Courses
Vegetable oils
Lesson I – A comparison of vegetable oils and methods: the effect on chemical composition and nutritional aspects
Triglycerides and fatty acids
All oils are 99.9% made up of triglycerides, but differ considerably in terms of their composition of fatty acids.
As shown above, triglycerides are formed of a molecule of esterified glycerol and three molecules of fatty acids. Fatty acids are formed of a variable number of carbon atoms and are defined as saturated or unsaturated depending on their chemical structure, or due to the absence or presence of double bonds. Unsaturated fatty acids are divided into monounsaturates and polyunsaturates, if they contain only one double bond or more in their carbon chains. If we compare the fatty acid composition of extra-virgin olive oil and that of certain seed oils or those containing tropical fats, (the values are shown in grams per 100 grams of edible part) we see that in extra-virgin olive oil, the fatty acid present in the highest concentration is oleic acid (73.6 g per 100 g).
The other vegetable oils contain a higher quantity of polyunsaturated fatty acids, in particular lineoleic acid and linolenic acid. The latter, known as essential fatty acids, since the human body is not able to produce them, must be included in the diet and are Omega 3 and Omega 6 fatty acids. Extra-virgin olive oil has a balanced proportion of essential fatty acids unlike other vegetable oils, in which linoleic acid is more commonly found than linolenic acid.
Tropical fats such as those obtained from palms or coconuts have a higher content of saturated fatty acids and are solid at room temperature.
Micronutrients and minor compounds
Apart from its fatty acid composition, extra-virgin olive oil also differs from other vegetable oils in terms of its structure of micronutrients and minor compounds.
Over 200 of these compounds have been identified in extra-virgin olive oil, including polyphenols (tyrosol), phytosterols and other molecules which act as antioxidants.
These molecules are the characteristic element of the specific and organoleptic qualities of extra-virgin olive oil, and explain their greater stability in terms of technological treatments and/or cooking compared to other vegetable oils. Antioxidants are compounds which also have a nutritional role, as they are absorbed during digestion and also help to protect against the oxidative stress associated with a number of human diseases.
Why do seed oils have a lower content of antioxidants and vitamins compared to extra-virgin olive oil?
Olive oil has a higher content of antioxidants if compared with other vegetable oils. In fact, total polyphenols in extra-virgin olive oil reach levels of around 800 mg/ml while in other vegetable oils this can correspond to 15 mg/ml. This difference can be attributed to various factors, in particular to the botanical structure. The synthesis of these molecules is higher in plant organs, such as fruits, which are exposed to environmental factors (intense light, high temperatures and contrasts in temperature). The reduced content of antioxidants in vegetable oils compared to extra-virgin olive oil also depends on the technological, chemical and chemical/physical treatments to which the raw materials are subjected during the production of oil.
The oils derived from plant oils are actually produced with longer chains and are subjected to extraction with solvents, deodorization, and subsequent refining which reduces their nutritional quality.
In recent decades, hydrogenated vegetable oils have become commonplace in catering and the food industry. These are obtained by subjecting seed oils or tropical fats to the chemical hydrogenation process.
Numerous epidemiological studies have shown that hydrogenated fats, if assumed in high quantities in the diet, have a damaging effect on health.
Lesson II – Let’s talk about how oils change during cooking →
