Total phenolic content and antioxidant activity of apple pomace aqueous extract: effect of time, temperature and water to pomace ratio

This study aimed to evaluate the effects of extraction time, extraction temperature and water to pomace ratio on the total phenolic content and antioxidant activity of apple pomace aqueous extracts. Pomace was extracted using water (20-90°C) for 5-60 min. The extracts were evaluated for their total phenolic content (Folin Ciocalteu assay) and antioxidant activity (DPPH, FRAP and ABTS assays). A methanol extract of the pomace was used as control. It was found that water to pomace ratio (p < 0.001), extraction temperature (p < 0.001) and time (p < 0.001) were significant factors in extracting the polyphenolics from apple pomace, with the optimum extraction conditions utilising water to pomace ratio of 20:1 at 90°C for 15 min yielding the most polyphenolic compounds (1148 μg g-1 fresh pomace Gallic Acid Equivalents). These results indicated that water was a good solvent for extracting polyphenolics from apple pomace, however, as compared to the methanol extract (control), the aqueous extracts had lower total phenolic content (63%) and antioxidant activity (73-80%).