EVALUATION OF ANTIOXIDANT ACTIVITY OF SOME TROPICAL FRUIT PEEL EXTRACTS: EXTRACTION CONDITIONS OPTIMIZATION OF RAMBUTAN PEEL EXTRACT
This work reports a study on evaluation of antioxidant activity of some tropical fruit peel extracts and optimization of extraction conditions for recovery of antioxidants from the selected fruit peel. Due to the extensively growing of many fruit processing industries, the fruit peels are often removed as a waste residues. Hence, the research has shift to focus on fruit residues as potential source of natural antioxidant replacing the synthetic one which may poses several side effects. Extraction was done on selected tropical fruits peels including rambutan, banana, mangosteen, logan to evaluate their antioxidant activity. Rambutan with ethanol extract possess highest antioxidant activity which is 77.21 0.17 as compared to longan (73.24 0.11% mangosteen (46.97 0.29) and banana (41.65 0.22) for ethanolic extraction. Thus, rambutan was chosen to be continued with screening and optimization process. Single factor experiment using the one factor at a time (OFAT) method was done to study the effect of solvent to solid ratio (300:10 to 300:50 mL/g) extraction temperature (78 to 85 oC) and extraction time (120 to 360 minutes) Next, central composite rotatable design (CCRD) coupled with Response Surface Methodology (RSM) was applied to optimize the extraction conditions on the antioxidant activity of rambutan peels. From the result, the highest antioxidant activity of about 96.12 0.013 was found at optimum conditions of solvent to solid ratio, 300:33 (mL/g) extraction temperature, 81oC and extraction time, 262.95 minutes. Based on statistical analysis, the extraction temperature was the most significant (p<0.0001) parameter condition affecting antioxidant activity and R2 value of 0.9810 denoted that the model developed was adequate in optimizing the extraction conditions of antioxidant properties from rambutan peels.