Effect of drying and cooking methods on antioxidant properties of bitter gourd (Momordica charantia)

The effect of various cooking methods (stir frying, deep frying, boiling, steaming and microwaving) and oven-drying at three different temperatures (40, 50 and 60 °C) on antioxidant properties of bitter gourd were evaluated. Total phenolic content (TPC) was measured using Folin-Ciocalteu method while the antioxidant activity was evaluated using methanol solution of DPPH and ferric reducing potential assay using FRAP reagents. All analyses were conducted using the microplate reader spectrophotometer. The results indicated that deep frying had the highest TPC at 98.18 mg/100 g GAE, followed by microwave cooking (25.63 mg/100 g GAE). The TPC for deep-fried samples was significantly different (p 0.05) from the other cooking methods. However, microwave cooked samples have significantly (p 0.05) higher percentage of DPPH radical scavenging activity (88.54%) and FRAP (65.85 μmol/g FE) compared to oven-dried, boiling or deep frying. For oven-drying, bitter gourd dried at 40 °C retained the highest antioxidant activities compared to samples dried at 50 or 60 °C. Thus, the best drying temperature to retain antioxidant properties in bitter gourd is at 40 °C while the best cooking method is either microwave or deep fried