Vegetable oils are oils derived from plant sources. Examples are palm oil, corn oil, soybean oil, cottonseed oil, coconut oil and palm kernel oil.
Although “tropical oils” are often assumed to be palm oil, palm kernel oil and coconut oil, there is no legal or technical definition of the term “tropical oils”.
Palm oil is used in such products as bread and rolls, pancakes, waffles, crackers, ready to eat cereals, chips, popcorn, biscuits, tarts, cakes, pies, canned puddings, chocolates, coffee whitener, nondairy toppings, infant formulas, cocoa mixes, fried potatoes and onions, soups, gravies and frozen and dry mix entrees. Palm oil is also especially useful in the manufacture of margarines, since it imparts natural colouring and a high glyceride content without hydrogenation. As a frying fat, palm oil has a high resistance to oxidation and does not leave an unpleasant room odour, due to the absence of linolenic acid in its composition.
Palm oil is found in the fleshy portion of the fruit (mesocarp), whereas palm kernel oil is found in the kernel or seed of the fruit. The two oils have very different fatty acid compositions. Palm oil is 50% saturated fat and 50% unsaturated fat. More specifically, palm oil contains approximately 44% palmitic acid, 5% stearic acid, 39% oleic acid (monounsaturates), and 10% linoleic acid (polyunsaturates). Myristic acid and lauric acid are negligible.
Conversely, the fatty acid composition of palm kernel oil resembles coconut oil, or what one generally thinks of when the term ‘saturated fat’ is used. Approximately 82% of palm kernel oil is saturated fat with the main contributors being 48% lauric acid, 16% myristic acid, and 8% palmitic acid. Approximately 18% of palm kernel oil is unsaturated fat with 15% oleic acid (monounsaturates) and 3% linoleic acid (polyunsaturates).
The specific fatty acids were provided as current research suggests that all saturated fat cannot be simply classified as “bad” in relation to blood cholesterol levels. Each fatty acid demonstrates its unique characteristic on cholesterol regulation. Please see “Are all saturated fats bad?” for more information.
Palm oil, unlike other oils, is composed of 44% palmitic acid. Palmitic acid is a C16 saturated fatty acid, and is now found to be less hypercholesterolemic than saturated fatty acids in the range of C12 to C14. In addition, palm oil is much less saturated than other oils, such as coconut and palm kernel oil. Because palm oil contains roughly equal amounts of saturated and unsaturated fatty acids it can be considered to be a balanced fat.
Palm oil naturally contains carotenes (pro-vitamin A) which give it a red colour. Palm oil carotenoids have alpha-carotene and beta-carotene distribution that is comparable with that of carrots. (The refined red palm oil that is available in some food stores in the US has 15 times the amounts of carotenes compared to carrots and 300 times more than tomatoes). Approximately 1 tablespoon of red palm oil meets 100% of the adult reference dietary intake (RDI). Furthermore, some animal studies have found that carotenoids may have beneficial effects in reducing the risk of cancer and coronary heart disease.
While palm kernel oil and coconut oil have a very similar fatty acid composition, that of palm oil is completely different. Palm kernel oil and coconut oil are rich in lauric acid (hence they are referred to as lauric oils). Palm oil on the other hand has very little lauric acid and is rich in palmitic and oleic acid.
No. Like all vegetable oils, palm oil is cholesterol-free.
Yes. Palm oil is approximately 50% saturated fat and 50% unsaturated fat. This unique characteristic allows palm oil to be separated under controlled thermal conditions into two components: a solid form (palm stearin) and a liquid form (palm olein). This is a type of fractionation process, and may occur in either a dry form or in the presence of a detergent or solvent. Palm stearin is then utilised to form more solid fats, such as margarines, without the need for hydrogenation, thus being trans-free.
Fractionation is a physical method using the crystallisation properties of triglycerides to separate a mixture into a low melting liquid fraction and a high melting liquid fraction. There are three different types of fractionation: dry fractionation, detergent fractionation, and solvent fractionation. Fractionation of palm oil results in two components: palm olein (liquid oil) and palm stearin (solid form).
All fats and oils contain long chain fatty acids. When saturated, the fatty acid chains appear straight and have no kinks. In mono and polyunsaturated fatty acids these chains have double bonds (missing hydrogen atoms), and show bends or kinks at those points where the hydrogen atoms are missing. Hydrogenation adds hydrogen atoms to the double bonds to create a harder, more solid fat.
In order to utilise fats and oils with high percentages of mono and polyunsaturated fatty acids in food processing, manufacturers must first hydrogenate these fats and oils to convert them into a more solid form. Without hydrogenation, many vegetable oils lack the necessary stability to be used in food processing. Foods using unsaturated vegetable oils in their natural state would have a shorter shelf life, could oxidise and become rancid more quickly. They also would not have the same consistency. Unlike many other vegetable oils, palm oil is semi-solid in its natural state and is normally used in food processing without hydrogenation.
Frying is usually performed at 180°C and thus a fat used for frying must be able to withstand high temperatures without adverse chemical changes. Oils high in unsaturated fatty acids as well as those containing large amounts of linoleic and linolenic acid are not suitable for frying due to their tendency to oxidise and break down or polymerise. In the USA, hydrogenated vegetable oils have been the oil of choice for frying. However, these fats contain trans-fatty acids that pose a health concern. Palm oil may be used for frying without the need for hydrogenation, thus serving as trans-free oil for frying. Palm oil is a good frying oil as it contains a moderate level of linoleic acid, negligible amounts of linolenic acid and natural antioxidants.
Palm oil contains equal amounts of saturated and unsaturated fatty acids. The saturated fatty acid portion of palm oil is made up of 44% palmitic acid and 5% stearic acid. The monounsaturated portion of palm oil is composed of oleic acid and accounts for 40% of its composition. 10% of palm oil is made up of the polyunsaturated fatty acid, linoleic acid which is also an essential fatty acid.
Fats and oils are predominantly triesters of fatty acids and glycerol, commonly known as triglycerides. When these appear solid they are referred to as “fats”; when in liquid form, they are called “oils”. All fats are combinations of glycerol and many different fatty acids, each exerting characteristic physiologic and metabolic effects. Fatty acids are generally classified as saturated, monounsaturated or polyunsaturated.
The scientific definition of saturated fat is having every carbon bound to as many hydrogens as possible. Thus the molecule is absent of double bonds. Saturated fat and saturated fatty acids may be used interchangeably. Often saturated fat is used when generalising common characteristics of saturated fatty acids. The length of the carbon chain differentiates saturated fatty acids. The saturated fatty acids commonly found in a typical American diet are lauric acid, myristic acid, palmitic acid and stearic acid. As a rule of thumb, the greater the saturated fat in a food item, the more solid it will be at room temperature. The reverse is also true: the greater the unsaturated fat in a food item, the more liquid it will be at room temperature.
There is scientific evidence that not all saturated fats are equally cholesterol elevating. Studies have found that, compared to other long chain saturated fatty acids, stearic acid appears to have a neutral effect on total cholesterol and low-density lipoprotein (LDL), otherwise known as the “bad” cholesterol. Studies have found that, compared to palmitic acid, lauric acid and myristic acid increase total blood cholesterol, LDL cholesterol (the “bad” cholesterol), high-density lipoprotein (HDL), the ”good” cholesterol, and the LDL/HDL ratio in both nonhuman primates, and normo-cholesterolemic men and women who consumed a typical western diet. The myristic acid and lauric acid from coconut oil increased total blood cholesterol, LDL, HDL, and triglycerides.
Another study found that, in normocholesterolemic primates, dietary palmitic acid and oleic acid produced similar effects on LDL and HDL metabolism. These findings were confirmed in studies with normolipidemic humans who consumed a moderate fat diet low in myristic acid and dietary cholesterol, which found the effect of palmitic acid on total blood cholesterol and LDL/HDL ratio to be comparable to that of oleic acid. Oleic acid is a monounsaturated fatty acid which studies have found to have beneficial effects on total blood cholesterol, LDL, and HDL, in comparison with saturated fats.
Trans fats are created when hydrogenation (taking a liquid fat and turning it into a solid fat by adding hydrogen atoms) is performed. Hydrogenation is used to remove the unsaturation of fatty acids in order to increase the oxidative stability of oils and to raise their melting points. This allows their physical properties to be modified and allows for a broader range of usage in the food industry. Hydrogenated oils are often used in processed foods due to their stability. Since 2006, it has been a requirement to identify trans fats on food labels. A product contains trans fatty acids if a hydrogenated oil is listed under the ”ingredients” section of the food label. Research within the last decade has shown trans fat to have a detrimental effect on cholesterol levels. See also “What are ‘cis’ and ‘trans’ fatty acids?”
Cis and trans describe the typical configurations of hydrogen atoms or groups attached to the carbon atoms involved in a double bond. In the cis configuration they are located on the same side of the plane containing the carbon-to-carbon double bond. During the hydrogenation process, a hydrogen atom may move to the opposite side of the plane containing the double bond. This new configuration is referred to as trans. Though most naturally occurring fatty acids are cis, small quantities of trans fatty acids do occur naturally in ruminant fats and dairy products. Hydrogenated oils are the major source of trans fatty acids.
Extensive research on trans fats (see “What are trans fats?”) has occurred in the past decade. Numerous studies have suggested that trans fat consumption elevates LDL cholesterol (“bad” cholesterol) and decreases the ratio of HDL cholesterol (“good” cholesterol) to LDL cholesterol (a low ratio is desirable). In 1999, a meta-analysis of comparative effects of trans fats versus saturated fats on cholesterol was performed. This study found that as the fat intake increased, the LDL: HDL cholesterol ratio also increased in a dose-dependent manner, and that trans fat consumption increased this ratio more than saturated fat consumption.
The scientific definition of an unsaturated fat is having one or more double bond(s) in the fatty acid chain. There are two types of unsaturated fatty acids:
Monounsaturated fats have only one double bond in the fatty acid chain. The common fatty acid is known as oleic acid. Polyunsaturated fats have two or more double bonds in the fatty acid chain. Some common fatty acids are linoleic acid and linolenic acid, which are essential fatty acids. In general, the more unsaturated a fat, the more liquid it is.
Trans fatty acids are unsaturated fatty acids, (i.e. fatty acids having at least one carbon-carbon double bond) in which the hydrogen atoms are oriented on opposite sides of the carbon-carbon double bond. As a result of this orientation, a relatively straight fatty acid chain results. In contrast, a cis unsaturated fatty acid has the hydrogen atoms oriented on the same side of the carbon-carbon double bond – producing a bend in the fatty acid molecule.
Some trans fatty acids occur naturally and are found in certain meats and dairy products. However, the vast majority of trans fatty acids are produced industrially by a process called hydrogenation. This is a process used to increase the stability of certain liquid vegetable oils, allowing them to be used in a broader range of products. When a liquid vegetable oil is hydrogenated all unsaturated fatty acids are converted to saturated fatty acids. During partial hydrogenation, in addition to saturated fatty acids, trans fatty acids are also formed. A product contains trans fatty acids if the words “partially hydrogenated oil” appear on the food label. By law, trans fatty acids have to be listed on food labels.
Over the last decade or so, extensive research has shown that trans fatty acid consumption, especially the trans fatty acids resulting from partial hydrogenation, are positively linked to higher incidence from certain chronic diseases. There is fairly uniform agreement, that trans fatty acids increase LDL cholesterol levels (“bad” cholesterol) and decrease HDL cholesterol levels (“good” cholesterol). It is believed that trans fatty acids are worse than saturated fatty acids in this regard.