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The antioxidants of EVOO retain their beneficial properties when used in fried foods

The antioxidants of EVOO retain their beneficial properties when used in fried foods

2017/03/05 - Researchers from the Innovation Group in Chemical Analysis at the University of Jaén (UJA), in collaboration with the Laboratory of Bromatology and Hydrology of the Faculty of Pharmacy of the University of Porto, have shown that extra virgin olive oil presents greater resistance to the frying process than other oils available on the market.

After a comparison with other vegetable fats, experts have pointed out that the high number of antioxidants present in EVOO contributes greatly to degrade less and slower than other oils, in addition to being the most stable and producing fewer toxic compounds.

According to the Fundación Descubre, experts have reached these results after comparing the process of thermal oxidation of some of the most recommended oils in fried foods. In particular, they have analyzed extra virgin olive oil, the most used in the Mediterranean countries; peanut oil, used in Portuguese school canteens; and canola, a type of rapeseed oil, very common in some Central and Eastern European countries.

In order to carry out the investigation, the oils were kept hot for many hours while fryings were carried out at different times. After each frying, the oils were analyzed considering the substances formed and the components that could be harmful to human health. Thus, they identified more than 30 toxic compounds derived from the thermal stress to which the oils were subjected when frying.

In the article published in the Journal of the American Oil Chemists' Society entitled "Comparative Fingerprint Changes of Toxic Volatiles in Low PUFA Vegetable Oils Under Deep-Frying" researchers have shown that the benefits of extra virgin olive oil compared to other used are also due to a lower percentage of polyunsaturated fatty acids, such as omega 3 and a higher percentage of monounsaturated fatty acids, such as oleic (omega 9), one of its main components.

The Foundation has explained that, although all the oils studied have a low content of polyunsaturated fatty acids, they have observed that EVOO produces fewer toxic compounds when fried and takes longer to appear compared to peanut and canola due to the high content of antioxidant compounds. These help the olive oil to undergo a slower degradation than the others.

Therefore, these investigations have confirmed that extra virgin olive oil is the most suitable for its stability after several hours at high temperatures. "For the consumer it is preferable to use oil during the eight hours after its use, since there is a high prevalence of toxic products of thermal oxidation that are not observed before. In addition, extra virgin olive oil still has a good nutritional value and consequently, there is a greater use by the human body," says the researcher of the University of Jaén Lucía Molina, one of the authors of the article.

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The project has included the study of the nature and concentration of those compounds that are altered or appear during the frying process, especially those that have some implication detrimental to human health, such as volatile aldehydes.

In addition, the study provides detailed information on the volatile compounds that originate during frying as a result of the thermal degradation of the oils, which provides a better understanding of the chemical reactions that develop in the process.

Thus, these substances can be established as quality indicators to control and ensure their nutritional value and useful life.

It must be noted that the tests consisted on frying potatoes in the three oils for six minutes, every 30 minutes and for 30 hours. Each time a frying was carried out, a sample of the oil was taken and the volatile compounds were extracted and analyzed.

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