Fried foods are widely regarded to be terrible for your health. However, researchers recently found that frying raw vegetables in extra virgin olive oil was the cooking method that increased the amount of phenolic compounds present in raw vegetables the most. Phenolic compounds ward off chronic degenerative diseases, such as cancer, age-related vision loss, and diabetes. The cooking method also increased the number of antioxidants.
The University of Grenada researchers used vegetables found in the Mediterranean diet, such as potato, pumpkin, tomato, and eggplant. The Mediterranean diet is high in both vegetables and extra virgin olive oil. People from the region have longer life expectancies compared to those in North America and Northern Europe. They additionally have lower risks of heart disease, high blood pressure, and stroke.
The researchers tested the vegetables in seedless and skinless cubes. The food was fried and sautéed in extra virgin olive oil, boiled in water, and boiled in a mix of water and extra virgin olive oil. The cooked vegetables were also compared against raw vegetables. The researchers measured moisture, fat, dry matter, phenols and antioxidants.
The data showed that heat transfer done through extra virgin olive oil increased the number of phenolic compounds in the vegetables. Heat transfer done through water did not show the same results. This is due to the fact that extra virgin olive oil has its own phenols and they were transferred through heat into the vegetables. Unlike other cooking methods, frying the vegetables in extra virgin olive oil also increased fat content and reduced moisture.
"Therefore, we can confirm that frying is the method that produces the greatest associated increases in the phenolic fraction, which means an improvement in the cooking process although it increases the energy density by means of the absorbed oil", said co-author Christina Samaniego. "When the phenolic content of the raw vegetable is high, the total content of phenols is increased even more if extra virgin olive oil is used in the process, and boiling doesn't affect the final concentration."
“Therefore, we must stress that frying and sautéing conserve and enhance the phenolic composition,” Samaniego said. “Hydrothermal cooking methods can be recommended when the food is consumed together with the cooking water, as the addition of extra virgin olive oil improves the phenolic profile and compensates for the deficiencies of the raw food.”
The research was published in the Food Chemistry magazine.
Sources: University of Grenada press release via EurekAlert!, Medical Daily, Medical News Today