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.
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.
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 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 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. There are 3 main Omega-3 fatty acids:
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. 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% 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). Nutrients in Whole Olives, ripe, canned (jumbo-super colossal)
USDA National Nutrient Database for Standard Reference, Release 17 (2004)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 above. 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.
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. 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 %).
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hydrogenation process