What do oils and fats dissolve in

Last reviewed: March Important functional components of foods, belonging to a group of biological substance called lipids. Fats and oils are soluble in organic solvents such as hexane, petroleum ether, alcohol, and chloroform. They are insoluble in water. Fats and oils have unique properties and play a major role in human nutrition. They add flavor, texture, lubricity, and satiety to foods.

Most fats and oils used for human consumption are plant-derived Fig. The major commodity fats and oils are soybean, cottonseed, canola, sunflower, corn, peanut, palm kernel, and coconut oils; others such as olive, almond, cashew nut, hazelnut, avocado, and sesame oils are considered gourmet or specialty, health-promoting oils.

They are poor conductors of heat and electricity and therefore serve as excellent insulators for the body, slowing the loss of heat through the skin. Fats and oils can participate in a variety of chemical reactions—for example, because triglycerides are esters, they can be hydrolyzed in the presence of an acid, a base, or specific enzymes known as lipases.

The hydrolysis of fats and oils in the presence of a base is used to make soap and is called saponification. Sodium carbonate or sodium hydroxide is then used to convert the fatty acids to their sodium salts soap molecules :.

Ordinary soap is a mixture of the sodium salts of various fatty acids, produced in one of the oldest organic syntheses practiced by humans second only to the fermentation of sugars to produce ethyl alcohol.

Even so, the widespread production of soap did not begin until the s. Soap was traditionally made by treating molten lard or tallow with a slight excess of alkali in large open vats.

The mixture was heated, and steam was bubbled through it. After saponification was completed, the soap was precipitated from the mixture by the addition of sodium chloride NaCl , removed by filtration, and washed several times with water. It was then dissolved in water and reprecipitated by the addition of more NaCl. The glycerol produced in the reaction was also recovered from the aqueous wash solutions.

Pumice or sand is added to produce scouring soap, while ingredients such as perfumes or dyes are added to produce fragrant, colored soaps. Blowing air through molten soap produces a floating soap. Soft soaps, made with potassium salts, are more expensive but produce a finer lather and are more soluble.

They are used in liquid soaps, shampoos, and shaving creams. Dirt and grime usually adhere to skin, clothing, and other surfaces by combining with body oils, cooking fats, lubricating greases, and similar substances that act like glues.

Because these substances are not miscible in water, washing with water alone does little to remove them. Soap removes them, however, because soap molecules have a dual nature. One end, called the head , carries an ionic charge a carboxylate anion and therefore dissolves in water; the other end, the tail , has a hydrocarbon structure and dissolves in oils.

The hydrocarbon tails dissolve in the soil; the ionic heads remain in the aqueous phase, and the soap breaks the oil into tiny soap-enclosed droplets called micelles , which disperse throughout the solution. The droplets repel each other because of their charged surfaces and do not coalesce.

The double bonds in fats and oils can undergo hydrogenation and also oxidation. The hydrogenation of vegetable oils to produce semisolid fats is an important process in the food industry.

Chemically, it is essentially identical to the catalytic hydrogenation reaction described for alkenes. In commercial processes, the number of double bonds that are hydrogenated is carefully controlled to produce fats with the desired consistency soft and pliable. Inexpensive and abundant vegetable oils canola, corn, soybean are thus transformed into margarine and cooking fats. In the preparation of margarine, for example, partially hydrogenated oils are mixed with water, salt, and nonfat dry milk, along with flavoring agents, coloring agents, and vitamins A and D, which are added to approximate the look, taste, and nutrition of butter.

Preservatives and antioxidants are also added. In most commercial peanut butter, the peanut oil has been partially hydrogenated to prevent it from separating out. Consumers could decrease the amount of saturated fat in their diet by using the original unprocessed oils on their foods, but most people would rather spread margarine on their toast than pour oil on it.

Many people have switched from butter to margarine or vegetable shortening because of concerns that saturated animal fats can raise blood cholesterol levels and result in clogged arteries. However, during the hydrogenation of vegetable oils, an isomerization reaction occurs that produces the trans fatty acids mentioned in the opening essay. Chocolate needs to be based on cocoa butter from both a legislative and functionality point of view and any fats used to replace cocoa butter need also to conform to legislation and to melt and crystallise in the same way as cocoa butter.

Often, there is no single natural fat, or even combination of naturally occurring fats, that give the exact functional requirements for a given product application and so oils and fats need to undergo some form of processing. There are three main types of oil modification process used in foods.

Hydrogenation is a reaction between hydrogen and the carbon-carbon double bonds in an unsaturated fatty acid. It changes the cis -unsaturated fatty acid either to saturated or to trans -unsaturated. Both saturated fatty acids and trans -unsaturated fatty acids are higher melting than the naturally occurring cis -unsaturated fatty acids so hydrogenation increases the hardness and solid fat content of the fat.

Fractionation starts with oils that can be partially liquid and partially solid at a particular temperature palm oil, shea butter and palm kernel oil are oils that are commonly fractionated. The solid and liquid phases are separated and used in different applications.

Unlike hydrogenation, no chemical changes to the fatty acids themselves take place — it is purely a separation process. Interesterification is a process in which the ester linkages between the fatty acid and glycerol are broken and then re-formed usually in a random but predictable conformation. However, specific enzymes can be used as catalyst to avoid breaking the ester linkage in the central position of the triglyceride molecule and so allow the production of deliberately structured triglycerides.

Each of these modification processes allow the formation of fats with different melting, crystallisation and stability functionalities from the starting oils. On top of all this, the oils and fats used should give rise to no adverse health concerns. During the course of the 20 th century, hydrogenation was probably the most commonly used modification process.

However, it produces high levels of trans fatty acids. These have been shown to be adverse to health particularly in terms of their effects on blood cholesterol levels. They increase the detrimental low density lipoprotein LDL cholesterol and decrease the beneficial high density lipoprotein HDL cholesterol giving rise to a greater risk of cardiovascular disease CVD in some individuals.

As a consequence of this, the early years of the 21 st century saw widespread reformulation of many food products and the development of non-hydrogenated alternatives to previously hydrogenated fats. Saturated fatty acids are somewhere in the middle — they increase both the detrimental and the beneficial cholesterol levels but they also do this to varying extents depending on their fatty acid chain length.

Lauric C12 , myristic C14 and, to a slightly lesser extent, palmitic C16 acids show an overall adverse effect on blood cholesterol, whereas stearic acid C18 is considered to be neutral in its effects.

These recommendations are largely based on research carried out some 15 years or more ago and recent research has shown a greater leniency towards saturated fats.

Nevertheless, saturated fats should still be used with some caution. One recent example is the fashion for coconut oil. Gunstone FD. Published by Woodhead Publishing, Cambridge. Keywords : Fats, saturated, unsaturated, trans , hydrogenation, fractionation, interesterification, bakery, confectionery, ice cream, frying, blood cholesterol, cardiovascular disease.

Oils and fats are important nutrients in a healthy diet. Structurally, they are esters of glycerol with three fatty acids. As such, they are scientifically called triacylglycerols but are commonly referred to in the food industry as triglycerides.

Although the terms 'oils' and 'fats' are often used interchangeably, they are usually used to distinguish triglycerides in the liquid state at ambient temperatures oils from those in the solid state fats. They are commonly of vegetable origin e. The fatty acids found in most commonly consumed oils and fats are composed of long carbon and hydrogen chains, typically containing from 8 to 20 carbon atoms, mainly with even numbers of carbon atoms, although animal fats also contain significant levels of odd-chain fatty acids.

It is this carboxylic acid group that reacts with the hydroxyl groups on the glycerol molecule to form the ester linkages of the triacylglycerol molecule. Saturated fatty acids are straight chains of carbon atoms consisting of methylene CH2 groups between the end methyl and carboxylic acid groups. The most common saturated fatty acids are lauric acid C12 , palmitic acid C16 and stearic acid C Shorter chain saturated fatty acids are found in butterfat e.

C4, butyric acid and coconut oil e. C8, caprylic acid, and C10, capric acid. Monounsaturated fatty acids contain a single carbon-carbon double bond in the carbon chain. This is usually in the cis configuration. The most common monounsaturated fatty acid is oleic acid, containing 18 carbon atoms. In oleic acid, the double bond is between carbon atoms 9 and 10 counting from the COOH group. Polyunsaturated fatty acids have more than one double bond in the carbon chain.

It is, of course, possible to count the position of these double bonds from the other end of the chain, the methyl group end. In these two examples, the first double bond to be encountered in linoleic acid is at the sixth carbon atom and, for this reason, linoleic acid is also called an omega-6 polyunsaturate. In linolenic acid, the first double bond is at the third carbon atom and so linolenic acid is called an omega-3 polyunsaturate.

The fourth type of fatty acid, trans fatty acids, are also unsaturated but, in this case, some or all of the double bonds are in the trans configuration. As such, they can gradually be produced and build up in used frying oils. However, trans fatty acids are also found naturally in the milk and meat of ruminant animals such as cattle.

The trans fatty acids in milk are mainly vaccenic acid a trans -monounsaturate with a double bond between carbon atoms 11 and 12 and conjugated linoleic acid CLA with a cis double bond between carbon atoms 9 and 10 and a trans double bond between carbon atoms 11 and These fatty acids have not been found to have adverse consequences and may, indeed, be positive.

Increasing the chain length of a fatty acid increases its melting point - so stearic acid C18 melts at a higher temperature than lauric acid C Increasing the number of cis double bonds in a fatty acid decreases its melting point - so, considering the group of fatty acids with 18 carbon atoms, the melting point decreases going from stearic no double bonds to oleic one double bond to linoleic two double bonds to linolenic three double bonds acids.

Changing the double bond configuration from cis to trans increases the melting point - so elaidic acid the trans equivalent of oleic acid has a higher melting point than oleic acid. Different food applications require different melting points and different melting profiles the change in percentage of solid fat with temperature for both processing and sensory functionalities. The ability to have a range of fats and oils available with different physical characteristics is of fundamental importance to food product developers.

However, fatty acids in these different groups and, in some cases, fatty acids within the same group have different nutritional effects, particularly their effects on blood cholesterol levels which, in turn, can impact on cardiovascular disease risk. This will be considered in more detail later in this document. We refer to saturated fats but this only says that they are naturally occurring fats in which saturated fatty acids predominate.

The same thing can be said about monounsaturated fats, polyunsaturated fats and trans fats. Different food applications require fats with different functionalities and, therefore, different fatty acid compositions. These different requirements for specific applications will be considered in more detail in a later section.

Sometimes, the requirements can be completely fulfilled by a naturally occurring fat or a combination of naturally occurring fats. For example, chocolate can be made purely from cocoa butter or, in the case of milk chocolate, from cocoa butter and butterfat. In some applications, though, the portfolio of fats as they occur in nature do not totally fulfil the functional requirements and so the fats need to undergo some kind of processing to obtain the required functionality.

One of the earliest oil processing methods was hydrogenation List and King, In the presence of a catalyst usually nickel the double bonds in a liquid oil can react with hydrogen in two ways.

Either a hydrogen molecule can react with the carbon atoms in an unsaturated bond to convert it into a saturated single bond.

This has a higher melting point and so a liquid oil can be converted into a solid fat.