Extra virgin olive oil could protect food during cooking
The extra-virgin Protected Designation of Origin (PDO) olive oil was characterized by reduced levels of oxidation and hydrolysis, and superior amounts of minor antioxidant compounds. The chemical composition of olive oils are important parameters in their predictive behavior along the frying process, but mostly that olive oil is clearly resistant to frying conditions
The use of olive oil showed an important protection of meat and potatoes when compared with other vegetable oils, with sunflower oil samples being oxidised after 60 min of processing at 180 °C. Olive oil samples were not oxidised, independently of the olive oil quality used. Shelf life was longer for extra-virgin olive oil containing samples and this fact was positively correlated with their higher phenolic content. The radical-scavenging activity of extra-virgin olive oil was higher than for other olive oil samples and was also positively correlated with the phenolic content of the oil. Seed oil antioxidants showed little capacity in delaying the oxidative degradation of seed oils and meat processed with them. However, tocopherol content and the identity of tocopherols present in the oil were shown to have a more important role in the oxidative stability of seed oils than the fatty acid composition.
The presence of food showed a protective effect on the oils, with oil samples processed without food showing a higher level of oxidation than the oil samples processed in the presence of food. All polyphenolic components of olive oils decreased in concentration with the thermal treatment and this decrease was dramatic in the presence of food. During processing, two new compounds were found in olive oil samples and their concentration was higher for samples containing a higher initial polyphenolic content. The content in tocopherols was not so dramatically affected by the thermal treatment as was the polyphenolic content. Moreover, a sparing effect of food was, however, observed with the tocopherol content of samples which probably contributes to the better oxidative stability of these samples.
The suitability of different commercial olive oil categories for domestic frying was investigated. Oil samples were taken every 3 h of frying and evaluated for free acidity, peroxide and p-anisidine values, specific extinction coefficients, oxidative stability, fatty acids, vitamin E, β-carotene and total phenols, until the total polar compounds achieved the maximum legal value (25%). All olive oils were fried during more time than the commercial vegetable oil blend taken for comparison (from 24 to 27 h, against 15 h).
The extra-virgin Protected Designation of Origin (PDO) olive oil was characterized by reduced levels of oxidation and hydrolysis, and superior amounts of minor antioxidant compounds. The “olive oil” commercial category behaves similarly, but “Cobrançosa” olive oils performance was slightly worse, and clearly different between years, highlighting the importance of blending different cultivars. The vegetable oil, despite containing significantly higher amounts of vitamin E, was highly susceptible to oxidation under frying conditions when compared to all olive oils.
The results also show that the chemical composition of olive oils, particularly the amount of natural antioxidants, are important parameters in their predictive behavior along the frying process, but mostly that olive oil is clearly resistant to frying conditions, independently to the commercial category chosen.
Lisete Silva, Joana Pinto, Joana Carrola, Fátima Paiva-Martins, Oxidative stability of olive oil after food processing and comparison with other vegetable oils, Food Chemistry, Volume 121, Issue 4, 15 August 2010, Pages 1177-1187