Abstract: Response surface methodology (RSM) was applied to optimize the ultrasonic-assisted extraction conditions of polyphenols from fresh Olea europaea L.fruit.The contents of polyphenols in eight O.europaea varieties with five maturities were measured.Based on the single factor experiments,ultrasonic time,ultrasonic temperature and solid-liquid ratio were selected for Box-Behnken central composite design.By means of quadratic polynomial regression,the optimal extraction conditions were obtained as follows:solid-liquid ratio was 1:22 g/mL,ultrasonic time was 30 min,ultrasonic temperature was 47 ℃.Under these conditions,the average extraction yield was 6.8145 mg/g,with relative error of 1.35%.The result indicated that the optimized process using response surface methodology was reliable and feasible.Due to the difference of O.europaea cultivars,the polyphenols contents was different.The results showed that the polyphenols contents were highest in the first maturity,then decreased with the increasing of ripening stages,bottomed at the third maturity,and followed by another slightly increasing,finally kept steady.

Key words: Olea europaea L., polyphenols, response surface methodology, ultrasonic-assisted extraction, ripening stage