Tomato (Lycopersicon esculentum) is one of the rich sources of antioxidants, mainly, lycopene which is known to be associated with decreased risks of chronic diseases. However, cooking influences the antioxidant properties of vegetables. Therefore, this study aimed to determine the effect of three cooking methods on the antioxidant properties of tomato. The conditions of the cooking methods of tomato were boiling at 100 ºC for 6 min, microwave cooking at 560W for 40 sec and stir-frying at 230 ºC for 4.5 min. Ethanol (70 %, v/v) was used to extract the antioxidant properties (such as phenolics, flavonoid and other antioxidant compounds) of tomato. These antioxidant properties were determined by using total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity and DPPH radical scavenging activity analysis. Results indicated that cooking has significant influences on the antioxidant properties of tomato. Boiling did not have significant changes in the TPC, however microwave cooking and stir-frying caused significant losses compared to fresh tomato. Stir-fried tomato had significantly the lowest TPC. All three cooking methods caused significant losses in TFC, however the losses are less significant during boiling compared to microwave cooking and stir-frying. Significantly higher antioxidant capacity was observed in microwave cooked tomato than fresh and other cooked tomatoes. The highest antioxidant activity was observed in microwave cooked tomato followed by stir-fried and fresh tomatoes.

Purpose: Bitter gourd (Mormodica charantia) is a widely cultivated vegetable crop in Jaffna. It is well-known to possess medicinal properties, mainly because of its antioxidant properties. Changes in the antioxidant properties of vegetables during different cooking methods have an influence on dietary nutrition. Therefore, this study is aimed at determining the effect of three cooking methods on the antioxidant properties of bitter gourd. Research Method: Fresh bitter gourds were cut into small pieces and subjected to three different cooking methods (boiling, microwave cooking and stir-frying). The conditions of the cooking methods were; boiling at 100ºC for 14 min, microwave cooking at 560W for 4 min and stir-frying at 230ºC for 15 min. Ethanol (70 %, v/v) was used to extract the antioxidants from fresh and cooked samples and antioxidant properties were determined as total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity and DPPH radical scavenging activity. Results were analyzed using oneway analysis of variance using Statistical Analysis System (SAS 9.1). Findings: TPC, TFC, antioxidant capacity and DPPH radical scavenging activity (IC 50 value) of fresh bitter gourd were 27.47±1.52 mg gallic acid equivalent/g dry matter, 19.36±2.01 mg catechin equivalent/g dry matter, 103.55±3.60 mg ascorbic acid equivalent/g dry matter and 0.210±0.008 mg/ mL respectively. Compared to the antioxidant properties of fresh bitter gourd, boiling has significantly (p<0.05) increased TPC (by 48.63%) and TFC (by 42.77%) while, antioxidant capacity was reduced (by 17.84%). However, TPC, TFC, and antioxidant capacity of bitter gourd were reduced by 38.70%, 40.13% and 23.55%, respectively, after microwave cooking and 77.94%, 75.88% and 67.77%, respectively, after stir-frying. Thus, it can be concluded that boiling found to be the better method than other two methods to retain antioxidant properties of the bitter gourd. Originality/ Value: This study could be useful to create the awareness among the people on different cooking methods to retain as much of the antioxidant as possible in order to get benefited by the consumption of bitter gourd.