According to an article published recently in the prestigious American magazine Food Chemistry, a study carried out by the University of Granada has demonstrated that vegetables retain more of their nutrients when they are sautéed in olive oil than when they are boiled.
The results of this study form part of the doctoral thesis by Jessica de Pilar Ramírez. It was researched under the supervision of the university's professors, Cristina Samaniego Sánchez, Marina Villalón Mir and Herminia López-García de la Serrana in the Department of Nutritional Bromatology, Faculty of Pharmacology, University of Granada, with the support of the programme PROMEP/SEP, Mexico UD6-596.
The aim of the study was to determine which cooking method did most to improve the antioxidant capacity and phenols found in some of the vegetables typically present in the Mediterranean diet (potato, pumpkin, tomato and aubergine).
The researchers designed an experiment in which they cooked 120g portions of of diced potatoes, pumpkin, tomato and aubergine with their skin and seeds removed. The vegetables were sautéed in extra virgin olive oil, or boiled in water or a mixture of water and extra virgin olive oil.
The vegetables were then tested for levels of moisture, fat, dry matter and phenols, as well as the antioxidant capacity of the samples for each cooking method.
The results showed that the use of extra virgin olive oil to fry vegetables increases their fat content and reduces their moistness, due to the transfer of phenols from the oil to the vegetables. This results in an increase in the quantity of phenols found in the food, while in the other cooking methods no such rise is observed.
Therefore, the study confirms that shallow frying in olive oil is the method which provides the best results in terms of phenolic substances, and hence antioxidants, although it includes an increase in calories due to the absorption of the oil. This refutes the commonly-held belief that vegetables are healthier and retain their nutrients better when they are boiled.