Evaluation of the state of oxidation of crude olive-pomace oils. Influence of olive-pomace drying and oil extraction with solvent

The aim of this investigation was to follow the progress of oxidation during the phases of the industrial process of olive-pomace drying and the subsequent step of crude pomace oil extraction with solvent. Silica-gel column chromatography and high-performance size-exclusion chromatography were the analytical techniques utilized to this purpose. The data obtained showed that most of the oxidation occurs during industrial drying of the pomace with a mean increase of 35% in the oxidized triglycerides while no statistically significant increase was observed for triglyceride oligopolymers. The subsequent extraction of oil with solvent and the removal of the last traces of commercial hexane for the preparation of crude olive-pomace oil did not seem to entail any substantial increase in oxidation. There was a change in the state of oxidation given that there was art increase in triglyceride oligopolymers, which on average reached 0.32%, and in secondary oxidation products (mean p-anisidine value = 15.31). Hydrolytic degradation of elude pomace oils was particularly high with a mean value of free fatty acids of 9.24% and of diglycerides of 5.75%