Researchers from Spain and Brazil have found that cooking vegetables with extra virgin olive oil can improve the extractability of their polyphenols, increasing the amount of the compound that is absorbed by the oil.
The study examined the inner workings of the traditional methods of Mediterranean cooking, attempting to shed light on how extra virgin olive oil interacts with the ingredients of the local cuisines. Along with polyphenols, various other bioactive compounds from the vegetables were also found to be absorbed by the oil when cooked.
The researchers focused on the sofrito method, a popular Mediterranean cooking technique for preparing a light sauce with tomato, onion and garlic. Sofrito reportedly contains 40 different phenolic compounds and a high content of carotenoids, while its consumption is associated with reduced cardiovascular risk and insulin sensitivity.
After the cooking process, an analysis of the olive oil showed that it was infused with polyphenols from the vegetables in the sofrito sauce; specifically with naringenin, ferulic acid, quercetin and Z-isomer carotenoids, none of which are typical compounds of extra virgin olive oil.
The migration of bioactive compounds such as polyphenols and carotenoids from the tomato to the olive oil also explained the findings of previous work of the researchers, which had concluded that the specific type of sauce demonstrated increased anti-inflammatory properties.
“In intervention nutritional studies we have observed that polyphenols from tomatoes were better absorbed when the tomato was cooked as a sauce with extra virgin olive oil,” Rosa Maria Lamuela-Raventos, a food science professor at the University of Barcelona and a researcher at Ciberobn (the research center for obesity and nutrition of Spain).
“For this reason, we wanted to evaluate why this was happening, so we performed an in vitro assay where we separated sofrito in three fractions or parts: solid (insoluble part), water fraction and oil fraction,” she added. “In this paper we observed that some of the polyphenols from the tomato, onion and garlic were moving to the oil fraction, being more bio-accessible, so easier to be absorbed.”
Additionally, the researchers noticed that the polyphenols in the olive oil were also reduced, by degrading or by migrating to the food matrix.
“There is an exchange of polyphenols during cooking, some more apolar from vegetables go to the oil fraction, while some from the oil are absorbed by the vegetables,” Lamuela-Raventos, who was also the main author of the study, said. “However, the temperature is important while cooking, because high temperatures over 100 degrees Celsius (212 degrees Fahrenheit) oxidized polyphenols.”Having used science for years to assess the qualities of different edibles and food ingredients, Lamuela-Raventos regards the Mediterranean diet as one of the healthiest.
“[The Mediterranean diet] is one of the healthiest diets in the world,” she said. “As a scientist, I observe that the results with the traditional Mediterranean foods and dishes – such as extra virgin olive oil, sofrito, wine and more – give really very good results in intervention nutritional studies.”
However, science and good health are not the only parameters to be taken under consideration when it comes to the Mediterranean diet, Lamuela-Raventos added.
“As a consumer, I try to follow a Mediterranean diet not only for health reasons but also because of the way cooking and eating habits with family and friends are good not only for health but also for sociability and happiness,” she said.
“We are continuing our research about cooking with extra virgin olive oil with other food rich in proteins such as chicken or in carbohydrates such as potatoes,” Lamuela-Raventos added. “We want to evaluate if extra virgin olive oil polyphenols are absorbed in these foods while cooking.”
The health effects of the Mediterranean diet have been difficult to reproduce in non-Mediterranean populations, the researchers noted, in all likelihood due to the different cooking techniques used.
The researchers’ work established that, apart from consuming the ingredients and staple foods of the regime, traditional cooking from the Mediterranean can also play an important role in taking full advantage of the benefits of the Mediterranean diet.