OLIVE OILS AND HEALTH 84 5.4. Frying Frying causes very complex chemical changes, for instance, oxidation, polymerisation, and hydrolysis, in all oils. Various compounds are released, some toxic, according to the type of oil, frying time, and food. The reactions can be ameliorated if the oils have antioxidant compounds. As previously mentioned, such changes occur to a lesser degree in EVOO thus reducing its toxicity. When frying, polyphenols prevent fatty acid oxidation. Frying meat produces polycyclic aromatic amines whose long-term intake is associated with an increase of cancer incidence. Generation of these procarcinogen components is reduced when frying with EVOO. When frying potatoes, a Maillard reaction occurs leading not only to unpleasant colour changes, but also to the release of harmful compounds such as acrylamide whose long-term consumption could be neurotoxic. Fried potatoes are of similar colour and with less acrylamide when a high polyphenol content EVOO is employed as the polyphenols inhibit harmful reactions. Although several studies have shown that when frying EVOO is more protective than other vegetable fats, there is a lack of human intervention studies evaluating the benefits of cooking with virgin olive oil in comparison with other oils or fats. 5.5. Extra virgin olive oil for vegetables When vegetables are cooked with EVOO, a transfer of antioxidant compounds occurs and the vegetables’ antioxidant capacity increases (Figure 5.3). In contrast, when boiling vegetables in water, even with EVOO added, a transfer of nutrients from the vegetables to the water takes place thus reducing their antioxidant content (Figure 5.3). Figure 5.3. Migration of antioxidants. EVOO: extra virgin olive oil. EEVO for vegetables oleocanthal ferulic acid
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