion chromatography. The data ob tained showed that triglyceride oligopolymers increased during refinin g, especially during bleaching and deodorization, and that the levels of these compounds were on average similar to 4-fold greater in the re fined oils than in the crude oils. Conversely, oxidized triglycerides decreased by an average of 49% as the oil was processed into a refined oil. When the percent values of oxidized triglycerides were plotted a gainst the percent values of oligopolymers, a linear trend of the expe rimental data was depicted for all the series examined. The regression lines computed revealed correlation between the two classes. This ind icated that one of the reasons oxidized triglycerides decreased during olive-pomace oil refining was related to the occurrence of polymeriza tion reactions. It was finally suggested that the content of oligopoly mers triglycerides may be usefully employed as a reliable analytical i ndex for estimating the level of oxidation of a freshly refined oil.