Effect of far-infrared radiation drying of citrus press-cakes on free radical scavenging and antioxidant activities

In this study, far-infrared radiation (FIR) drying was used to convert wet citrus press-cakes (CPCs) into dried form at different temperatures (40, 50, 60, 70, and 80 °C). The dried samples were evaluated for flavonoid composition by HPLC and antioxidant activities by various in vitro assays. Compared with CPCs prepared by freeze drying (FD), all FIR-dried CPCs showed slightly lower extraction yield and total phenolic content, but almost equal total flavonoid contents and antioxidant activities. However, CPCs dried by FIR showed significantly lower drying times. Therefore, FIR drying is effective and economical method. CPCs dried by FIR at 80 °C showed higher antioxidant activities in several assays, and needed very short drying time. Hence, FIR-80 sample was more potential than other FIR-dried samples. The data confirmed that FIR drying is an effective process to convert wet CPCs into dried form which shows strong antioxidant activities.