Comparisons on the antioxidant properties of fresh, freeze-dried and hot-air-dried tomatoes

In this study, two varieties of tomatoes (Lycopersicon esculentum Mill.), “I-Tien-Hung (ITH)” and “Sheng-Neu (SN)”, were used to study the effects of different drying processes, freeze-dried (FD) and hot-air-dried (AD), on the antioxidant properties of tomatoes. In the quantitative analysis of antioxidative components, fresh SN samples had the highest amount of ascorbic acid but the lowest amount of total flavonoids. AD-ITH and AD-SN had the highest content of total phenolics, and AD-SN contained the highest amount of lycopene. In the analysis of reducing power, methanolic extract (ME) from FD tomato gave the highest reducing power while the butylated hydroxyanisole (BHA) and α-tocopherol had the lowest. For the ferrous ion chelating power, MEs from AD tomatoes had the highest values while BHA and α-tocopherol exhibited no ferrous ion chelating power. In the analysis of 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging ability, all the tomato samples exhibited the same activity as that of BHA.