OPTIMISATION OF THE EXTRACTION OF FLAVONOIDS FROM APPLES USING RESPONSE SURFACE METHODOLOGY

The ultrasound-assisted extraction of flavonoids from apple samples was modelled using response surface methodology. A three-level-three-factor central composite design using the response surface methodology (RSM) was employed to optimise three extraction variables, including temperature, extraction time and ultrasonic power, for the achievement of the highest extraction yield of the flavonoids from lyophilised apple samples. The optimised extraction conditions were 44.61[degrees]C, an extraction time of 26.90 min, and ultrasonic power 480 W. The experimental yield of flavonoids was 6.58 mg [g.sup.-1] expressed as rutin equivalent, which was close to the predicted yield (6.69 mg [g.sup.-1]). Optimised extraction conditions were applied for the analysis of apple samples of six cultivars. Keywords: apple, central composite design, flavonoids, HPLC, response surface methodology, ultrasonic extraction