Fatty Acids - trans fatty acid	Calories per tablespoon olive oil
Omega-3 fatty acids	Glycerolipids - Diacylglycerides (DAG)
Essential Fatty Acids	Chlorophyll
pH: ,  Polyphenols, Antioxidants	Color:
Peroxides,	Smoke Point
Vitamins:	Freezing Point of olive oil
Nutrients in Whole Olives,	Flavor Components of Olive Oil
Polycyclic aromatic hydrocarbons (PAHs):	Health Concerns - Cooking with Olive Oil
Storing Olive Oil  How olive oil goes rancid
	this page updated 04/14/2008

Books about Olive Oil Chemistry

Olive Oil Handbook of Olive Oil: Analysis and Production  Olive Oil - Chemistry and Technology

Olive Oil

Olive oil is a triacylgylceride: three fatty acids attached to a glycerol backbone.  Technically it is a type of glycerolipid.  Triacylglycerols (Triglycerides or Fats)  are the major energy reserve for plants and animals.

Fatty Acids: 

Olive Oil is a complex compound made of fatty acids, vitamins, volatile components, water soluble components and microscopic bits of olive.  Primary fatty acids are Oleic and linoleic acid with a small amount of linolenic acid.

• A fatty acid has the general formula:  CH3(CH2)nCOOH  where n is typically an even number between 12 and 22
• If no double bonds are present the molecule is called a saturated fatty acid.
• If a chain contains double bonds, it is called an unsaturated fatty acid.
• A single double bond makes a monounsaturated fatty acid
• Oils with more that one double bond are called polyunsaturated fatty acids.

• Oleic acid is monounsaturated and makes up 55-85% of olive oil
  (C17H35COOH)  or CH3-(CH2)7-CH=CH-(CH2)7-COOH also known as oleate.
  The IUPAC name would be cis-9-octadecenoate
• Linoleic is polyunsaturated and makes up about 9%
  (C17H29COOH) or  CH3-(CH2)4-CH=CH-CH2-CH=CH-(CH2)7-COOH
• Linolenic, which is polyunsaturated, makes up 0-1.5%

Hydrogenation:  Hydrogenated fat is created by bubbling hydrogen through 250 to 400 degree hot vegetable oil in the presence of a metal catalyst, usually nickel or platinum. The process can take several hours. Oleic acid (C18:1) and linoleic acid (C18:2) are both converted to stearic acid (C18:0) when fully saturated but fully saturated fats are too waxy and solid for use, hence the process is stopped at partial hydrogenation.  You cannot accidentally make trans or saturated fatty acids at home on your range when heating olive oil or other oils.

   hydrogenation process

Trans Fatty acids: Olive oil has no trans fatty acids.  When an oil is partially hydrogenated it can be in the cis or trans conformation which refers to which side of the fatty acid double bond the hydrogen is on. Olive oil is not a trans fatty acid because it has not been partially hydrogenated in a factory to make it solid at room temperature like margarine has. 

Long Chain Fatty Acids: Long chain fatty acids have from 12 - 20 carbon atoms.  The primary fatty acids in olive oil are all long chain fatty acids (oleic, linolenic and linoleic). Very long-chain fatty acids have greater than 20 carbon atoms.  These tend to be more solid at room temperature, such as waxes. There are not appreciable amounts of these in olive oil.

Glycerolipids and "Free" Fatty Acids

Fatty acids are rarely found free in cells.  The major class of lipids which contain fatty acids are the glycerolipids, the most common subclass of glycerolipids found in cooking oils are the triacylglycerols or triglycerides. A glycerolipid is a glycerol backbone with three acyl chains attached.  Fatty acids attach to the glycerol by the formation of ester bonds with the alcohol groups on the glycerol. In olive oil three alcohol groups on the glycerol are esterified to mainly Oleic acid as a triacylglycerol.  Only 2 of the groups are esterified  in diacylglycerol (DAG).  Olive oil has small amounts of DAGs.  DAGs have been found to lower body fat when fed to subjects as the primary fat source.

The levels of these acids (present as triacylglycerols) varies during the different maturation stages of the olive, varies with the variety and the growing conditions. It is generally accepted that cooler areas (eg Tuscany) will give an oil with higher oleic acid than warmer climates.

Percentage of Linolenic acid allowed in Olive Oil

Regarding the poly-unsaturated fatty acids (PUFAs) there is a wide range acceptable for EVO, however the Linolenic has to be less than 0.9% (IOOC). There is no problem if the levels are higher eg 1.5% regarding the olive oils nutritional value. But the IOOC uses the Linolenic acid level  to establish the authenticity of the olive oil. Seed oils like Canola have higher levels of Linolenic acid. Also the higher the level of unsaturation;,ie more PUFAs, leads to a less stable oil. This has to be counterbalanced by the levels of antioxidants that protect the oil.  These will also vary by similar factors to the fatty acid profile as well as stress eg drought. A higher Linolenic than the IOOC permits may actually be of benefit nutritionally for reasons other than those associated with oleic acid. - courtesy Stan Kailis

Essential Fatty Acids

In scientific writing the term essential fatty acid  refers to all the omega-3 or omega -6 fatty acids. This is a historical convention, not a medical definition.

From a medical point of view, Essential fatty acids are ones which the human body cannot make. There are only two, which are the building blocks from which many of the other omega-3 and omega-6 fatty acids are made in a healthy body. 

They are: Linoleic, an omega-6 fatty acid and alpha Linolenic, an omega-3 fatty acid.

 Omega-3 Fatty acids

There are 3 main Omega-3 fatty acids:

- ALA (Alpha-Linolenic Acid) - found in dark green leafy vegetables, seeds,  nuts, and a variety of vegetable oils like olive oil. 
- EPA (EicosoPentaenoic Acid) - found  in cold water fish like salmon, cod, mackerel, and tuna
- DHA (DocosaHexaenoic Acid) - fish - same as above

A healthy body can convert ALA to EPA and DHA so a diet rich in the seed oil alpha Linolenic acid does not need fish oil.

A large body of literature spanning numerous cohorts from many countries and with different demographic characteristics does not provide evidence to suggest a significant association between omega-3 fatty acids and cancer incidence. Omega-3 fatty acids are unlikely to prevent cancer.

Sources:

JAMA 2006;295:403-415 www.jama.com  

Omega-3 vs Omega-6

Olive Oil contains the two essential fatty acids. There is currently debate about how much omega-3 versus omega-6 one should have in their diet. The two fatty acids compete for space in the cell membranes. Studies show that there are benefits and risks to too much of either. While more of the omega-3 alpha Linolenic acid can help prevent heart disease, studies have suggested it may increase prostate cancer and macular degeneration7. According to the Merck Manual, an authoritative medical text, essential fatty acids should make up 1-2% of the dietary calories for adults with a suggested ratio of 10:1 for omega-6:omega-3 fatty acids.

Olive oil is about 10% linoleic acid (an omega-6 oil) and about 1% linolenic acid (an omega-3 oil), therefore the ratio is 10:1

If you were using only olive oil for your dietary fat and fats represented 30% of the calories in your diet, then you would be getting 3% of your calories in the form of essential fatty acids in a 10:1 ratio. Other more recent studies suggest closer to a 5:1 ratio may be more beneficial.

Sources:

Brouwer IA, Katan MB, Zock PL (2004). "Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis.". Journal of Nutrition 134 (4): 919-22.

Eunyoung Cho, Shirley Hung, Walter C Willett, Donna Spiegelman, Eric B Rimm, Johanna M Seddon, Graham A Colditz and Susan E Hankinson (2001). "Prospective study of dietary fat and the risk of age-related macular degeneration". American Journal of Clinical Nutrition 73 (2): 209-218.  

Other constituants: Phenols, free fatty acids, peroxide, triacylglycerols (TAG), diacylglycerols (DAG), and monoacylglycerols (MAG), thiobarbituric acid reactive substances (TBARS), Pheophytin A and  chlorophyll and many other substances make up olive oil.   

Antioxidants:  The flavenoid polyphenols in olive oil are natural anti-oxidants which have been shown to have a host of beneficial effects from healing sunburn to lowering cholesterol, blood pressure, and risk of coronary disease.  There are as many as 5 mg of antioxidant polyphenols in every 10 grams of olive oil. Many other nut and seed oils have no polyphenols.

Smoke Point  click for details

Calories per olive: It depends on how big the olives are and what their oil content is.  The large black canned olives are actually quite low in oil - sometimes only 7%, which is why they are table olives and are not used generally to make oil.  Some smaller olives used primarily for oil making can have up to 35% oil content.  Olives can range from 1 to 14 grams in weight. 

There is about 1 tablespoon of olive oil (and about 120 calories) in:

20 medium Mission olives that have an oil content of 20%
40 small ripe black olives
20 jumbo ripe black olives
7 super colossal ripe black olives

PAHs: Polycyclic aromatic hydrocarbons (PAHs):  Many foods naturally contain small quantities of PAHs.  Olive oil, like other vegetable cooking oils,  has been found to contain minute amounts of  up to 17 PAHs such as benzanthracene and chrysene.  Unripe olives tended to have more than ripe olives.  

Burning any cooking oil can increase the amounts of PAHs.  This is not considered a major risk source in the diet and the oil would have to be heated repeatedly and for extended periods to the smoking point.  It is unlikely that in home use olive oil or other cooking oils would be a significant source of PAHs.  

Freezing Point: Olive oil will harden at refrigerator temperatures - around 10 degrees F. Water is a pure substance so it freezes at an exact temperature. Olive oil is a complex mixture of oils and waxes. The heavier oils and waxes will form needle-like crystals as the temperature is lowered, then the other oils will start to settle out. Winterization is the commercial process whereby these waxes are removed to keep the oil clearer when stored on a cold shelf. It is used mostly for aesthetics and to improve mixing when combined into mayonnaise, sauces, and dressings.. Because olive oil is a natural product and different from year to year even from the same bottler, each batch of oil will "freeze" at a different temperature. There is no exact freezing temperature. Freezing olive oil will not harm it; it will actually prolong it's nutritional benefits and its flavor. It is a myth that the freezing point of olive oil can be used to predict whether it is pure, virgin or extra virgin.

pH:  refers to the hydrogen ion concentration in an aqueous solution. Olive oil and other oils are not water soluble so their acidity cannot be measured in terms of pH. Vegetable oils are very weak acids, when mixed with a strong base such as lye they will form a salt (commonly called soap). Better oils have a low acidity while lower quality oils will be more acidic.  Their acid content is usually measured in percent free acidity. Extra virgin olive oil must have less than .8% free fatty acid but some have less than .1%

Peroxides: Peroxides are the primary products of oxidation of olive oil. The more  rancid or oxidized the oil, the more peroxides are present.  

From: Tous, J. and L. Ferguson. 1996. Mediterranean fruits. p. 416-430. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Nutritional composition of Mediterranean crops (per 100 g of edible portion). Source: Goulart (1980); Sawaya et al. (1983); Fernandez Diez (1983); IBPGR (1986); Morton (1987); Cantwell (1994).