A team of scientists from the University of Granada (Spain) has shown that vegetables fried with olive oil improve their healthy properties with respect to their antioxidant capacity and the content of phenolic compounds , which prevent cancer, diabetes or macular degeneration . The work has been published in the journal Food Chemistry .
The fresh vegetables consumed in the Mediterranean diet are also characterized by being accompanied by a frequent consumption of extra virgin olive oil. Both vegetables and olive oil are an important source of phenols or phenolic compounds already associated by many previous studies with the prevention of chronic degenerative diseases.
To test the effect of culinary techniques on vegetables, the researchers conducted an experiment with potato, pumpkin, tomato, and eggplant . All of them, without skin or seeds, were prepared in different ways: fried and sautéed with extra virgin olive oil, boiled with water or cooked with a mixture of olive oil and water.
The cooked foods were examined by different methods such as the determination by high efficiency liquid chromatography of the content of phenolic compounds in vegetables. The results showed that the use of extra virgin olive oil for frying, not only did not modify the total phenols, but also increased the fat content and reduced the humidity of the vegetables , something that did not happen with the rest of culinary processes.
“When comparing the content of total phenols with respect to fresh vegetables, we find both increases and reductions according to the applied technique. Oil as a heat transfer medium increases the content of phenolic compounds in vegetables, compared to other culinary techniques such as boiling where heat transfer occurs through water ”, explains Cristina Samaniego, co-author of the study.
The cause of this improvement in the properties of vegetables is due to the fact that olive oil transfers phenols to them, enriching them with compounds that are not found naturally in fresh vegetables .
“When the phenol content of raw vegetables is high, the total phenol content increases even more if EVOO is included during processing and the application of boil treatments does not affect the final concentrations. We must therefore emphasize that frying and sautéing preserve and enrich the phenolic composition ”, clarifies Samaniego.
