Effects of different drying methods on the total phenolics, antioxidant properties, and functional properties of apple pomace

Effects of different drying methods on the total phenolics, antioxidant properties, and functional properties of apple pomace Apple pomace was dried using three different drying methods: freeze drying at air temperature of 20°C, drum drying at drum temperature of 140°C, and cabinet drying at air temperatures of 60 °C, 80 °C, and 100 °C. The dried samples were measured using Hunter Color CIE L*,a*, and b* values. The total color difference (DeltaE) of apple pomace was affected by the drying temperature and the type of drying method. The freeze dried pomace was significantly higher in L* value compared to all of the other samples, whereas cabinet drying at 100°C showed the highest average color a* and b* values. The dried apple pomace was analyzed for total phenolics and antioxidant capacity using ORAC, and DPPH. The total phenolics of dried pomace, with the highest value ( 3.05 mg GAE/g) observed in freeze dried and the lowest (1.85 mg GAE/g). In the cabinet dried pomace, total phenolics decreased gradually as the process temperature was increased from 60 °C to 80 °C or 100 °C. Freeze dried pomace had the highest antioxidant activity as exhibited by ORAC and DPPH results, 350.27 and 278.8 &mgr;mol TE/g, db, respectively. Drum drying of pomace at 140 °C reduced activity to 158.06 and 216.45 &mgr;mol TE/g, db, by ORAC and DPPH assays, respectively. Cabinet drying of pomace resulted in lower antioxidant values as drying temperature increased from 60 °C to 80 °C or 100 °C.