Lipid
Lipids are a broad group of naturally occurring molecules which includes fats,waxes, sterols, fat-soluble vitamins and others. The main
biological functions of lipids include energy storage, as structural components of cell membranes, and as important signaling molecules.Lipids consists of two part. One is hydrophilic that is water soluble and other is hydrophobic that is water non soluble.
FATS & OILS
Fats and oils are composed of the elements carbon, hydrogen, and oxygen in the form of glycerides or compounds of fatty acids and glycerol. Fats and oils belong to a group of biological substances called lipids. Lipids are biological chemicals that do not dissolve in water. They serve a variety of functions in organisms, such as regulatory messengers (hormones), structural components of membranes, and as energy storehouses. Fats and oils generally function in the latter capacity.
Fats and oils are actually both triglycerides. Fats are generally solids and oils are generally liquids at ordinary room temperatures.
CH2—OH CH2 COOR
CH2—OH +
3HO—COR à CH2 COOR +
3H2O
CH2—OH CH2 COOR
Sources
of fats and oils:
Fats and oils are mostly obtained from animals and plants.
fats are obtained from the adipose tissues of animals. More or less of it occurs in the muscles, in the connective tissue, under the skin, and in the bones. The fats from the different parts and organs of a given animal differ somewhat in their properties. As a rule, the fat from the interior of the animal is somewhat firmer than the fat from near the body surface, i.e., it melts at a somewhat higher temperature. Vegetable fats and oils are found in greatest abundance in fruits and seeds. While fats and oils do occur in the roots, stalks, branches, and leaves of plants, they are rarely present in these organs in quantities large enough for commercial purposes. In some seeds and fruits, however, the fat content is great -- in several cases as high as 35 per cent; in dried coconuts 65 per cent -- and these
are the commercial sources of vegetable fats. In some seeds the fat is practically confined to the germ or embryo; this is the fact in most of the cereals.
fats are obtained from the adipose tissues of animals. More or less of it occurs in the muscles, in the connective tissue, under the skin, and in the bones. The fats from the different parts and organs of a given animal differ somewhat in their properties. As a rule, the fat from the interior of the animal is somewhat firmer than the fat from near the body surface, i.e., it melts at a somewhat higher temperature. Vegetable fats and oils are found in greatest abundance in fruits and seeds. While fats and oils do occur in the roots, stalks, branches, and leaves of plants, they are rarely present in these organs in quantities large enough for commercial purposes. In some seeds and fruits, however, the fat content is great -- in several cases as high as 35 per cent; in dried coconuts 65 per cent -- and these
are the commercial sources of vegetable fats. In some seeds the fat is practically confined to the germ or embryo; this is the fact in most of the cereals.
Composition of Fats and Oils
Fat and oil glyceride molecules can contain a single fatty acid species or any combination of up to three fatty acids. The fats r oils that contains the same (only one) fatty acids are called Simple fats and oils, but the fatty acids in fats and oils are different then the fats and oils are known as mixed fats r oils. Most naturally occurring fat and oil molecules contain a combination of fatty acids. The chemical composition of fats and oils is given as
§ Esters (Tri Acycle Glycerol)…..90%
§ Free fatty acids, Phospholipids, Cholesterol
are present about 10%
§ Other traces are Pigments, Steroids and etc
Essential Fats:
Essential fats contain fatty acids and are polyunsaturated fatty acids (PUFAs), they are essential to human health. They cannot be synthesized or made by the human body so they must be obtained from our diet. There are two families of essential fatty acids Omega-3 and Omega-6. Omega-9 is necessary yet "non-essential" because the body can manufacture a modest amount on its own, provided essential fatty acids are present. Every cell in our bodies depends on them for proper function and survival. Our bodies and our brain in particular, are to a degree made up of them. These essential fatty acids are responsible for a myriad of functions in the body. Many of us are deficient in these fatty acids especially Omega-3.
Physical
properties:
Saturated and unsaturated fats and oils:
If the fat or oil is saturated, it means that the acid that it was derived from has no carbon-carbon double bonds in its chain. Stearic acid is a saturated acid, and so glyceryl tristearate is a saturated fat.
If the acid has just one carbon-carbon double bond somewhere in the chain, it is called mono-unsaturated. If it has more than one carbon-carbon double bond, it is polyunsaturated. All of these are saturated acids, and so will form saturated fats and oils:
If the fat or oil is saturated, it means that the acid that it was derived from has no carbon-carbon double bonds in its chain. Stearic acid is a saturated acid, and so glyceryl tristearate is a saturated fat.
If the acid has just one carbon-carbon double bond somewhere in the chain, it is called mono-unsaturated. If it has more than one carbon-carbon double bond, it is polyunsaturated. All of these are saturated acids, and so will form saturated fats and oils:
Oleic acid is a typical mono-unsaturated acid:
. . . and linoleic and linolenic acids are typical polyunsaturated acids.
Linoleic acid is an omega 6 acid. It just means that the first carbon-carbon double bond starts on the sixth carbon from the CH3 end. Ilinolenic acid is an omega 3 acid for the same reason.
Specific gravity:
Specific gravity of fats and iols is less than that of water, therefore they can float on the surface of water. This principle is used in solvent extraction to separate many dissolved parts of the mixture.Conductivity:Fats and oils are very poor conductor of electricity and heat, therefore serves as insulation of the body of animals.
Solubility in water:None of these molecules are water soluble. The chain lengths are now so great that far too many hydrogen bonds between water molecules would have to be broken - so it isn't energetically profitable.
Melting points:
The melting points determine whether the substance is a fat (a solid at room temperature) or an oil (a liquid at room temperature).Fats normally contain saturated chains. These allow more effective van der Waals dispersion forces between the molecules. That means you need more energy to separate them, and so increases the melting points.The greater the extent of the unsaturation in the molecules, the lower the melting points tend to be because the van der Waals dispersion forces are less effective. van der Waals dispersion forces need the molecules to be able to pack closely together to be really effective. The presence of carbon carbon double bonds in the chains gets in the way of tidy packing.
Here is a simplified diagram of a saturated fat:
If they are on opposite sides of the double bond (the trans form) the effect isn't as marked.
A polyhydrogenated fat is one that has been altered by such a reaction. The reaction may cause the oil to become a solid. Margarine and shortening are vegetable-based oils that have undergone partial hydrogenation.The peanut oil in peanut butter usually has been hydrogenated to prevent it from separating. Another product of partial hydrogenation is a class of fats called trans fatty acids. Foods high in trans fatty acids (for example, margarine, shortening, and commercially fried food) tend to raise cholesterol levels in the blood.
The hydrocarbon chains are, of course, in constant motion in the liquid, but it is possible for them to lie tidily vwhen the substance solidifies. If the chains in one molecule can lie tidily,that means that neighbouring molecules can get close. That increases the attractions between one molecule and its neighbours and so increases the melting point. Unsaturated fats and oils have at least one carbon-carbon double bond in at least one chain.
There isn't any rotation about a carbon-carbon double bond and so that locks a permanent kink into the chain. That makes packing molecules close together more difficult. If they don't pack so well, the van der Waals forces won't work as well. This effect is much worse for molecules where the hydrocarbon chains either end of the double bond are arranged cis to each other - in other words, both of them on the same side of the double bond:
There isn't any rotation about a carbon-carbon double bond and so that locks a permanent kink into the chain. That makes packing molecules close together more difficult. If they don't pack so well, the van der Waals forces won't work as well. This effect is much worse for molecules where the hydrocarbon chains either end of the double bond are arranged cis to each other - in other words, both of them on the same side of the double bond:
 Trans fats and oils have higher melting points than cis ones because the packing isn't affected quite as much. Naturally occurring unsaturated fats and oils tend to be the cis form. | |
Differences between fats and
oils:
Animal and vegetable fats and oils are just big complicated esters. The difference between a fat (like butter) and an oil (like sunflower oil) is simply in the melting points of the mixture of esters they contain.If the melting points are below room temperature, it will be a liquid - an oil. If the melting points are above room temperature, it will be a solid - a fat. The causes of the differences in melting points will be discussed further down the page under physical properties.
Properties
And Uses:
·
The properties of fats will differ according to the properties of the fatty acids of which they are composed. The ratio of carbon and hydrogen to oxygen in the fat molecule, however, is much greater than that in a carbohydrate. As an example, a fat found in beef that is tristearin has 110 atoms of hydrogen to 6 atoms of oxygen, as compared to the two-to-one ratio of the same elements in the carbohydrate glucose. The chemical term for a fat is triglyceride. All food fats are mixtures of glycerides and variation in mixtures accounts for the wide variation in consistency, flavor, and chemical properties of various food fats
· Fats and oils play an important role in human nutrition because they are sources of energy and of the essential fatty acids in the diet.
· Fat deposits in the body serve as insulation and provide protective cushions for the organs.
· Fats are the most concentrated form of energy in foods, yielding more than twice as much energy as equal portions of either carbohydrates or proteins.
· Fats are known to protect the body in two ways. The deposits of fat under the skin act as nonconductors of heat, helping to insulate the body and prevent the rapid loss of heat. Furthermore, the viscera and certain organs of the body, such as the kidneys, are supported and cushioned by fat.
· In the pure form one pound of fat yields about 4,000 calories that is more than two times the calories furnished by an equal quantity of protein or carbohydrate.
· Fats are also valuable for the flavor, richness, and satiety quality that they give to meals.
· Some fats and oils contain fatty acids essential for good nutrition and some fats are sources of the fat soluble vitamins A, D, and E. Refined vegetable oils and hydrogenated fat contain little or no vitamin A although in their natural state some yellow-colored vegetable oils may contain appreciable amounts
· They serve a variety of functions in organisms, such as regulatory messengers (hormones), structural components of membranes, and as energy storehouses.
· All cheeses except for cottage cheese contain appreciable amounts of the nutrient. The fat in an egg is found only in the yolk. Most fruits and vegetables contain little fat; however, avocados and coconuts, which contain about 20 per cent fat, are exceptions.
The properties of fats will differ according to the properties of the fatty acids of which they are composed. The ratio of carbon and hydrogen to oxygen in the fat molecule, however, is much greater than that in a carbohydrate. As an example, a fat found in beef that is tristearin has 110 atoms of hydrogen to 6 atoms of oxygen, as compared to the two-to-one ratio of the same elements in the carbohydrate glucose. The chemical term for a fat is triglyceride. All food fats are mixtures of glycerides and variation in mixtures accounts for the wide variation in consistency, flavor, and chemical properties of various food fats
· Fats and oils play an important role in human nutrition because they are sources of energy and of the essential fatty acids in the diet.
· Fat deposits in the body serve as insulation and provide protective cushions for the organs.
· Fats are the most concentrated form of energy in foods, yielding more than twice as much energy as equal portions of either carbohydrates or proteins.
· Fats are known to protect the body in two ways. The deposits of fat under the skin act as nonconductors of heat, helping to insulate the body and prevent the rapid loss of heat. Furthermore, the viscera and certain organs of the body, such as the kidneys, are supported and cushioned by fat.
· In the pure form one pound of fat yields about 4,000 calories that is more than two times the calories furnished by an equal quantity of protein or carbohydrate.
· Fats are also valuable for the flavor, richness, and satiety quality that they give to meals.
· Some fats and oils contain fatty acids essential for good nutrition and some fats are sources of the fat soluble vitamins A, D, and E. Refined vegetable oils and hydrogenated fat contain little or no vitamin A although in their natural state some yellow-colored vegetable oils may contain appreciable amounts
· They serve a variety of functions in organisms, such as regulatory messengers (hormones), structural components of membranes, and as energy storehouses.
· All cheeses except for cottage cheese contain appreciable amounts of the nutrient. The fat in an egg is found only in the yolk. Most fruits and vegetables contain little fat; however, avocados and coconuts, which contain about 20 per cent fat, are exceptions.
Chemical
properties:
Hydrogenation:
Vegetable oils, with their higher degrees of unsaturation, can be converted to solids via reaction with hydrogen in a process called hydrogenation. The hydrogenation process involves "sparging" the oil at high temperature and pressure with hydrogen in the presence of a catalyst, typically a powdered nickel compound. As each carbon-carbon double-bond is chemically reduced to a single bond, two hydrogen atoms each form single bonds with the two carbon atoms.A polyhydrogenated fat is one that has been altered by such a reaction. The reaction may cause the oil to become a solid. Margarine and shortening are vegetable-based oils that have undergone partial hydrogenation.The peanut oil in peanut butter usually has been hydrogenated to prevent it from separating. Another product of partial hydrogenation is a class of fats called trans fatty acids. Foods high in trans fatty acids (for example, margarine, shortening, and commercially fried food) tend to raise cholesterol levels in the blood.
Saponification:
Because fats and oils are triesters of glycerol, they react with water to form fatty acids and glycerin. When the reaction is carried out in a basic solution, salts of the fatty acids are produced instead of the fatty acids themselves. The salts of fatty acids are soaps and an individual molecule is characterized by an ionic end (the salt part) and a nonpolar end (the hydrocarbon part). The ionic salt end is water-soluble and the nonpolar hydrocarbon end is water insoluble. The process of making soaps by treating fats and oils with basic substances is called saponification (which means "soapmaking").
Saponification number:
The saponification number is defined as the number of milligrams of potassium hydroxide needed to saponify completely one gram of a fat or an oil. One mole of fat requires three moles of potassium hydroxide for complete saponification. If a fat contains fatty acids of relatively high molecular weights, then one gram of the fat will consist of fewer moles. Thus, fats having greater percentages of high molecular weight fatty acids will have lower saponification numbers than fats having greater percentages of lower molecular weight fatty acids. Lard, which contains mostly 16– and 18–carbon fatty acids, has a saponification number range of 190 to 200. Coconut oil, which is about 50 percent lauric acid, a 12–carbon fatty acid, has a saponification number approaching 260.
The saponification number is defined as the number of milligrams of potassium hydroxide needed to saponify completely one gram of a fat or an oil. One mole of fat requires three moles of potassium hydroxide for complete saponification. If a fat contains fatty acids of relatively high molecular weights, then one gram of the fat will consist of fewer moles. Thus, fats having greater percentages of high molecular weight fatty acids will have lower saponification numbers than fats having greater percentages of lower molecular weight fatty acids. Lard, which contains mostly 16– and 18–carbon fatty acids, has a saponification number range of 190 to 200. Coconut oil, which is about 50 percent lauric acid, a 12–carbon fatty acid, has a saponification number approaching 260.
Rencidification:
Fats and oils are quite unstable substances. When stored for any considerable length of time, especially when the temperature is high and the air has free access to them, they deteriorate and spoil. In this respect different fats differ markedly. Some spoil very much more rapidly than others. The fat acquires a peculiarly disagreeable odor and flavor. This fact is called rencidification or rancidity of fats and oils. This is due to axidation and deterioration of fats and oils.
Industrial application of fats and oils:
In food
Many vegetable oils are consumed directly, or indirectly as ingredients in food - a role that they share with some animal fats, including butter and ghee. The oils serve a number of purposes in this role:
Industrial application of fats and oils:
In food
Many vegetable oils are consumed directly, or indirectly as ingredients in food - a role that they share with some animal fats, including butter and ghee. The oils serve a number of purposes in this role:
- Shortening - to give pastry a crumbly texture.
- Texture - oils can serve to make other ingredients stick together less.
- Flavor - while less-flavorful oils command premium prices, some oils, such as olive, sesame or almond oil, may be chosen specifically for the flavor they impart.
- Flavor base - oils can also "carry" flavors of other ingredients, since many flavors are present in chemicals that are soluble in oil.
- Secondly, oils can be heated, and used to cook other foods. Oils suitable for this purpose must have a high flash point. Such oils include the major cooking oils - soy, canola, sunflower, safflower, peanut, cottonseed, etc.
- Vegetable oils are used as an ingredient or component in many manufactured products.
- Many vegetable oils are used to make soaps, skin products, candles, perfumes and other personal care and cosmetic products.
- Some oils are particularly suitable as drying oils, and are used in making paints and other wood treatment products.
- Vegetable oils are increasingly being used in the electrical industry as insulators as vegetable oils are not toxic to the environment, biodegradable if spilled and have high flash and fire points
- One limiting factor in industrial uses of vegetable oils is that all such oils eventually chemically decompose, turning rancid. Oils that are more stable, such as ben oil or mineral oil, are preferred for some industrial uses.
