KINETICS OF POLYPHENOL LOSSES AND ANTIOXIDANT ACTIVITY OF EXTRACTS FROM OLIVE CAKE DURING EVAPORATION

Abstract

Polyphenols were extracted from olive cake and then concentrated at 50, 75, and 100 degrees C by the evaporation of extract. Antioxidant activity of total polyphenols in olive cake extract decreased while the concentration of total polyphenols increased during the evaporation of extract at 100 degrees C, but concentration of polyphenols slightly increased while antioxidant activity did not change at 75 degrees C. These results showed that antioxidant activity is not related and estimated with the amount of total polyphenols. Reaction rate for the loss of polyphenols is found zero order at 50 and 75 degrees C with r(2) of 0.99 and at 100 degrees C with r(2) of 0.85. Low r(2) value at 100 degrees C requires the consideration of a different kinetic model to predict the losses of polyhenols at a high temperature of 100 degrees C.