Production in large quantities of highly purified hydroxytyrosol from liquid-solid waste of two-phase olive oil processing or "Alperujo"

The effect of hydrothermal treatment of two-phase olive waste (alperujo) on the solubilization of hydroxytyrosol was studied. Different conditions of saturated steam were assayed. A high amount of hydroxytyrosol was solubilized and increased with increasing steaming temperature and time, reaching 1.4-1.7 g/100 g of dry alperujo. The effect of acidic (H(2)SO(4)) and basic (NaOH) catalysts was also evaluated. Acid-catalyzed treatment was more effective at milder conditions, whereas the alkali-catalyzed conditions were not very suitable. In the present study, the extracted hydroxytyrosol was purified by means of a new, simple, and inexpensive chromatographic system, under international patent application (PCT/ES02/00058). From 1000 kg of alperujo, with 70% humidity, can be obtained approximately 4.5-5 kg of hydroxytyrosol. After a purification process, at least 3 kg of hydroxytyrosol, at 90-95% purity, would be obtained. The purified compound was identified by HPLC/UV and (1)H and (13)C NMR analyses, and its antioxidant activity was tested on refined olive oil without antioxidants by Rancimat method. The oxidative stability of refined olive oil was increased by a factor of 1.71 in the presence of 100 ppm of hydroxytyrosol.