Introduction: olive oil
Olive tree: botanical aspects and cultivation
Mature olive composition, nutritional properties
Olive harvest
Olive oil: chemical composition
Olive oil: properties and nutritional characteristics
Preparation of olive oil
Olive oil conservation
Pomace oil
Classification of olive oils, analysis and fraud
Olive oil as a laxative
Olive in herbal medicine - sea buckthorn
Cosmetic use: olive oil - Unsaponifiable with olive oil - Olive leaf extract
Olive oil
The oil is a lipidic substance and like all dietary lipids it consists mainly of triglycerides, in turn formed by the esterification of the three hydroxyl groups of glycerol with as many fatty acids.
A simple triglyceride is a triglyceride in which all three fatty acids are equal, while in mixed triglycerides one or more fatty acids differ from the rest.
The SAPONIFIABLE FRACTION of olive oil is made up of TRIGLYCERIDES (98 - 99%) simple (≈ 55%) and mixed (45%); it also contains minimal amounts of mono and diglycerides (glycerol esterified with one or two fatty acids).
Diglycerides can be 1, 2-diglycerides or 1, 3-diglycerides. The 1, 2 diglycerides are the triglyceride precursors and therefore derive from an incomplete biosynthesis, while the 1, 3 diglycerides derive from the triglyceride hydrolysis process.
This aspect is very important because the ratio of 1, 2 diglycerides to 1, 3 triglycerides gives us an idea of the state of conservation of the oil. If the 1, 2 prevail, which as we have said derive from the natural process of biosynthesis, it means that the oil is fresh, if the 1.3 prevails, which derive instead from enzymatic degradation, means that we are in the presence of an aged oil.
The composition in fatty acids varies according to the variety of the olive tree, the degree of ripeness of the drupes, the climate and the period of harvest. However, there are some particular fatty acids that represent almost all the fatty acids contained in olive oil; these are STEARICO, PALMITICO, OLEICO, LINOLEICO and LINOLENICO.
A characteristic that distinguishes olive oil from other vegetable oils is linked to its greater content in oleic acid; in seed oils, linoleic prevails instead.
In a good quality olive oil:
§ Oleic acid should not be less than 73%
§ linoleic acid should not exceed 10%
§ the oleic / linoleic ratio should be ≥ 7.
These characteristics allow olive oil to be kept longer than any other type of oil; the tendency to go rancid is in fact directly proportional to the number of double bonds present in fatty acids. While there is only one double bond in oleic acid (it is a monounsaturated), the linoleic acid contained in other vegetable oils contains two double bonds (it is a polyunsaturated parent of the omega-6 series). The rancidity of an oil is also hindered by the content of vitamin E and polyphenols; the latter abounding in olive oil and in grape seed oil.
A common characteristic of all vegetable oils, including olive oil, is that in the two position of the glycerol, therefore in the central one, an unsaturated fatty acid is ALWAYS located. This characteristic makes it possible to distinguish natural oils from those obtained by synthetic esterification.
Unsaponifiable fraction
It constitutes 1-2% of the lipid component of olive oil and contains:
- Hydrocarbons, including squalene (0.3-0.6 g%)
- Phytosterols, in particular b-sitosterol, campesterol, stigmasterol, both free and esterified
- liposoluble vitamins; b-carotene or provitamin A (3-37 g%) and tocopherols (Vit. E) have an antioxidant action that preserves the oil from rancidity and carries out a protective action on the health of the consumer
- pigments, chlorophyll and carotenes
- higher aliphatic alcohols esterified to fatty acids (waxes) and triterpene alcohols
- polyphenols, 2-3% mainly represented by glucosides and esters, also having an antioxidant action. The olive oil polyphenols are a complex mixture consisting of many substances among which oleoperine stands out.
