Effects of direct-electric-current on secondary plant compounds and antioxidant activity in harvested tomato fruits (Solanum lycopersicon L.)

The effects of direct-electric-current (DC) on secondary plant compounds and antioxidant activity in harvested tomato fruits were investigated. A new technology was developed to supply DC to the tomatoes. Different intensities of DC (100-500 mA) with varied application times (15-60 min) were applied during postharvest. Almost all DC treatments significantly affected the secondary metabolism, resulting in an accumulation of carotenoids, phenolic compounds, and antioxidant activity in tomatoes. In the present study, optimal DC treatments were found in order to obtain the highest content of all investigated secondary plant compounds. After an adaptation time (AT) of 2 h, the maximum contents of lycopene (122.4%), ß-carotene (140.4%), total phenol (120.0%), and antioxidant activity (126.5%) were attained with a DC treatment of 500 mA for 15 min. The results changed after an adaptation time of 24 h (AT 24 h), where the highest contents of lycopene (128.7%), ß-carotene (129.6%), total phenol (113.6%), and antioxidant activity (120.9%) were obtained using the same DC treatment (500 mA), but with an application time of 30 min. Therefore, the application of DC in harvested tomato fruits may be appropriate to improve the health-promoting properties of tomatoes.