The presence of oxidizing enzyme activities in virgin olive oil

Samples of Greek virgin olive oils were examined for the presence of proteins and oxidative enzyme activities. All oil samples tested contained detectable amounts of protein, as well as lipoxygenase and polyphenol oxidase activities. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and size‐exclusion chromatography of olive oil extracts revealed the presence of low‐molecular‐mass (10–40 kDa) silver‐staining and ultraviolet‐absorbing components, respectively. Both lipoxygenase and polyphenol oxidase catalytic activities were heat‐ and protease‐sensitive, and they expressed Michaelis‐Menten kinetics.