Basic integral part fats of animal and vegetable origin are esters of trihydric alcohol - glycerol and fatty acids, called glycerides(acylglycerides). Fatty acids are included not only in glycerides, but also in most other lipids.

The variety of physical and chemical properties of natural fats is due to the chemical composition of fatty acids of glycerides. The composition of triglycerides of fats includes various fatty acids. At the same time, depending on the type of animal or plant from which the fats are obtained, the fatty acid composition of triglycerides is different.

The composition of glycerides of fats and oils includes mainly high molecular weight fatty acids with the number of carbon atoms of 16.18, 20.22 and above, low molecular weight with the number of carbon atoms 4, 6 and 8 (butyric, caproic and caprylic acids). The number of acids isolated from fatty acids reaches 170, but some of them are still insufficiently studied and information about them is very limited.

The composition of natural fats includes saturated (marginal) and unsaturated (unsaturated) fatty acids. Unsaturated fatty acids can contain double and triple bonds. The latter are very rare in natural fats. As a rule, natural fats contain only monobasic carboxylic acids with an even number of carbon atoms. Dibasic acids are isolated in small amounts in some waxes and in fats that have been exposed to oxidizing agents. The vast majority of fatty acids in fats have an open chain of carbon atoms. Branched-chain acids are rare in fats. Such acids are part of some waxes.

Fatty acids of natural fats are liquid or solid, but fusible substances. High molecular weight saturated acids are solid, most unsaturated fatty acids of a normal structure are liquid substances, and their positional and geometric isomers are solid. The relative density of fatty acids is less than unity and they are practically insoluble in water (with the exception of low molecular weight ones). In organic solvents (alcohol, ethyl and petroleum ethers, benzene, carbon disulfide, etc.), they dissolve, but with an increase in molecular weight, the solubility of fatty acids decreases. Hydroxy acids are practically insoluble in petroleum ether and cold gasoline, but soluble in ethyl ether and alcohol.

Of great importance in the refining of oils and in soap making is the reaction of interaction of caustic alkalis and fatty acids - the neutralization reaction. When sodium or potassium carbonate acts on fatty acids, an alkaline salt or soap is also obtained with the release of carbon dioxide. This reaction takes place in the process of making soap with the so-called carbonate saponification of fatty acids.

Fatty acids of natural fats, with rare exceptions, belong to the class of monobasic aliphatic carboxylic acids having the general formula RCOOH. In this formula, R is a hydrocarbon radical, which can be saturated, unsaturated (of varying degrees of unsaturation) or contain a group - OH, COOH - carboxyl. Based on X-ray diffraction analysis, it has now been established that the centers of carbon atoms in the chain of fatty acid radicals are spatially located not in a straight line, but in a zigzag pattern. In this case, the centers of all carbon atoms of saturated acids fit on two parallel straight lines.

The length of the hydrocarbon radical of fatty acids affects their solubility in organic solvents. For example, the solubility at 20 ° C in 100 g of anhydrous ethyl alcohol of lauric acid is 105 g, myristic acid is 23.9 g, and stearic acid is 2.25 g.

Isomerism of fatty acids. Under isomerism understand the existence of several chemical compounds of the same composition and the same molecular weight, but differing in physical and chemical properties. Two main types of isomerism are known: structural and spatial (stereoisomerism).

Structural isomers differ in the structure of the carbon chain, the arrangement of double bonds and the arrangement of functional groups.

An example of structural isomers are compounds:

a) different in the structure of the carbon chain: normal butyric acid CH 3 CH 2 CH 2 COOH; isobutyric acid

b) different in the arrangement of double bonds: oleic acid CH 3 (CH 2) 7 CH \u003d CH (CH 2) 7 COOH; petroselinic acid CH 3 (CH 2) 10 CH=CH(CH 2) 4 COOH; vaccenic acid CH 3 (CH 2) 5 CH \u003d CH (CH 2) 8 COOH.

Spatial isomers, or stereoisomers, with the same structure, differ in the arrangement of atoms in space. This type of isomers includes geometric (cis- and trans-isomers) and optical. An example of spatial isomers are:

a) geometric isomers: oleic acid having a cis form

elaidic acid, which has a transform

b) optical isomers:

lactic acid CH 3 CHOHCOOH;

glyceraldehyde CH 3 ONSNO;

ricinoleic acid CH3 (CH 2) 5 CHOHCH 2 CH \u003d CH (CH 2) 7 COOH.

All of these optical isomers have an asymmetric (active) carbon marked with an asterisk.

Optical isomers rotate the plane of polarization of light by the same angle in opposite directions. Most natural fatty acids do not have optical isomerism.

In natural fats that have not undergone oxidative processes, unsaturated fatty acids are mainly in the cis configuration. The geometric cis- and trans-isomers of unsaturated fatty acids differ significantly in their melting points. The cis isomers melt at a lower temperature than the trans isomers. This is clearly illustrated by the cis-trans conversion of liquid oleic acid to solid elaidic acid (melting point 46.5°C). In this case, the fat hardens.

The same transformation occurs with erucic acid, which turns into a solid trans isomer - brassidic acid (melting point 61.9 ° C), as well as ricinoleic acid, which turns into a trans isomer - racinelaidic acid (melting point 53 ° C).

Polyunsaturated fatty acids (linoleic, linolenic) do not change the consistency during this reaction.

In natural fats that have not undergone oxidative processes, the following main homologous groups of fatty acids are found:

1. Saturated (limiting) monobasic acids.

2. Unsaturated (unsaturated) monobasic acids with one, two, three, four and five double bonds.

3. Saturated (limiting) hydroxy acids.

4. Unsaturated (unsaturated) hydroxy acids with one double bond.

5. Dibasic saturated (limiting) acids.

6. Cyclic acids.

Isomers are compounds that have the same chemical composition but different molecular structures. Isomerization of fats and oils can occur in several ways:

Isomerism according to the position in the triglceride. This type of isomerism is a rearrangement of fatty acids in a glycerol molecule. This rearrangement usually occurs upon transesterification, but may also occur upon thermal treatment. Altering the position of the fatty acid in triglyceride can affect the shape of the crystals, the melting characteristics, and the metabolism of lipids in the body.

Position isomerism. Unsaturated fatty acids can isomerize in acidic or alkaline environments, as well as when exposed to high temperatures, by migrating the double bond from positions 9 and 12 to others, for example, positions 9 and 10, 10 and 12, or 8 and 10. the double bond on the new position is lost, fatty acids cease to be essential.

Spatial isomerism, the double bond can have two configurations: cis- or trans-form. Natural fats and oils usually contain cis-isomers of fatty acids, which are the most reactive and require relatively little energy to convert to trans-isomers. Trans isomers are characterized by tighter packing of molecules, allowing them to behave like saturated fatty acids with a high melting point. From a nutritional hygiene point of view, trans fatty acids are considered analogous to saturated fatty acids, both of which can cause an increase in LDL cholesterol in the circulatory system. 7Range fatty acids are formed at very high temperatures, predominantly during hydrogenation and, to a lesser extent, during deodorization. The content of /rance-isomers in hydrogenated soybean and rapeseed oils can reach 55%, the isomers are predominantly represented by trans-elaidic (C,.,) acid, since almost all linolenic (C1v.3) and linoleic (C, x 2) acids hydrogenated to fatty acids C)K |. Isomerism caused by thermal effects, especially affecting linolenic

18 "h) acid and, to a lesser extent, fatty acid Clg 2, depends on the temperature and duration of exposure. In order for the formation of trPNs isomers not to exceed 1%, the deodorization temperature should not exceed 240 ° C, the duration of treatment is 1 hour, higher temperatures can> be used with a shorter exposure time.

Conjugated linoleic fatty acids (CLA). CLA is a natural isomer of linoleic acid (C|R2) in which the two double bonds are conjugated and located at carbon atoms 9 and 11 or 10 and 12, with a possible combination of cis and trans isomers. CI.A usually produce. etsya anaerobic bacteria of the rumen of cattle during biohydrogenation. Recent international medical research has shown that CLA may have properties beneficial to human health, such as anti-tumorogenic1 and anti-atherogenic2.

Esters can be considered as derivatives of acids in which the hydrogen atom in the carboxyl group is replaced by a hydrocarbon radical:

Nomenclature.

Esters are named after acids and alcohols, the residues of which are involved in their formation, for example H-CO-O-CH3 - methyl formate, or formic acid methyl ester; - ethyl acetate, or ethyl ester of acetic acid.

Ways to get.

1. Interaction of alcohols and acids (esterification reaction):

2. Interaction of acid chlorides and alcohols (or alkali metal alcoholates):

physical properties.

Esters of lower acids and alcohols are liquids lighter than water, with a pleasant smell. Only esters with the smallest number of carbon atoms are soluble in water. Esters are readily soluble in alcohol and distyl ether.

Chemical properties.

1. Hydrolysis of esters is the most important reaction of this group of substances. Hydrolysis under the action of water is a reversible reaction. Alkalis are used to shift the equilibrium to the right:

2. The reduction of esters with hydrogen leads to the formation of two alcohols:

3. Under the action of ammonia, esters are converted into acid amides:

Fats. Fats are mixtures of esters formed by the trihydric alcohol glycerol and higher fatty acids. General formula for fats:

where R - radicals of higher fatty acids.

The most common fats are saturated palmitic and stearic acids and unsaturated oleic and linoleic acids.

Getting fat.

Currently, only obtaining fats from natural sources of animal or vegetable origin is of practical importance.

physical properties.

Fats formed by saturated acids are solids, and unsaturated fats are liquid. All are very poorly soluble in water, soluble in diethyl ether.

Chemical properties.

1. Hydrolysis, or saponification of fats occurs under the action of water (reversible) or alkalis (irreversible):

Alkaline hydrolysis produces salts of higher fatty acids called soaps.

2. Hydrogenation of fats is the process of adding hydrogen to the residues of unsaturated acids that make up fats. In this case, the residues of unsaturated acids turn into residues of saturated acids, and fats from liquids turn into solids.

Of the most important nutrients - proteins, fats and carbohydrates - fats have the largest energy reserve.

Lesson number 45. Fats, their structure, properties and applications

"Chemistry everywhere, chemistry in everything:

In everything we breathe

In everything we drink

Everything we eat."

In everything we wear

People have long learned to isolate fat from natural objects and use it in Everyday life. Fat burned in primitive lamps, illuminating the caves of primitive people, grease was smeared on skids, along which ships were launched. Fats are the main source of our nutrition. But malnutrition, a sedentary lifestyle leads to overweight. Desert animals store fat as a source of energy and water. The thick fat layer of seals and whales helps them swim in the cold waters of the Arctic Ocean.

Fats are widely distributed in nature. Along with carbohydrates and proteins, they are part of all animal and plant organisms and form one of the main parts of our food. Sources of fats are living organisms. Among the animals are cows, pigs, sheep, chickens, seals, whales, geese, fish (sharks, codfish, herring). From the liver of cod and shark, fish oil is obtained - a medicine, from herring - fats used to feed farm animals. Vegetable fats are most often liquid, they are called oils. Fats of plants such as cotton, flax, soybeans, peanuts, sesame, rapeseed, sunflower, mustard, corn, poppy, hemp, coconut, sea buckthorn, dogrose, oil palm and many others are used.

Fats perform various functions: building, energy (1 g of fat gives 9 kcal of energy), protective, storage. Fats provide 50% of the energy required by a person, so a person needs to consume 70-80 g of fat per day. Fats make up 10–20% of a healthy person's body weight. Fats are an essential source of fatty acids. Some fats contain vitamins A, D, E, K, hormones.

Many animals and humans use fat as a heat-insulating shell, for example, in some marine animals, the thickness of the fat layer reaches a meter. In addition, in the body, fats are solvents for flavors and dyes. Many vitamins, such as vitamin A, are soluble only in fats.

Some animals (more often waterfowl) use fats to lubricate their own muscle fibers.

Fats increase the effect of food satiety, as they are digested very slowly and delay the onset of hunger.

The history of the discovery of fats

Back in the 17th century. German scientist, one of the first analytical chemists Otto Tachenius (1652–1699) was the first to suggest that fats contain a “hidden acid”.

In 1741, the French chemist Claude Joseph Geoffroy (1685–1752) discovered that when soap (which was prepared by boiling fat with alkali) decomposes with acid, a mass is greasy to the touch.

The fact that fats and oils contain glycerin was first discovered in 1779 by the famous Swedish chemist Carl Wilhelm Scheele.

For the first time, the chemical composition of fats was determined at the beginning of the last century by the French chemist Michel Eugene Chevreul, the founder of the chemistry of fats, the author of numerous studies of their nature, summarized in a six-volume monograph "Chemical research of bodies of animal origin".

1813E.Chevreul established the structure of fats, thanks to the reaction of hydrolysis of fats in an alkaline medium.He showed that fats are composed of glycerol and fatty acids, and this is not just a mixture of them, but a compound that, by adding water, decomposes into glycerol and acids.

General formula of fats (triglycerides)

Fats- esters of glycerol and higher carboxylic acids.The common name for these compounds is triglycerides.

Fat classification

Animal fats contain mainly glycerides of saturated acids and are solids. Vegetable fats, often referred to as oils, contain glycerides of unsaturated carboxylic acids. These are, for example, liquid sunflower, hemp and linseed oils.

Natural fats contain the following fatty acids

Saturated: stearic(C 17 H 35 COOH) palmitic(C 15 H 31 COOH) Oily (C 3 H 7 COOH)	COMPOSED ANIMALS FAT
Unsaturated: oleic(C 17 H 33 COOH 1double bond) linoleic(C 17 H 31 COOH 2double bonds) linolenic(C 17 H 29 COOH 3double bonds) arachidonic(C 19 H 31 COOH, 4 double bonds, less common)	COMPOSED VEGETABLE FAT

Fats are found in all plants and animals. They are mixtures of full esters of glycerol and do not have a distinct melting point.

• Animal fats (mutton, pork, beef, etc.) are usually solids with a low melting point (fish oil is an exception). Saturated acids predominate in solid fats.
• Vegetable fats - oils (sunflower, soybean, cottonseed, etc.) - liquids (exception - coconut oil, cocoa bean oil). Oils contain mainly residues of unsaturated (unsaturated) acids.
  

Chemical properties of fats

1. Hydrolysis,orsaponification, fatgoing on by the action of water, with the participation of enzymes or acid catalysts(reversible),in this case, an alcohol is formed - glycerol and a mixture of carboxylic acids:

or alkalis (irreversible). Alkaline hydrolysis produces salts of higher fatty acids, calledsoaps. Soaps are obtained by hydrolysis of fats in the presence of alkalis:

Soaps are potassium and sodium salts of higher carboxylic acids.

2. Hydrogenation of fats- the transformation of liquid vegetable oils into solid fats - has great importance for food purposes. The product of hydrogenation of oils is solid fat (artificial lard, lard). Margarine - edible fat, consists of a mixture of hydrogenated oils (sunflower, corn, cottonseed, etc.), animal fats, milk and flavorings (salt, sugar, vitamins, etc.).

This is how margarine is obtained in industry:

Under the conditions of the oil hydrogenation process (high temperature, metal catalyst), some of the acidic residues containing C=C cis bonds are isomerized into more stable trans isomers. The increased content of trans-unsaturated acid residues in margarine (especially in cheap varieties) increases the risk of atherosclerosis, cardiovascular and other diseases.

The use of fats

• 1. food industry
• 1. pharmaceuticals
• 1. Manufacture of soap and cosmetic products
• 1. Lubricant production

Fats are food. The biological role of fats.

Animal fats and vegetable oils, along with proteins and carbohydrates, are one of the main components of normal human nutrition. They are the main source of energy: 1 g of fat when completely oxidized (it takes place in cells with the participation of oxygen) provides 9.5 kcal (about 40 kJ) of energy, which is almost twice as much as can be obtained from proteins or carbohydrates. In addition, fat reserves in the body practically do not contain water, while protein and carbohydrate molecules are always surrounded by water molecules. As a result, one gram of fat provides almost 6 times more energy than one gram of animal starch - glycogen. Thus, fat should rightly be considered a high-calorie "fuel". It is mainly used to maintain normal temperature. human body, as well as for the work of various muscles, so even when a person does nothing (for example, sleeps), every hour he needs about 350 kJ of energy to cover energy costs, about the same power a 100-watt electric light bulb has.

To provide the body with energy in adverse conditions, fat reserves are created in it, which are deposited in the subcutaneous tissue, in the fatty fold of the peritoneum - the so-called omentum. Subcutaneous fat protects the body from hypothermia (especially this function of fat is important for marine animals). For thousands of years, people have been doing hard physical work, which required a lot of energy and, accordingly, enhanced nutrition. Only 50 g of fat is enough to cover the minimum daily human need for energy. However, with moderate physical activity, an adult should receive slightly more fat from food, but their amount should not exceed 100 g (this gives a third of the calorie content of a diet of about 3000 kcal). It should be noted that half of these 100 g is found in food in the form of so-called hidden fat. Fats are found in almost all foods: in small quantities they are even in potatoes (there are 0.4%), in bread (1–2%), and in oatmeal (6%). Milk usually contains 2-3% fat (but there are also special varieties of skimmed milk). Quite a lot of hidden fat in lean meat - from 2 to 33%. Hidden fat is present in the product in the form of individual tiny particles. Fats in almost pure form are lard and vegetable oil; in butter about 80% fat, in ghee - 98%. Of course, all the above recommendations for fat consumption are averages, they depend on gender and age, physical activity and climatic conditions. With excessive consumption of fats, a person quickly gains weight, but we should not forget that fats in the body can also be synthesized from other products. It is not so easy to “work off” extra calories through physical activity. For example, jogging 7 km, a person spends about the same amount of energy as he receives by eating just one hundred-gram bar of chocolate (35% fat, 55% carbohydrates). Physiologists have found that during physical activity, which is 10 times higher than usual, a person who received a fat diet was completely exhausted after 1.5 hours. With a carbohydrate diet, a person withstood the same load for 4 hours. This seemingly paradoxical result is explained by the peculiarities of biochemical processes. Despite the high "energy intensity" of fats, obtaining energy from them in the body is a slow process. This is due to the low reactivity of fats, especially their hydrocarbon chains. Carbohydrates, although they provide less energy than fats, "allocate" it much faster. Therefore, before physical activity, it is preferable to eat sweet, rather than fatty. An excess of fats in food, especially animal fats, also increases the risk of developing diseases such as atherosclerosis, heart failure, etc. Animal fats contain a lot of cholesterol (but we should not forget that two-thirds of cholesterol is synthesized in the body from non-fat foods - carbohydrates and proteins).

It is known that a significant proportion of fat consumed should be vegetable oils, which contain compounds that are very important for the body - polyunsaturated fatty acids with several double bonds. These acids are called "essential". Like vitamins, they must be supplied to the body in finished form. Of these, arachidonic acid has the highest activity (it is synthesized in the body from linoleic acid), the least activity is linolenic acid (10 times lower than linoleic acid). According to various estimates, the daily human need for linoleic acid ranges from 4 to 10 g. Most of all linoleic acid (up to 84%) is in safflower oil, squeezed from safflower seeds, an annual plant with bright orange flowers. A lot of this acid is also found in sunflower and nut oils.

According to nutritionists, a balanced diet should contain 10% polyunsaturated acids, 60% monounsaturated (mainly oleic acid) and 30% saturated. It is this ratio that is ensured if a person receives a third of the fats in the form of liquid vegetable oils - in the amount of 30–35 g per day. These oils are also found in margarine, which contains 15 to 22% saturated fatty acids, 27 to 49% unsaturated fatty acids, and 30 to 54% polyunsaturated fatty acids. By comparison, butter contains 45–50% saturated fatty acids, 22–27% unsaturated fatty acids, and less than 1% polyunsaturated fatty acids. In this respect, high-quality margarine is healthier than butter.

Need to remember

Saturated fatty acids negatively affect fat metabolism, liver function and contribute to the development of atherosclerosis. Unsaturated (especially linoleic and arachidonic acids) regulate fat metabolism and are involved in the removal of cholesterol from the body. The higher the content of unsaturated fatty acids, the lower the melting point of the fat. The calorie content of solid animal and liquid vegetable fats is approximately the same, but the physiological value of vegetable fats is much higher. Milk fat has more valuable qualities. It contains one third of unsaturated fatty acids and, remaining in the form of an emulsion, is easily absorbed by the body. Despite these positive traits, you can not use only milk fat, since no fat contains an ideal composition of fatty acids. It is best to consume fats of both animal and vegetable origin. Their ratio should be 1:2.3 (70% animal and 30% vegetable) for young people and middle-aged people. The diet of older people should be dominated by vegetable fats.

Fats are not only involved in metabolic processes, but also deposited in reserve (mainly in the abdominal wall and around the kidneys). Fat reserves provide metabolic processes, keeping proteins for life. This fat provides energy during physical activity, if there is little fat in the diet, as well as in severe illness, when due to reduced appetite, it is not enough supplied with food.

Abundant consumption of fat with food is harmful to health: it is stored in large quantities in reserve, which increases body weight, sometimes leading to disfigurement of the figure. Its concentration in the blood increases, which, as a risk factor, contributes to the development of atherosclerosis, coronary heart disease, hypertension, etc.

COR:

hydrolysis of fats. Hydrogenation of liquid fats

Fat classification

The structure of fats

Natural fats (triacylglycerols) are triesters of glycerol and fatty acids. The common name for these compounds is triglycerides. Known not only glycerides of the same acids (simple glycerides), but also predominantly different acids (mixed glycerides). For example:

The names of esters are derived from the name of the hydrocarbon radical and the name of the acid, in which the suffix -at is used instead of the ending -ova, for example:

Esters are characterized by the following types of isomerism:

1. The isomerism of the carbon chain begins at the acid residue with butanoic acid, at the alcohol residue - with propyl alcohol, for example, ethyl isobutyrate, propyl acetate and isopropyl acetate are isomers of ethyl butyrate.

2. Isomerism of the position of the ester group -CO-O-. This type of isomerism begins with esters whose molecules contain at least 4 carbon atoms, such as ethyl acetate and methyl propionate.

3. Interclass isomerism, for example propanoic acid is isomeric to methyl acetate.

For esters containing unsaturated acid or unsaturated alcohol, two more types of isomerism are possible: isomerism of the position of the multiple bond and cis-, trans-isomerism.

Fatty acid - belong to the group of carboxylic acids.

Carboxylic acids are those organic acids that contain at least one carboxyl group. The classification of carboxylic acids is based on the number of carboxyl groups. Fatty acids are classified as monocarboxylic acids. From the point of view of the chemical structure, all carboxylic acids are divided into two groups:

1) saturated or saturated carboxylic acids, in the radical of which there are only single bonds between carbon atoms.

2) unsaturated or unsaturated, in the radical of which there are double bonds. The number of double bonds is a classification feature, which is denoted by the suffix -en.

Biologically important are short radical saturated acids from C 1 to C 8 . Such short radical acids are important intermediate products of metabolic pathways in the cell.

After From 8 only fatty acids with an even number of carbon atoms in the radical are of biological importance, because all of them are synthesized on the basis of acetic acid.

Limit fatty acids are found in the body up to From 24, with an increase in the length of the radical, the phase state of the acid changes.

Briefly, radical fatty acids are liquids. The longer the radical, the harder the acid.

Among unsaturated fatty acids, tetraenoic, pentoenoic and hexaenoic fatty acids are of biological importance.

Pentoene And hexaenoic found in fish oils.

Tetroenic in peanut butter.

The degree of saturation of a fatty acid determines its phase state.

Saturated fatty acids are solid, unsaturated fatty acids are liquid. Fatty acid molecules combine the two properties of hydrophobicity and hydrophilicity, so they are said to have amphoteric properties. If the fatty acid radical is short enough, then it is soluble in water; if the radical is long, then it is poorly soluble in water.

Simple lipids are esters of fatty acids and alcohols. They are formed by an esterification reaction.

All simple lipids are divided into three groups:

1) wax; 2) fats; 3) Ceramide

These are esters of a fatty acid with a monohydric alcohol. Waxes are characteristic of the plant world and often cover the vegetative organs of plants living in arid conditions (stone ivy, cacti, lingonberries). They prevent excessive evaporation of water, reflect the sun's rays, which prevents overheating of plants and excessive ultraviolet radiation. Waxes are less common in animals; in insects, a wax coating covers the cuticle, preventing water from evaporating. In humans, there are also waxes that are secreted to the surface of the epidermis and derivatives of the epidermis, such as hair and nails.