An identikit of olive oil, according to its chemical composition and health benefits.
Chemical composition of olive oil
Olive oil consists of about 98% triglycerides and, for the remaining part, of liposoluble substances (glycerol, phosphatides, pigments, flavor compounds, sterols), mainly present in the mature pulp and almond kernel, dissolved in the oil for natural or technological reasons.
Among the fatty acids that are part of the triglycerides, the most important are:
- oleic acid (C18:1), a monounsaturated omega-9 fat (70-80%);
- linoleic acid (C18:2), a polyunsaturated omega-6 fat (5-10%);
- palmitic acid (C16:0), a saturated fat (7-15%);
- stearic acid (C18:0), a saturated fat (1.5-3.5%);
- α-linolenic acid (C18:3), a polyunsaturated omega-3 fat (0.1-0.9%).
From a nutritional point of view, olive oil contains more oleic acid and less linoleic and linolenic fatty acids than other vegetable oils, that is, more monounsaturated than polyunsaturated fats. This peculiarity renders olive oil more resistant to oxidation because generally, the greater the number of double bonds in the fatty acid, the more unstable and easily broken down by heat, light, and other factors the oil is. Freshly pressed oil, made carefully, without the use of excessive heat, from sound, healthy, freshly picked drupes, normally has a pretty low free fatty acidity (FFA). Extra virgin olive oils have less than 0.8% FFA.
Furthermore, the smoke point of olive oil varies with its quality. High-quality extra virgin olive oils (with low free fatty acids) have a high smoke point, ranging between 400 and 365 °F (204 and 185 °C). They are an excellent choice, but an expensive one. The digestibility of olive oil is not affected when it is heated, even when it is re-used several times for frying.
The flavonoid polyphenols in olive oil are natural antioxidants that contribute to a bitter taste, astringency, and resistance to oxidation. Many other nut and seed oils have no polyphenols. The polyphenol content is determined by many factors including:
- Time of Picking: oil made from green (unripe) olives has more polyphenols than oil made from ripe olives. The polyphenol concentration increases with fruit growth until the olives begin to turn purple and then begins to decrease;
- Extraction Conditions: techniques used to enhance yield, such as heating the paste, adding water, and increasing malaxation time, result in a loss of polyphenols;
- Storage Conditions: the type of containers and the length of storing are critical factors in the oil’s polyphenol content. Oils stored in stainless steel containers or dark glass bottles, in cool conditions, are the best protected against oxidation.
One tablespoon of olive oil provides 8% of RDA for vitamin E.
The gold-green color of olive oil is due to pigments like chlorophyll and carotenoids. The presence of various pigments depends on factors such as the fruit ripeness, the olive cultivar, the soil and climatic conditions, and the extraction and processing procedures. Olives are invariably crushed with some leaves still present, so some of the chlorophyll comes from that source.
Green olives produce a green oil because of the high chlorophyll content. Ripe olives yield a yellow oil because of the carotenoid (yellow-red) pigments. The exact combination and proportions of pigments determine the final color of the oil.
Health benefits of olive oil
The beneficial properties that extra virgin olive oil has on the body are numerous:
- Reduces the percentage of LDL cholesterol
- Reduces the risk of occlusion of the arteries
- Reduces blood pressure
- Reduces blood sugar
- Increases the secretion of bile
- Increases the intake of Vitamins A, D, and E
- Prevents atherosclerosis
- Prevents myocardial infarction