Hydrogenation Of Fats And Oils Pdf
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Advice service. Oils such as vegetable, olive, sunflower are liquids at room temperature.
- Hydrogenation of Edible oils
- Hydrogenation of Fats and Oils
- 12.4: Application: Hydrogenation of Oils
Hydrogenation of Edible oils
For many edible purposes and for some commercial applications it is desirable to produce solid fats. Many shortenings and margarines contain hydrogenated hardened oils as their major ingredients. The development of margarine and shortening products resulted from the invention of a successful method for converting low-melting unsaturated fatty acids and glycerides to higher-melting saturated products.
The process consists of the addition of hydrogen in the presence of a catalyst to the double unsaturated bonds. Thus oleic or linoleic acid or their acid radicals in glycerides , which are normally liquid at room temperature, can be converted to stearic acid or the acid radical by the addition of hydrogen.
Limited use was made of this hydrogenation technology in Europe; the greatest potential use for the process lay in the United States, where a vast production of cottonseed oil, a by-product of the Southern cotton industry, awaited developments that would permit its conversion to a plastic fat. The hardening of cottonseed oil in the early s gave birth to the shortening industry. Practical hydrogenation then spread to all countries where margarines and shortenings are produced from liquid oils.
In commercial practice, hydrogenation is usually carried out with vigorous agitation or hydrogen dispersion with a narrow range of catalyst concentration about 0. These conditions can be controlled to make the hydrogenation reaction somewhat selective— i.
The most unsaturated fatty acid groups are most easily hydrogenated and thus react first with the hydrogen if conditions are right. Copper-containing catalysts are especially selective in the hydrogenation of vegetable oils. If very hard fats with low amounts of unsaturation are desired and selectivity is unimportant, higher temperatures and pressures are employed to shorten the reaction time and to use partially spent catalyst that would otherwise be wasted.
After hydrogenation, the hot oil is filtered to remove the metallic catalyst for either reuse or recovery. During the catalytic treatment another reaction also takes place—isomerization rearrangement of the molecular structure of unsaturated fatty acid radicals to form isooleic, isolinoleic, and similar groups.
Because these isomers have higher melting points than do the natural acids, they contribute to the hardening effect. The unsaturation of natural oils has the cis configuration, in which hydrogen atoms lie on one side of a plane cutting through the double bond and alkyl groups lie on the other side.
During hydrogenation some of the unsaturation is converted to the trans configuration, with like groups on opposite sides of the plane. The trans isomers are much higher melting than the natural cis form.
Simultaneously with the change of some of the unsaturation to the trans configuration there is a migration of double bonds along the chain. Thus isomers of oleic acid may be formed with the double bond in any position from carbon atom 2 to carbon atom Many of these isomerized acids are higher melting than the natural oleic acid.
Infrared analysis is useful for quantitative measurement of changes occurring during hydrogenation. Odourless and tasteless fats first came into high demand as ingredients for the manufacture of margarine, a product designed to duplicate the flavour and texture of butter. Most fats, even after refining, have characteristic flavours and odours, and vegetable fats especially have a relatively strong taste that is foreign to that of butter.
The deodorization process consists of blowing steam through heated fat held under a high vacuum. Small quantities of volatile components, responsible for tastes and odours, distill, leaving a neutral, virtually odourless fat that is suitable for the manufacture of bland shortening or delicately flavoured margarine.
Originally, deodorization was a batch process, but increasingly, continuous systems are being used in which hot fat flows through an evacuated column countercurrent to the upward passage of steam. About 0. Olive oil is invariably marketed in undeodorized form. The natural flavour is an important asset, and olive oil , as is true of butter, commands a premium in the market because of its distinctive and prized flavour. The common cooking oils of Asia—soybean, rapeseed, peanut, sesame, and coconut—are consumed in their crude form as expressed from oilseeds.
In contrast, deodorized oils are in particular demand in the United States and Europe. For many years the only important vegetable oil consumed in the United States was cottonseed oil, which in its crude form has such a strong and unpleasant flavour that further processing was an absolute necessity in order to render it suitable for consumption. Because of widespread sale of neutral-flavoured cottonseed oil products over many years, a general preference was developed for odourless and tasteless fats.
Another reason for the practice of deodorizing edible oils in Europe and America relates to differences in oil quality by Western and Eastern extraction techniques.
In China and Southeast Asia , edible oils have been produced principally by small, relatively crude equipment. The yield of oil is relatively low, and a minimum amount of nonglyceride substances is expressed from the seed, with the result that the flavour of the oil is fairly mild.
In Europe and the United States, oil extraction is carried out in large factories that operate on an extremely competitive basis. Very-high-pressure expression or solvent extraction is used, and in order to improve yields the seeds are heat-treated prior to extraction.
Oils obtained in high yield under such conditions are stronger in flavour than oils prepared by low-pressure expression, and the refining and deodorizing steps are required to improve palatability. The improvement in yields more than compensates for the added costs of refining and deodorizing.
Fat and oil processing Article Media Additional Info. Article Contents. Load Previous Page. Hydrogenation For many edible purposes and for some commercial applications it is desirable to produce solid fats. Hydrogenation reactions In commercial practice, hydrogenation is usually carried out with vigorous agitation or hydrogen dispersion with a narrow range of catalyst concentration about 0.
Isomerization reactions During the catalytic treatment another reaction also takes place—isomerization rearrangement of the molecular structure of unsaturated fatty acid radicals to form isooleic, isolinoleic, and similar groups. Deodorization Odourless and tasteless fats first came into high demand as ingredients for the manufacture of margarine, a product designed to duplicate the flavour and texture of butter.
Richard Baldwin Marvin W. Fats, in the form of triglycerides, accumulate in the fat cells found in and around the muscles of the animal. Fat deposits that surround the muscles are called adipose tissue, while fat that is deposited between the fibres of a muscle is called marbling. A high fat content within the adipose tissue and marbling sites of muscle contributes to the tenderness of the meat. During the cooking process the fat melts into a lubricant-type substance that spreads throughout the meat, increasing the tenderness of the final product.
A negligible quantity of protein is found in fruits, and they usually contain less than 1 percent fat. Fats are most typically associated with the waxy cuticle surface of the fruit skin.
Exceptions to this rule are avocados and olives, the flesh of…. History at your fingertips. Sign up here to see what happened On This Day , every day in your inbox! Email address. By signing up, you agree to our Privacy Notice. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.
Hydrogenation of Fats and Oils
The physical properties of oils and fats depend on their chemical properties, such as unsaturation, saturation, chain length, and distribution of the three hydroxyl groups of glycerol in the fatty acids. These characteristics change by hydrogenation, fractionation, blending, and interesterification IE , hence improving the spectrum for the application of the oils and fats. IE is a process where the fatty acids have been moved from one triglyceride molecule to another and it does not alter the fatty acids. IE chemical and enzymatic is used to deal with the problems of plastic fat products such as granular development, texture breakdown, lumpy appearance, post hardening, consistency, melting point, and rancidity and create oil more suitable for deep frying or making margarine with good taste and low content of saturated fatty acids, etc. Nutritionally, IE contributes in eliminating or reducing trans fatty acids, providing a higher essential fatty acid activity.
The supply and demand of edible oils and fats is briefly reviewed, and certain trends, relevant for the application of fat modification techniques, are noted. The effect of hydrogenation conditions on a number of selectivity aspects in hydrogenation with nickel catalysts is explained in terms of mass transport effects for hydrogen and triglycerides. The effect of selectivity on stability and melting behavior is also discussed. The limitations of the existing hydrogenation process with nickel are pointed out, and possible extensions by use of other catalysts, such as sulphur poisoned nickel, copper, and chromium complexes, are mentioned. Some technological aspects of the process are briefly reviewed.
12.4: Application: Hydrogenation of Oils
Vegetable oils , or vegetable fats , are oils extracted from seeds or, less often, from other parts of fruits. Like animal fats , vegetable fats are mixtures of triglycerides. Olive oil , palm oil , and rice bran oil are examples of fats from other parts of fruits. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature. Oils extracted from plants have been used since ancient times and in many cultures.
Food companies began using hydrogenated oil to help increase shelf life and save costs. Hydrogenation is a process in which a liquid unsaturated fat is turned into a solid fat by adding hydrogen.
Roslyn B. Alfin-Slater, Arthur F. Wells, Lilla Aftergood, Harry J. Deuel, Jr.
In nutrition , biology , and chemistry , fat usually means any ester of fatty acids , or a mixture of such compounds ; most commonly those that occur in living beings or in food. The term often refers specifically to triglycerides triple esters of glycerol , that are the main components of vegetable oils and of fatty tissue in animals;  or, even more narrowly, to triglycerides that are solid or semisolid at room temperature, thus excluding oils. The term may also be used more broadly as a synonym of lipid -- any substance of biological relevance, composed of carbon , hydrogen , or oxygen , that is insoluble in water but soluble in non-polar solvents.
Hydrogenation of vegetable oils has been practiced since the discovery by Normann some 75 years ago and is the major chemical process in the fat and oil industry. Hydrogenation changes a liquid oil to a semisolid fat which has more utility and better flavor stability. The reaction is not a simple saturation of double bonds with hydrogen, but is an extremely complex series of reactions that result in a myriad of products. By control of the reaction conditions, pressure, temperature, agitation, and catalyst type and concentration, the desired product may be obtained. The use of new equipment and methods has produced some understanding of the hydrogenation reactions.