Extracts of olive polyphenols improve lipid stability in cooked beef and pork: Contribution of individual phenolics to the antioxidant activity of the extract

Crude polyphenol extracts (50 or 100 mg gallic acid equivalents (GAE)/kg meat) from the waste waters of olive oil pomace reduced the formation of 2-thiobarbituric reactive substances (TBARS) in pre-cooked beef (63–83%) and pork (47–66%). When compared with other antioxidants, the ranking of activities were: tea ≫ olive > wine. The olive extract contained hydroxy-tyrosol (70.6%), tyrosol (17.5%), caffeic acid (9.5%), p-coumaric acid (1.9%) and vanillic acid (0.3%). Relationship between polyphenol composition and antioxidant activity of a blend containing oleuropein, tyrosol, hydroxy-tyrosol, quercetin, rutin and caffeic, vanillic and coumaric acids was described by a first order polynomial model. Quercetin, hydroxy-tyrosol, caffeic acid and oleuropein had the highest contributions to the linear term followed by rutin and tyrosol. We detected the strongest positive synergism between tyrosol and quercetin, hydroxy-tyrosol, oleuropein and to a lesser degree with caffeic acid whilst the effect of vanillic and coumaric acids were not significant.