Physicochemical Properties and Antioxidant Activity of Commercial Tomato Ketchup

Abstract

The objective of this study was to investigate the physicochemical properties and antioxidant activities of seven (A, B, C, D, E, F, G) commercial ketchups marketed in Korea. The 70% ethanol extracts were prepared and evaluated for total phenolic content, DPPH and ABTS radical scavenging activities, and metal chelating effect. pH ranged from 3.64 to 3.94, and soluble solid and reducing sugar contents of samples were 2.21~3.51oBrix and 4.78~13.45%, respectively. Salinity of samples was in the range of 1.79 to 3.21%, and sample G showed the lowest salinity. The lightness, redness, and yellowness of the Hunter color system of samples were 15.42~19.94, 18.55~23.98, and 20.87~24.34, respectively. The phenolic contents ranged from 1.37 to 2.60 mg GAE (gallic acid equivalents)/g, with samples F and G exhibiting the highest contents. Antioxidant activity determined based on DPPH and ABTS radical scavenging activities, and metal chelating effects were 45.10~90.87, 55.35~92.53, and 71.10~92.20%, respectively, at a concentration of 200 mg/mL. Samples A and G showed higher antioxidant activity than other samples. There were positive correlations between phenolic contents and antioxidant activity, suggesting that phenolic compounds are the major contributors to antioxidant activity.