Changes in the content of bioactive substances and antioxidant properties of selected vegetables after heat treatment

In the present study, the effects of heat treatment (boiling in water, steaming) on changes in the content of vitamin C, total polyphenols, and changes in antioxidant activity in garlic, onion, pepper, potatoes and tomatoes were investigated. In the obtained extracts of the mentioned raw and heat-treated vegetables, the content of vitamin C, the content of total polyphenols and antioxidant activity (ABTS, DPPH, FRAP) were determined. The obtained results showed that the content of vitamin C, as well as the content of total polyphenols in the monitored vegetables after boiling in water, was significantly reduced (p < 0.05) compared to the content of these bioactive substances in raw vegetables. A slight decrease in vitamin C and total polyphenol content was recorded in the steamed samples. This decrease was not statistically significant for all these crops. Determination of antioxidant activity again showed a more significant decrease in antioxidant activity values (p < 0.05) after boiling in water than after steaming. The heat treatment has a significant impact on the change in the content of bioactive substances in the analyzed vegetables. Based on our achieved results, steaming appears to be a gentler way in terms of preserving natural antioxidants.