The use of polyphenolic extract, purified hydroxytyrosol and 3,4-dihydroxyphenyl acetic acid from olive mill wastewater for the stabilization of refined oils: a potential alternative to synthetic antioxidants

Ethyl acetate extracts of olive mill waste water (OMWW) were prepared, under in optimal conditions, using a continuous countercurrent extraction unit. The antiradical and antioxidant activities of the OMWW extract as well as pure phenolic compounds identified in this extract were evaluated. Results showed that pure hydroxytyrosol and 3,4-dihydroxyphenyl acetic acid had the highest radical-scavenging effects on 1,1-diphenyl-2-picrylhydrazyl radical and the highest antioxidant activities using the beta-carotene linoleate model system. The effect of addition of individual phenolic compounds and OMWW extract to refined olive and husk oils was compared with that of control, BHA and BHT at 50 C. Unexpectedly, 3,4-dihydroxyphenyl acetic acid had the highest protective effect against oil oxidation. Oils with added 3,4-dihydroxyphenyl acetic acid had lower PV than oils with added hydroxytyrosol, the most studied powerful antioxidant. Moreover, the addition of OMWW extract, at 500 ppm, resulted in lower PV values than BHA, p-hydroxyphenylacetic acid, tyrosol on the control. The results suggested that 3,4-dihydroxyphenyl acetic acid, hydroxytyrosol and OMWW extract possess useful antioxidant properties and may be used as alternatives in the search for natural replacement of synthetic antioxidant food additives. (c) 2004 Elsevier Ltd. All rights reserved.