Effects of heat treatments on the physicochemical and antioxidant properties of yellow plum tomato (Solanum lycopersicum L., var. Blondkopfchen )

The thermal processing of tomato ( Solanum lycopersicum L. ), both at home and commercially, is key for obtaining derivatives, such as preserves, sauces, pastes, and purees, consumed worldwide. Therefore, in this study, the effects of different heat treatments, such as frying, blanching, and cooking, on the physicochemical parameters and antioxidant properties of yellow plum tomato ( S. lycopersicum L., var. Blondkopfchen ) were evaluated. The conditions used were frying in vegetable oil (150 ± 5 °C, 3 min), blanching in water (90 ± 2 °C, 5 min), and cooking in water (95 ± 2 °C, 10 min) compared to fresh fruit. Heat treatments showed significant differences ( p < 0.05) in physicochemical and antioxidant properties compared to fresh tomatoes. Regarding color, increases in the yellowness index were observed in all heat treatments. Frying resulted in the highest total carotenoid content (3.35 mg/100 g), and antioxidant activity (AA) [15.52 mmol Fe + 2 /100 g and 46.59% 2,2-diphenyl-1-picrylhydrazyl (DPPH)] compared to the fresh sample, which had values of 2.07 mg/100 g, 9.63 mmol Fe + 2 /100 g, and 32.24% DPPH, respectively. Blanching resulted in the lowest loss of total phenolic content (8.34 mg GAE/100 g) compared to the other methods, while cooking resulted in the lowest loss of vitamin C (48.58 mg/100 g) compared to the other methods. It can be concluded that frying is the best treatment for increasing the ash, ether extract, total carotenoid content, and AA content in plum tomatoes compared to the other methods. Blanching and cooking allow for a higher concentration of preservation of total phenolic compounds and vitamin C compared to frying. This information is relevant for optimizing production processes and promoting the use of this little studied variety in the food industry.