An Australian scientific review, part of a monograph on extra virgin olive oil, shows how it is ideal for cooking and even frying. (1)
Extra virgin olive oil, nutraceuticals and cooking functionality
Extra virgin olive oil (EVOO) can be qualified as a superfood because of its nutritional and health properties. In fact, monounsaturated fatty acids such asoleic acid, vitamin E, polyphenols and phenolic compounds, phytosterols and other phytocompounds help to prevent and/or mitigate various diseases, as well as promote body functions and strengthen the immune system. (2)
Cooking allows many of these bioactive compounds to be transferred into foods, thereby increasing their nutritional and health properties (even if already present as in the case of vegetables). Provided the smoke point is not exceeded (see next paragraph) and in proportion to the sweetness of the heat treatment. In cooking, EVOO accelerates heat transfer and inhibits food from sticking to the surface. As well as imparting distinctive scents, aromas and colors.
Heat and smoke point
The heat to which an oil is subjected in cooking accelerates its oxidation. Substances harmful to health such as free fatty acids, trans and hydrogenated fatty acids can also be formed, in addition to unpleasant volatile compounds.
The smoke point is the temperature at which the oil begins to emit a bluish smoke due to the evaporation of various breakdown products. This parameter is useful in the kitchen to understand excess temperature, in the absence of a thermostat.
Suitability for cooking of various types of oil
The suitability of various oils for cooking and their stability-that is, their ability to tolerate high temperatures without deteriorating and becoming hazardous to health-is now measured in their ability to resist the formation of polar compounds. And extra virgin olive oil proves to be excellent in this respect, as the antioxidants it contains significantly reduce the formation of polar compounds.
The classical idea of referring to the cooking point to determine an oil’s resistance to heat has been vice versa, for two reasons:
– the cooking point is lowered during heating, particularly in oils high in polyunsaturated fatty acids (PUFAs. e.g., canola, corn, soybean),
– smoke is caused by the evaporation of a small fraction of the free fatty acids, which constitute less than 1 percent of the oil. Therefore, it is not enough to measure overall fat deterioration.
Methods of cooking. The winning recipe
Cooking methods affect the integrity of the oil. Although the formation of toxic compounds (e.g., acrolein) is hindered by the presence in EVOO of antioxidants and oleic acid, the following should be considered:
– frying can be done by immersion (e.g., deep fryers), or in a frying pan, where the amount of oil used is generally less. In the latter case, the oil is more susceptible to oxidation (due to greater contact with the surface and thus heat),
– the essential winning recipe, as seen (see. paragraph ‘Stir-fry and healthy sauces, the winning recipe‘, in the previous article), is to mix oil with water, in equal or slightly greater amounts, to be cooked in a pan over low heat.
Comparing oils
A previous study conducted by the same authors of the research under review showed that EVOO (extra virgin olive oil) was the most stable among the different oils tested with identical heat treatments, in a frying pan and in a deep fryer. (3)
EVOO is therefore strongly recommended for use in frying, replacing refined seed oils which among other things:
– are often packaged in transparent or otherwise clear PET bottles and are therefore even more vulnerable to photosensitive oxidation,
– may contain carcinogenic and genotoxic process contaminants (GE and 3-MCPD, fatty acid glycidyl esters, and 3-monochloropropanediol), with respect to which the European Commission has failed to dutifully manage the risk that emerged as a result of EFSA 3.5.16 assessment.
Optimal parameters
The optimal parameters for oils intended for cooking, in order to ensure better stability and health functionality, are expressed as follows:
– Initial free acidity, < 0.2% (w/w expressed as oleic acid),
– peroxide value, < 5.0 mEq/kg,
– Total polar compounds after 8 hours of heating at 180 °C, < 25%,
– Induction time in the Rancimat (accelerated shelf-life test), > 15 hours,
– p-Anisidine value(marker of secondary lipid oxidation) after 8 hours at 180 °C, < 70. (4)
Dario Dongo and Andrea Adelmo Della Penna
Notes
(1) Ana Florencia de Alzaa, Claudia Guillaume, Leandro Ravetti. (2021). Cooking with Extra Virgin Olive Oil. Intechopen, https://doi.org/10.5772/intechopen.97165
(2) Dario Dongo and Alessandra Mei. Coronavirus, extra virgin olive oil and the immune system. GIFT(Great Italian Food Trade). 9.4.20, https://www.greatitalianfoodtrade.it/salute/coronavirus-olio-extravergine-d-oliva-e-sistema-immunitario
(3) Ana Florencia de Alzaa, Claudia Guillaume, Leandro Ravetti. (2018). Evaluation of Chemical and Physical Changes in Different Commercial Oils during Heating. ACTA Scientific Nutritional Health 2(6):2-11
(4) Eyres et al. (2019). Exploding the myth – NZ Extra Virgin Olive Oil is an ideal frying oil. Food New Zealand 19(3):12-16
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
Graduated in Food Technologies and Biotechnologies, qualified food technologist, he follows the research and development area. With particular regard to European research projects (in Horizon 2020, PRIMA) where the FARE division of WIISE Srl, a benefit company, participates.
