Well-documented by numerous studies around the world, the many health benefits of olive oil make it one of the most indispensable ingredients of a healthy diet. Naturally packed with monounsaturated fatty acids and antioxidants, not only can a good extra virgin olive oil lower your risk of heart disease and cancer, research has shown that it also provides a wide range of anti-inflammatory benefits that can positively impact illnesses such as diabetes, hypertension, arthritis, and asthma.
Even the FDA suggests that replacing just two tablespoons of aturated fat with extra virgin olive oil in your daily diet can have measurable positive effects.
Where in the world did the olive originate?The olive was native to Asia Minor and spread from Iran, Syria and Palestine to the rest of the Mediterranean basin 6,000 years ago. It is among the oldest known cultivated trees in the world – being grown before the written language was invented.
It was being grown on Crete by 3,000 BC and may have been the source of the wealth of the Minoan kingdom. The Phoenicians spread the olive to the Mediterranean shores of Africa and Southern Europe. Olives have been found in Egyptian tombs from 2,000 years BC.
The olive culture was spread to the early Greeks then Romans. As the Romans extended their domain they brought the olive with them.
Olea is a genus about 20 species in the family Oleaceae, native to warm temperate and tropicalregions of southern Europe, Africa, southern Asia and Australasia. ? There is only one species inthis genus, europaea which produces the edible olives and oil commonly consumed. It is by far the most important species, native to the Mediterranean region. O. paniculata is a larger tree, attaining a height of 15-18 m in the forests of Queensland, and yielding a hard and tough timber. The yet harder wood of the Black Ironwood O. laurifolia, an inhabitant of Natal, is important in South Africa.
Because sensory analysis is subjective by nature (consider how some people deplore spicy foods while others can’t get enough…), certified panel scores reflect a compilation of the panel’s results rather than an individual’s score. Detailed methods describe the condition of the tasting environment, sample preparation and tasting tools and even a list of rules tasters must follow such as no coffee, eating or smoking before sessions. Every effort is made to minimize bias and train the tasters to be objective in their work. Detailed information on IOC
organoleptic assessment can be found on its website here.
Sensory panels use a line scale to rate olive oil’s intensity on three positive attributes:
Preference can emerge especially where bitterness and pungency are concerned but these are considered positive attributes. From a quality and marketability perspective, the balance of these positive attributes is a key consideration.
The intensity of negative attributes is also rated by the panel and the IOC specifies five most common defects:
To be deemed extra virgin, the oil must not have any defects and must have a median fruity score greater than zero. Given that the range of flavors is so broad, it is important to remember a “different”; taste is not necessarily “bad”. Sensory perception is highly influenced by personal history and familiarity and professional tasters need to become adept at naming specific sensations so they avoid mistaking a new taste for a defect.
Panelists need to practice and be exposed to oils from a broad range of regions, olive varieties and times of harvest. This is one reason the IOC requires certified sensory panels to successfully complete ring-tests using pre-identified oils each year in order to maintain the panel´s certification.
Olive oil is composed mainly of triacylglycerols (triglycerides or fats) and contains small quantities of free fatty acids (FFA), glycerol, phosphatides, pigments, flavor compounds, sterols, and microscopic bits of olive. Triacylglycerols are the major energy reserve for plants and animals.
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 carbon atoms in length.
The major fatty acids in olive oil triacylglycerols are:
• Oleic Acid (C18:1), a monounsaturated omega-9 fatty acid. It makes up 55 to 83% of olive oil.
• Linoleic Acid (C18:2), a polyunsaturated omega-6 fatty acid that makes up about 3.5 to 21% of olive oil.
• Palmitic Acid (C16:0), a saturated fatty acid that makes up 7.5 to 20% of olive oil.
• Stearic Acid (C18:0), a saturated fatty acid that makes up 0.5 to 5% of olive oil.
• Linolenic Acid (C18:3)(specifically alpha-Linolenic Acid), a polyunsaturated omega-3 fatty acid that makes up 0 to 1.5% of olive oil.
Triacylglycerols are normally composed of a mixture of three 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), and so on.
Olive oil contains more oleic acid and less linoleic and linolenic acids than other vegetable oils, that is, more monounsaturated than polyunsaturated fatty acids. This renders olive oil more resistant to oxidation because generally, the greater the number of double bonds in the fatty acid, the more unstable and easily broken down by heat, light, and other factors the oil is. It is generally accepted that cooler regions (e.g. Tuscany) will yield oil with higher oleic acid than warmer climates. That is, a cool region olive oil may be more monounsaturated in content than a warm region oil.
Trans Fatty Acids
Note that olive oil has no trans fatty acids. When oil is partially hydrogenated, it can be in the “cis” or “trans” conformation; this 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 to 20 carbon atoms. The primary fatty acids in olive oil are all long chain fatty acids. 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.
Percentage of Linolenic Acid Allowed in Olive Oil
Regarding the polyunsaturated fatty acids (PUFAs), there is a wide range acceptable for extra virgin olive oil, however the linolenic acid has to be less than 0.9% per the International Olive Oil Council (IOOC) guidelines. Higher levels, e.g. 1.5%, do not present a nutritional problem, but the IOOC uses the linolenic acid level to establish the authenticity of the olive oil. Seed oils like canola oil have higher levels of linolenic acid.
“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 the ones that 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: linoleic acid and alpha-linolenic acid.
Olive oil will harden at refrigerator temperatures – around 37-39°F. Determining at what point to call the oil “frozen” is a matter of semantics. The slow increase in hardening as the temperature is lowered is in sharp contrast to a pure substance such as water that switches from a liquid to solid phase 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.
At 40°F most of the oils would not harden or form any crystals. At 35°F most are firm enough that they cannot be poured but are as soft as butter at room temperature. As the temperature is lowered, more components of the oil solidify. At 10°F the oil is hard enough that a fork cannot penetrate it.
Winterization is the commercial process whereby these waxes are removed to keep some oils clearer when stored on a cold shelf. It is used mostly for aesthetics and to improve mixing when combined into mayonnaise, sauces, and dressings.
Olive oil is a natural product that varies from year to year even from the same producer, so each batch of oil will “freeze” at a different temperature. Freezing olive oil will not harm it; it will actually prolong its 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. To learn more about this subject, read our Freezing Olive Oil page.
Peroxides are the primary products of oxidation of olive oil. Fats and oils such as olive oil are oxidized when they come in contact with oxygen. Oxygen may exist in the headspace of the container and dissolve in the oil. The oxidation products have an unpleasant flavor and odor and may adversely affect the nutritional value of the oil. Essential fatty acids such as linoleic and linolenic are destroyed, and certain fat soluble vitamins disappear. Fatty acids are oxidized by one of the following mechanisms.
Auto-oxidation occurs in the absence of air by reactive oxygen species or “free radicals”. It is temporarily prevented by the natural antioxidants in the oil that absorb these free radicals. When the antioxidants are used up, the oil ages quickly.
Photo-oxidation occurs when the oil is exposed to natural and/or artificial light sources (including halogen lights and store lights). It causes serious deterioration of olive oil, as it can occur up to 30,000 times faster than auto-oxidation.
The more rancid or oxidized the oil, the more peroxides are present. Measurement of the peroxides in olive oil is a very simple procedure which can done at a testing lab. High quality extra virgin olive oils have a peroxide value of less than 10meq/kg. In order to be extra virgin, olive oil must have less than 20 meq/kg.
The unique color of olive oil is due to pigments like chlorophyll, pheophytin, and carotenoids. The presence of various pigments depends on factors such as the fruit ripeness, the olive cultivar, the soil and climatic conditions, and the extraction and processing procedures.
According to Apostolos Kiritsakis, one of the premier researchers on olive oil components, fresh olive oil contains between 1 and 10 parts per million chlorophyll. This is miniscule compared to a portion of spinach. Olives are invariably crushed with some leaves still present, so some of the chlorophyll comes from that source. Some producers have been known to deliberately allow leaves in the mill to increase the “grassiness” of the oil.
In the light, chlorophyll and pheophytin 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.
What factors determine the color of olive oil?The color of olive oil can vary from a light gold to a rich green. Green olives produce a green oil because of the high chlorophyll content. Ripe olives yield a yellow oil because of the carotenoid (yellow red) pigments. The exact combination and proportions of pigments determine the final color of the oil.
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.
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.
The flavenoid polyphenols in olive oil are natural antioxidants that contribute to a bitter taste, astringency, and resistance to oxidation. They have been shown to have a host of beneficial effects from healing sunburn to lowering cholesterol, blood pressure, and risk of coronary disease. Read more about the health benefits of these critical components of olive oil.
Hydroxytyrosol and tyrosol are some of the many phenol compounds in olive oil. There are as many as 5 mg of polyphenols in every 10 grams of olive oil. Many other nut and seed oils have no polyphenols. The polyphenol content is determined by many factors including:
• Olive Varietal: Koroneiki olives, for instance have a very high level of polyphenols, while Arbequina’s content is low. The content of Frantoio olives is medium-high and that of Leccino medium.
• Time of Picking: Oil made from green (unripe) olives has more polyphenols than oil made from ripe olives. The polyphenol concentration increases with fruit growth until the olives begin to turn purple and then begins to decrease.
• Environmental Factors such as altitude, cultivation practices, and the amount of irrigation.
• Extraction Conditions: Techniques used to enhance yield, such as heating the paste, adding water, and increasing malaxation time, result in a loss of polyphenols.
• Storage Conditions: The type of containers and the length of storing are key factors in the oil’s polyphenol content. As oil sits in storage tanks or in a bottle, the polyphenols will slowly be oxidized and used up. Oils stored in stainless steel containers or dark glass bottles, in cool conditions, are much better protected against oxidation than those bottled in clear glass.
An interesting related fact: Gary Beauchamp and other chemists published a September 1, 2005 article in Nature that shows that oleocanthal, the pungent compound in some oils which creates a stinging sensation in the throat, has similar properties to anti-inflammatory compounds such as
Refining: Olive oil which is old, rancid, made from diseased olives, or has some other defect can be made palatable by refining. This is done by filtering, heating, charcoal, or chemical treatment to adjust acidity. Refined oils are low in tyrosol and other phenols.
Vitamins can be divided into the fat soluble and water soluble varieties. Fat soluble vitamins, such as the ones found in olive oil, are generally 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. Cured whole olives have both water and fat soluble vitamins.
Vitamin E (a natural antioxidant): Olives have 1.6mg, or 2.3 IU (International Units) per tablespoon. One tablespoon provides 8% of RDA for vitamin E.
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. According to the USDA , vegetable oils such as olive oil are the second best source.
The combined pool of compounds in olive oil that are in the phenolic chemical group (containing six carbon atoms attached to each other in a ring like formation with one or more oxygen+hydrogen groups attached to the ring).
An example of a common olive oil polyphenol is shown in Figure 1. ‘total polyphenols’ are a measure of thecombined total of the most important group of antioxidants in extra virgin olive oil.
Figure 1: Hydroxytyrosol – An example of a phenolic compound found in extra virgin olive oil.
The polyphenols are extracted from the oil into a water/alcohol mix. A reagent is added which reacts with the polyphenols turning it blue/green. The depth of the blue/green colour is measured, and is directly proportional to the amount of polyphenols in the sample.
Higher polyphenols which are of the antioxidant family could be perceived to be of higher quality.
The Polyphenols analysis, were Initially developed for wine polyphenols. It was officially adopted in a modified for olive oil by the International Olive Council in 2005.
The unit of measurements are in milligrams/kilogram of oil (1mg=1/1,000 of a gram).
Range in Extra Virgin Olive Oil: 80-2,000 mg/kg (measured as caffeic acid equivalents). Common range 200-400 mg/kg.
Analytical method: first step of the analysis involves extracting the polyphenols out of the oil using a solvent.
And it will depend on how carefully it is done, can cause variable end results in the order of +/- 10%. For this reason, it is necessary to repeat the test and take an average.
Cultivar – some varieties of olives tend to produce naturally higher polyphenol levels than others. For example, the average polyphenol levels in oils made from the cultivar ‘Picual’ are significantly higher than those made from the cultivar ‘Arbequina’.
Olive maturity at harvest – The greener the olives used to make the oil, the higher the polyphenol levels.
Climate – Cool climates tend to favour higher polyphenol levels.
Tree water status – Excessive water availability reduces polyphenol levels.
Enzymes – The use of enzymes as a processing aid increases polyphenol levels
Water use during processing – Adding water to olive paste before extraction (e.g. 3 phase processing) reduces polyphenol levels.
Post harvest – Delays between harvest and processing reduce polyphenol levels.
Disease/Fruit quality – Incidence of fungal disease, olive fly attack and frost damage decreases polyphenol levels.
Age of the oil – Polyphenols levels decline as the oil ages.
The method only measures the size of the entire pool of the hundreds of polyphenol types that exist in extra virgin olive oil. Information about the amount of a specific polyphenol can only be achieved using highly sophisticated methods called high performance liquid
chromatography or HPLC.
Free Fatty Acidity or FFA- ‘Free Acidity’ or simply ‘Acidity’
What does it measure?, the level of breakdown of the fats in extra virgin olive oil.
The analytical technique is easy to do it. Can be done using basic lab equipment and little technical expertise.
Range limits for extra virgin status: > 0.1 % < 0.8%
Unofficial limit strived for by good EVOO producers: <0.2%
Direct effects of high quantities of FFA:
Typical indirect effects of high FFA:
How to reach high FFA:
Every fat molecules including that in olive oil is comprises 3 smaller parts called fatty acids that are connected together. Figure 1 is the typical fat molecule found in olive oil – three monounsaturated fatty acids called oleic acid linked together.(By Richard Gawel)
Figure 1: Extra Virgin Olive Oil Nirvana. A perfectly formed and intact fat typical of olive oil.
However, having 100% perfectly intact fats like those shown in Figure 1 molecules is “fat Nirvana”. Sort of like that place that the “Watchtower” magazines portray – where humans live in perfect harmony with dopey lions and really small monkeys (both of which are likely to kill you at any given moment, but somehow reassuringly, for different reasons). But, getting back to the point, extra virgin olive oil is a natural product, and therefore is less than perfect. Individual fatty acids can be chopped off the fat molecule if the olives are riddled with fungussy olive pestilence, are being gouged upon by olive fly maggots, bruised and battered during harvesting, or (more typically, and less dramatically) if the olives are left to even slightly decay in the interim between olive harvest and processing.
Figure 2: Formation of free fatty acids. The Pacman represents a lipase enzyme, but if you like, you can think of it as a Pacman.
Nature has devised a few ways of busting up intact fat molecules to form free (aka single) fatty acids. Her chopping utensil of choice are enzymes called lipases.
They are found in the olive fruit, but in good fresh undamaged olives the lipases are harmlessly locked up in the olive cell away from the fat molecules that they desperately want to destroy. But when the olive cells are damaged in any way, the enzymes are able to escape from their compartments, and in frenzied attacks dismember the intact fat molecules freeing up fatty acid molecules (Figure 2). The more diseased the olive, or the longer the time gap between olive harvesting and processing, the more enzymatic activity and the higher the free fatty acidity.
“FFA is a good indicator of olive oil quality” – Sort of right.
Free fatty acidity is widely acknowledged as a good index of general olive oil quality. While this is generally true, I have tasted many examples of higher FFA extra virgin olive oils that taste just fine, and conversely I have tasted many low FFA oils that are woefully defective. Take for example what is possibly the worst tasting defect in olive oil called muddy sediment. It has a foul (for olive oil) taste of parmesan cheese, baby vomit, salami, band-aids, horse stable and fetid milk (and combinations of these). An olive oil can pick up these characters from short term exposure to the particulate olive sediment that remains after oil extraction and which later falls to the bottom of a tank.
The aroma compounds that contribute to this defect are very potent. Therefore whilst leaving the oil on the sediment may result in only a small break down of the fat (resulting in a small increase in FFA), this small increase in FFA can be accompanied by a large reduction in flavour quality.
“Refined olive oils have high FFA” – Very wrong!
Paradoxically nothing is further from the truth. Refined olive oils (i.e. those labelled as pure, light and ‘olive oil’ ) have essentially zero FFA. Yep, zero. The confusion probably arises from the fact that badly made olive oils, i.e. oils with very high FFA’s are those destined for refining in the first place. The major purpose of the refining process is to remove the free fatty acids. This is effectively acheived by adding caustic soda which converts the free fatty acids to soap which can then be physically removed from the oil.
“The FFA of an EVOO increases substantially during storage” – It is not correct again.
The production of free fatty acids from intact fat molecules is process that mostly involves the action of enzymes found within the olive which act in the presence of water. Once an olive oil has been properly extracted from the olive and most of the water has been removed (<0.1% remaining), further degradation in bottle leading to higher FFA is very unlikely. Typically, a properly processed EVOO with a low FFA of 0.2% at the time of processing, may get up to between 0.22% and 0.25% after 12 months of storage. Ok, that’s a 10-20% increase, but when you consider that your typical inexpensive supermarket purchased EVOO from the EU typically starts at 0.60-0.80% the 0.02-0.05 increase in FFA due to storage is inconsequential.
“You can’t taste acidity in olive oil” – Got that one right.
The free fatty acids are so weak that they don’t have the ability to bother our otherwise very busy acid taste receptors.
“If the FFA of an olive oil is X% measured as oleic acid , this mean that the olive oil contains X% oleic acid”. – NO it does not mean that.
The “measured as oleic acid” is simply a unit of measurement. For a few anally retentive lipid chemists, it may seem important, but in reality, whichever fatty acid equivalent (pick one, any one), it really has bugger all effect on the final result. So everyone can ignore the “measured as” bit without any loss of meaning.