see also Coconut Oil
ARTICLE #3 FDA: Olive oil may fight heart disease
Olive oil is a triagylceride: 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.
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 monosaturated 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%
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. Trans 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. You cannot accidentally make trans fatty acids at home on your range when heating olive oil or other oils.
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.
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 Linolenic acid level is used 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 may actually be of benefit nutritionally for reasons other than those associated with oleic acid. - courtesy Stan Kailis
Omega-3 and Omega-6 fatty acids: Olive Oil contains both omega-3 and omega-6 fatty acids. Omega-3 fatty acids are important in preventing cardiovascular disease and are particularly high in oily fish such as salmon. While olive oil is not terribly high in omega-3, the ratio of the two omega acids has been found to be more important and olive oil has a great ratio.
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: Smoke Point is related to free fatty acid content. Below is a table which shows this relationship for a typical cooking oil. Most people who are planning to deep fry with olive oil use a refined oil such as a pure or an "extra light" olive oil. See cooking considerations. The International Olive Oil Council states that olive oil has a smoke point of 210 degrees C (410 degrees F).
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 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.
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 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.
Vitamins Vitamins can be divided into the fat soluble and water soluble varieties. Because olive oil is a fat, it is higher in the fat soluble vitamins A, D, E and K. Fat soluble vitamins generally are not broken down by cooking. They are stored in the liver and body fat for long periods so it is not essential to eat them with every meal. Because they are stored, eating too much can lead to toxicity. Cured whole olives have both water and fat soluble vitamins.
Vitamin E (a natural antioxidant) per tablespoon - 1.6mg, or 2.3 IU (International Units)
One tablespoon provides 8% of RDA for vitamin E.
Studies show that people who eat antioxidant rich foods such as vegetable oils, fruits, vegetables, grains and nuts have a lower chance of getting heart disease and cancer. It was assumed that taking Vitamin E supplements would do the same but oddly enough newer studies show that this is not true. 10,000 patients at high risk for heart attack or stroke were followed for 4.5 years in the The Heart Outcomes Prevention Evaluation (HOPE) Study. People who received 265 mg (400) IU of vitamin E daily did not experience significantly fewer cardiovascular events or hospitalizations for heart failure or chest pain when compared to those who received placebo. It seems that you must eat the whole foods to get the benefit.
Vitamin K: The richest sources of vitamin K are green, leafy vegetables. One serving of spinach or collards, for instance, or two servings of broccoli provide four to five times the RDA. The greener the vegetable, the higher the content, say the researchers, because the vitamin is associated with the chlorophyll. Vegetable oils--soybean, canola and olive--and dressings containing them are the second best source - USDA
Color: "The color of olive oil is dependant on the pigments in the fruit - Green Olives give a green oil because of the high chlorophyll content. Ripe olives give a yellow oil because of the carotenoid (yellow red) pigments. The color of the oil is influenced by the exact combination and proportions of pigments. A simple equation would be Color = Chlorophyll (Green) + Carotenoids (Yellow red) + other pigments. Color is not an official standard but it certainly excites the consumer." Professor Stan Kailis, University of Western Australia, Perth, WA
Chlorophyll: Chlorophyll is one of the main pigments in olive oil. The chlorophyll content decreases as the fruit matures so olives picked green produce a greener oil with a "grassy" flavor. According to Apostolos Kirisakis, one of the premier researchers on olive oil components, fresh olive oil contains between 1 to 10 parts per million. Miniscule compared to a portion of spinach. The olive cultivar, weather, pressing method, etc. also determine chlorophyll content. Olives are invariably pressed with some leaves still present so some of the chlorophyll comes from that source. Some producers have been know to deliberately allow leaves in the mill to increase the "grassiness" of the oil. In the light, chlorophyll will promote formation of oxygen radicals and speed up oxidation but in the dark chlorophyll acts as an antioxidant. In current physiological studies, chlorophyll is broken down in the body and has no effect as an oxidant or antioxidant.
Flavor Components of Olive Oil--A Review, A.K. Kiritsakis*, Department of Food Technology, School of Food Technology and Nutrition, Technological Educational Institution (TEI) of Thessaloniki, Sindos Thessaloniki, Greece.
Following is the abstract of a Journal of the American Oil Chemist Society which describes many of the volatile substances. Contact American Oil Chemists' Society (AOCS) for full article (or the author).
The unique and delicate flavor of olive oil is attributed to a number of volatile components. Aldehydes, alcohols, esters, hydrocarbons, ketones, furans, and other compounds have been quantitated and identified by gas chromatographymass spectrometry in good-quality olive oil. The presence of flavor compounds in olive oil is closely related to its sensory quality. Hexanal, trans-2-hexenal, 1-hexanol, and 3-methylbutan-1-ol are the major volatile compounds of olive oil. Volatile flavor compounds are formed in the olive fruit through an enzymatic process. Olive cultivar, origin, maturity stage of fruit, storage conditions of fruit, and olive fruit processing influence the flavor components of olive oil and therefore its taste and aroma. The components octanal, nonanal, and 2-hexenal, as well as the volatile alcohols propanol, amyl alcohols, 2-hexenol, 2-hexanol, and heptanol, characterize the olive cultivar. There are some slight changes in the flavor components in olive oil obtained from the same oil cultivar grown in different areas. The highest concentration of volatile components appears at the optimal maturity stage of fruit. During storage of olive fruit, volatile flavor components, such as aldehydes and esters, decrease. Phenolic compounds also have a significant effect on olive oil flavor. There is a good correlation between aroma and flavor of olive oil and its polyphenol content. Hydroxytyrosol, tyrosol, caffeic acid, coumaric acid, and p-hydroxybenzoic acid influence mostly the sensory characteristics of olive oil. Hydroxytyrosol is present in good-quality olive oil, while tyrosol and some phenolic acids are found in olive oil of poor quality. Various off-flavor compounds are formed by oxidation, which may be initiated in the olive fruit. Pentanal, hexanal, octanal, and nonanal are the major compounds formed in oxidized olive oil, but 2-pentenal and 2-heptenal are mainly responsible for the off-flavor.
JAOCS 75, 673681 (1998).
A discussion of the chemical properties of olive oil: Aberystwyth, Wales
A Great discussion of olive oil chemistry by Guido Costa in simple terms
Herewith my contribution on FATTY ACIDS AND ACIDITY: Olive oil is composed mainly of triacylglycerols (triglycerides). Chemically speaking, these are molecules derived from the natural esterification of three fatty acid molecules with a glycerol molecule. The glycerol molecule can simplistically be seen as an "E-shaped" molecule, with the fatty acids in turn resembling longish hydrocarbon chains, varying (in the case of olive oil) from about 14 to 24 carbons atoms in length. Thus the triacylglycerols can, for our purpose, be visualized as elongated E-shaped molecules, each with three long extensions, being the three fatty acid chains "attached to each horizontal bar of the E".
Please note that we are dealing here with fatty acids forming part of the triacylglycerols molecule. They are distinct from FREE FATTY ACIDS, which we'll talk about later!
Various fatty acids are found in nature. They differ in length (number of carbon atoms in the chain) as well as in the type of chemical bonds found within the chain. Mostly these carbon-carbon bonds in the chain are "single" bonds, comprising 2 electrons shared between adjacent carbon atoms. However, in certain of the fatty acids, some of the bonds are "double bonds", where 4 electrons are shared between adjacent carbon atoms. The fatty acids that have no double bonds in their chains are called "saturated" fatty acids (all the carbons in their carbon chain are "saturated" by hydrogen atoms). Examples of saturated fatty acids are Palmitic Acid (16 carbons long), Stearic Acid (18 carbons long) and Arachidic Acid (20 carbons long). The fatty acids that have one carbon-carbon double bond somewhere along their length are called monounsaturated fatty acids (one carbon-carbon bond which is not fully saturated with hydrogens), i.e. one of the bonds available at each of 2 adjacent carbons is now used to form a double bond between themselves instead of being used to bond externally to hydrogen atoms. Examples of monounsaturated fatty acids are Palmitoleic Acid (16 carbons long) and our famous Oleic Acid (18 carbons long). Oleic acid is the most abundant fatty acid found in nature. The double bond in Oleic acid occurs in the mid position of the molecule, between carbon 9 and carbon 10.
I don't want to make this sound too complicated, but as soon as one brings a double bond into the picture, one must bear in mind that, unlike the single bonds (wherein the molecular chain has complete rotational freedom of movement in the bond axis), the double bond is a rigid bond insofar as it does not allow rotation around its longitudinal axis. Thus, with each double bond, one introduces what are called isomers. These have the same chemical structure, but different stereochemistry. In other words, the shape of the molecule differs, and so does its chemical reactivity (and effect on health). This leads to things like "trans" fatty acids (TFA's) and "cis" fatty acids (CFA's). Trans fatty acids are normally produced when oils are artificially and chemically converted into margarines. They are said to raise LDL's (the "bad" cholesterol) and lower HDL's (the "good" cholesterol), and are thus to be avoided. Oleic acid is a cis fatty acid, and more specifically a cis monounsaturated C18 acid. Cis means the rest of the chain is "on the same side" of the bond axis as the carbon chain prior to the double bond, and trans means "on opposite sides" of the bond axis. Wow, is there anyone still reading this!?
Well, we're not yet finished. Now for polyunsaturated fatty acids. If you've understood the above, they're a simple extension - just more than one double (unsaturated) bond along the length of the fatty acid carbon chain. In olive oils the maximum number of double bonds per fatty acid is three, whereas one can get up to six unsaturated double bonds in certain fatty acids derived from fish. Generally, however, the greater the number of double bonds in the fatty acid, the more unstable, and more easily broken down by heat, light, etc. That's why olive oil, made up predominantly of monounsaturated oleic acid, is so much more heat-stable than the highly polyunsaturated seed oils. Olive oil can, for example, be re-used substantially more often in frying than other seed oils (including canola, which has about three times the amount of polyunsaturation than olive oil). An example of a polyunsaturated fatty acid with two unsaturated double bonds along its carbon chain is Linoleic Acid (18 carbons long). Linolenic Acid has three double bonds in its carbon chain, and is also 18 carbons long.
Triacylglycerols are normally composed of a mixture of three of the some of the above-mentioned fatty acids. Most prevalent in olive oil is the oleic-oleic-oleic (OOO) triacylglycerol, followed, in order of incidence, by palmitic-oleic-oleic (POO), then oleic-oleic-linoleic (OOL), then palmitic-oleic-linoleic (POL), then stearic-oleic-oleic (SOO), etc.
Now lets look ACIDITY, which is probably the most fundamental quality measurement of an edible oil.
As we know, freshly pressed oil, made from sound, healthy, freshly picked olives, normally has a pretty low "acidity", in the order of well under 0,5%. This "acidity" is the result of a degree of breakdown of the triacylglycerols due to a chemical reaction called hydrolysis, in which free fatty acids are formed. (In exceptional circumstances, even oils made from fresh, healthy olives can have significant amount of acidity, caused by anomalies during the actual biosynthesis of the oil in the olive fruit). Once the oil has been extracted, however, carelessness can lead to a very significant further breakdown of the triacylglycerides into fatty acids - these "broken off" fatty acids being called FREE FATTY ACIDS. Sometimes just one of the three fatty acids breaks off, leaving a diacylglycerol. If two fatty acids break off a certain triacylglycerol, we're left with a monoacylglycerol. If all three break off, we're left with glycerol.
Factors which lead to a high free fatty acidity in an oil are: fruit fly infestation of fruit, delays between harvesting and extraction, especially if the fruit has been bruised or damaged during harvesting, fungal diseases in the fruit (gloesporium, macrophoma, etc.), prolonged contact between oil and vegetation water (after extraction), etc. Thus we see that the traditional way in which olives are/were stored in heaps/silos to encourage enzymatic breakdown of cell structure so as to facilitate oil release (as practiced in Portugal, etc.) is certainly not conducive to producing a high quality, low acid oil.
The free fatty acidity is thus a direct measure of the quality of the oil, and reflects the care taken right from blossoming and fruit set to the eventual sale and consumption of the oil.
Measurement of FFA (free fatty acidity) is a very simple procedure. The principle is based on dissolving the free fatty acids present in a carefully weighed sample of oil into a mixture of solvents (usually alcohol/peroxide-free ether), and then titrating, with constant stirring, against a standard alkali solution (usually standardized Potassium Hydroxide) in the presence of an acid/base indicator (usually phenolpthalein). The results are presented as grams oleic acid per 100 grams oil, commonly known as the free fatty acidity (ffa or acidity) of the oil (in %).
Storage and rancidity. Olive Oil can be stored in containers as mundane as plastic or as indestructible as stainless steel. Researchers have shown that oil stored in polyethylene bottles exposed to light can develop unacceptable limits of peroxide in as little as 20 days while if stored in dark it can last 120-190 days
Rancidity is most commonly detected by taste but a chemical test can also check for rancidity. The chemical method is mostly used for large industrial frying operations. Oil doesn't suddenly go rancid, it slowly becomes more oxidised and as it does, the flavor suffers. A two year old olive oil may taste rancid to some while others don't mind it. Most people would be put off by the taste of any vegetable oil more than 4-5 years old. Rancid oil has fewer antioxidants but is not poisenous. A good percentage of the world's population routinely eat rancid oil because of lack of proper storage conditions and some actually prefer the taste. In historical times olives which had dropped to the ground or which may have spoiled were made into olive oil which was stored in open-mouthed earthenware vats. Practices like these encouraged rancidity. People have come to expect non-rancid oil in the past 50 years because of chemical refining and better production methods.
Oil deteriorates through the action of lipase and other enzymes in the oil and the action of oxygen. Oxidation or rancidity speeds up when the oil is exposed to light and heat. Keeping your oil next to the stove in a clear bottle will quickly age it. Better to keep a large container in a dark, cool cupboard and pour a small amount into a dispenser for everyday use. Olive oil can be put into the refrigerator or freezer without harm, which will greatly extend its shelf life. Waxes in the oil may crystallize out into needles or a slurry when the oil is chilled. Warming the oil back to room temperature will re-liquefy it.
"Auto-oxidation" occurs in the absence of air and is prevented by natural anti-oxidants in the oil. Oil from green olives have higher levels of anti-oxidants and some varieties naturally have higher levels than others. Blending an oil high in antioxidants with a more bland oil can greatly extend its shelf life. Auto-oxidation proceeds slowly until all anti-oxidants are used up at which time the oil quickly becomes rancid. This can happen in 1 to 3 years depending on oil storage conditions and variety. Sometimes an old oil will taste fine when first exposed to the air but a few weeks later can taste old and oxidized whereas a new oil will last for months after opening. Look for olive oil brands which date their oil. Note that for oil made in the northern hemisphere and sold in the year 2003 will often have been picked in the fall and winter of 2002. It is the freshest oil you can buy even though it may be dated the year before.
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Study shows why Mediterranean diet is good for you
Scientists have discovered why eating a Mediterranean diet rich in fruits, vegetables and particularly olive oil can help to protect women from developing breast cancer.
The key is oleic acid, the main component of olive oil.
Dr Javier Menendez, of Northwestern University Feinberg School of Medicine in Chicago, said oleic acid blocks the action of a cancer-causing oncogene called HER-2/neu which is found in about 30 percent of breast cancer patients.
“We have something now that is able to explain why the Mediterranean diet is so healthy,” Menendez told Reuters.
Doctors and researchers had been aware that eating a Mediterranean diet reduced the risk of breast cancer and other illnesses such as heart disease. But until now they did not know how.
Menendez and his colleagues in the United States and Spain studied the impact of oleic acid in laboratory studies of breast cancer cells.
“We are able to demonstrate that the main component of olive oil, oleic acid, is able to down-regulate the most important oncogene in breast cancer,” Menendez explained.
“The most important source of oleic acid is olive oil.”
The monounsaturated fat in olive oil may reduce the chances of suffering coronary heart disease, the Food and Drug Administration said Monday, opening the door to revised food labels.
As long as people don’t increase the number of calories they consume daily, the FDA found “limited but not conclusive evidence” suggesting reduced risk of coronary heart disease when people replace foods high in saturated fat with the monounsaturated fat in olive oil.
According to the American Heart Association, coronary heart disease accounted for 502,189 deaths or one in five deaths in 2001, the most current statistic available. Another 13.2 million Americans that year survived the heart attacks, chest pains and other ailments caused by coronary heart disease.
Along with lowering cholesterol, cutting out cigarettes and exercising, the group says Americans can boost heart health by eating foods low in saturated fat, cholesterol and sodium. An American Heart Association spokeswoman declined comment on the FDA’s action until it reviews the health claim.
“Since CHD is the No. 1 killer of both men and women in the United States, it is a public health priority to make sure that consumers have accurate and useful information on reducing their risk,” Lester M. Crawford, acting FDA commissioner said in a prepared statement.
It’s the third time the FDA granted a qualified health claim for conventional food.
Olive oil and certain food containing olive oil can now indicate that “limited and not conclusive scientific evidence suggests that eating about two tablespoons (23 grams) of olive oil daily may reduce the risk of coronary heart disease due to the monounsaturated fat in olive oil,” the agency said.