Fatty acid. All about unsaturated fatty acids

Over 200 fatty acids have been found in nature, which are part of the lipids of microorganisms, plants and animals.

Fatty acids are aliphatic carboxylic acids (Figure 3). They can be found in the body either in a free state or act as building blocks for most classes of lipids.

All fatty acids that make up fats are divided into two groups: saturated and unsaturated. Unsaturated fatty acids that have two or more double bonds are called polyunsaturated. Natural fatty acids are very diverse, but have a number of common features. These are monocarboxylic acids containing linear hydrocarbon chains. Almost all of them contain an even number of carbon atoms (from 14 to 22, most often found with 16 or 18 carbon atoms). Much less common are fatty acids with shorter chains or with an odd number of carbon atoms. The content of unsaturated fatty acids in lipids is usually higher than saturated ones. Double bonds are typically found between carbons 9 and 10, are almost always separated by a methylene group, and are in the cis configuration.

Trans-isomers of fatty acids are also found. They are found in dairy products, meat and cattle fat, and in hydrogenated vegetable fats. Trans isomers have a negative impact on human health: by increasing the level of low-density lipids in the blood, which are dangerous for vascular walls, they increase the risk of cardiovascular diseases. There are no restrictions on the level of trans isomers in EU countries yet (with the exception of Denmark). Denmark is the first country to introduce a standard for the content of trans isomers - no more than 2%.

Figure 4 – Basic structure and nomenclature of fatty acids

Higher fatty acids are practically insoluble in water, but their sodium or potassium salts, called soaps, form micelles in water that are stabilized by hydrophobic interactions. Soaps have the properties of surfactants.

Fatty acids differ:

– the length of their hydrocarbon tail, the degree of their unsaturation and the position of double bonds in the fatty acid chains;

– physical and chemical properties. Typically, saturated fatty acids at a temperature of 22 0 C have a solid consistency, while unsaturated fatty acids are oils.

Unsaturated fatty acids have a lower melting point. Polyunsaturated fatty acids oxidize faster in open air than saturated fatty acids. Oxygen reacts with double bonds to form peroxides and free radicals;

– structural organization. In saturated fatty acids, the hydrocarbon tail can, in principle, take on an infinite number of configurations due to complete freedom of rotation around the single bond; however, the most likely is the elongated form, since it is energetically the most favorable. In unsaturated acids, a different picture is observed: the impossibility of rotation around the double bond (or bonds) causes a rigid bend of the hydrocarbon chain. In natural fatty acids, the double bond, being in the cis configuration, gives the chain a bend at an angle of approximately 30 0 . In fatty acids with multiple double bonds, the cis configuration gives the carbon chain a bent and shortened appearance. This bend prevents the formation of the orderly structural organization between adjacent molecules characteristic of saturated fatty acids, and consequently van der Waals interactions between the hydrocarbon tails of unsaturated acids are weakened. As a result, cis-unsaturated fatty acids have a lower melting point than saturated fatty acids. The cis form is less stable than the trans form. Table 1 lists the fatty acids most commonly found in natural lipids.

Table 1 - Main carboxylic acids included in lipids

(with only single bonds between carbon atoms), monounsaturated (with one double bond between carbon atoms) and polyunsaturated (with two or more double bonds, usually located through the CH 2 group). They differ in the number of carbon atoms in the chain and, in the case of unsaturated acids, in position, configuration (usually cis-) and number of double bonds. Fatty acids can be roughly divided into lower (up to seven carbon atoms), medium (eight to twelve carbon atoms) and higher (more than twelve carbon atoms). Based on the historical name, these substances must be components of fats. Today this is not the case; The term “fatty acids” refers to a broader group of substances.

Carboxylic acids starting with butyric acid (C4) are considered fatty acids, while fatty acids obtained directly from animal fats generally have eight or more carbon atoms (caprylic acid). The number of carbon atoms in natural fatty acids is mostly even, which is due to their biosynthesis with the participation of acetyl coenzyme A.

A large group of fatty acids (over 400 different structures, although only 10-12 are common) are found in vegetable seed oils. There is a high percentage of rare fatty acids in the seeds of certain plant families.

R-COOH + CoA-SH + ATP → R-CO-S-CoA + 2P i + H + + AMP

Synthesis

Circulation

Digestion and absorption

Short- and medium-chain fatty acids are absorbed directly into the blood through the capillaries of the intestinal tract and pass through the portal vein, like other nutrients. The longer chain ones are too large to pass directly through the small capillaries of the intestine. Instead, they are absorbed by the fatty walls of the intestinal villi and re-synthesized into triglycerides. Triglycerides are coated with cholesterol and proteins to form chylomicrons. Inside the villi, the chylomicron enters the lymphatic vessels, the so-called lacteal capillary, where it is absorbed by the large lymphatic vessels. It is transported through the lymphatic system all the way to a place close to the heart where the blood arteries and veins are largest. The thoracic canal releases chylomicrons into the bloodstream through the subclavian vein. In this way, triglycerides are transported to places where they are needed.

Types of existence in the body

Fatty acids exist in different forms at different stages of the blood circulation. They are absorbed in the intestine to form chylomicrons, but at the same time they exist as very low-density lipoproteins or low-density lipoproteins after conversion in the liver. When released from adipocytes, fatty acids enter the blood freely.

Acidity

Acids with a short hydrocarbon tail, such as formic and acetic acids, are completely miscible with water and dissociate to form fairly acidic solutions (pK a 3.77 and 4.76, respectively). Fatty acids with a longer tail differ slightly in acidity. For example, nonanoic acid has a pK a of 4.96. However, as the tail length increases, the solubility of fatty acids in water decreases very quickly, resulting in these acids making little difference to the solution. The value of pK a values ​​for these acids becomes significant only in the reactions in which these acids are capable of entering. Acids that are insoluble in water can be dissolved in warm ethanol and titrated with sodium hydroxide solution, using phenolphthalein as an indicator, to a pale pink color. This analysis allows you to determine the fatty acid content of a portion of triglycerides after hydrolysis.

Fatty acid reactions

Fatty acids react in the same way as other carboxylic acids, which involves esterification and acid reactions. Reduction of fatty acids results in fatty alcohols. Unsaturated fatty acids can also undergo addition reactions; most typically hydrogenation, which is used to convert vegetable fats into margarine. As a result of partial hydrogenation of unsaturated fatty acids, cis isomers characteristic of natural fats can transform into trans form. In the Warrentrapp reaction, unsaturated fats can be broken down in molten alkali. This reaction is important for determining the structure of unsaturated fatty acids.

Auto-oxidation and rancidity

Fatty acids undergo auto-oxidation and rancidity at room temperature. In doing so, they decompose into hydrocarbons, ketones, aldehydes and small amounts of epoxides and alcohols. Heavy metals, contained in small quantities in fats and oils, accelerate autoxidation. To avoid this, fats and oils are often treated with chelating agents such as citric acid.

Application

Sodium and potassium salts of higher fatty acids are effective surfactants and are used as soaps. In the food industry, fatty acids are registered as food additives E570, as a foam stabilizer, glazing agent and defoamer.

Branched fatty acids

Branched carboxylic acids of lipids are usually not classified as fatty acids themselves, but are considered as their methylated derivatives. Methylated at the penultimate carbon atom ( iso-fatty acids) and at the third from the end of the chain ( anteiso-fatty acids) are included as minor components in the composition of lipids of bacteria and animals.

Branched carboxylic acids are also part of the essential oils of some plants: for example, valerian essential oil contains isovaleric acid:

Essential fatty acids

Saturated fatty acids

General formula: C n H 2n+1 COOH or CH 3 -(CH 2) n -COOH

Monounsaturated fatty acids

General formula: CH 3 -(CH 2) m -CH=CH-(CH 2) n -COOH (m = ω -2; n = Δ -2)

Polyunsaturated fatty acids

General formula: CH 3 -(CH 2) m -(CH=CH-(CH 2) x (CH 2)n-COOH

Notes

see also

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See what “Fatty acids” are in other dictionaries:

Monobasic carboxylic acids aliphatic. row. Basic structural component plural lipids (neutral fats, phosphoglycerides, waxes, etc.). Free fatty acids are present in organisms in trace amounts. Predominant in living nature. there are higher women... ... Biological encyclopedic dictionary

fatty acid- High-molecular carboxylic acids that are part of vegetable oils, animal fats and related substances. Note For hydrogenation, fatty acids isolated from vegetable oils, animal fats and fat wastes are used.… … Technical Translator's Guide

FATTY ACIDS, organic compounds, constituent components of FAT (hence the name). In composition, they are carboxylic acids containing one carboxyl group (COOH). Examples of saturated fatty acids (in the hydrocarbon chain... ... Scientific and technical encyclopedic dictionary

Fatty acids are part of all saponified lipids. In humans, fatty acids are characterized by the following features:

• an even number of carbon atoms in the chain,
• no chain branches,
• the presence of double bonds only in the cis conformation.

In turn, fatty acids are heterogeneous in structure and differ in chain length and number of double bonds.

Saturated fatty acids include palmitic (C16), stearic (C18) and arachidic (C20). TO monounsaturated– palmitooleic (C16:1, Δ9), oleic (C18:1, Δ9). These fatty acids are found in most dietary fats and human fat.

Polyunsaturated fatty acids contain 2 or more double bonds separated by a methylene group. In addition to the differences in quantity double bonds, acids differ position double bonds relative to the beginning of the chain (denoted by the Greek letter Δ " delta") or the last carbon atom of the chain (denoted by ω " omega").

According to the position of the double bond relative to last carbon atom, polyunsaturated fatty acids are divided into ω9, ω6 and ω3 fatty acids.

1. ω6-fatty acids. These acids are collectively called vitamin F, and are found in vegetable oils.

• linoleic (C18:2, Δ9.12),
• γ-linolenic (C18:3, Δ6,9,12),
• arachidonic (eicosotetraenoic, C20:4, Δ5,8,11,14).

2. ω3-fatty acids:

• α-linolenic (C18:3, Δ9,12,15),
• timnodonic (eicosapentaenoic, C20:5, Δ5,8,11,14,17),
• clupanodone (docosopentaenoic, C22:5, Δ7,10,13,16,19),
• cervonic acid (docosohexaenoic acid, C22:6, Δ4,7,10,13,16,19).

Food sources

Since fatty acids determine the properties of the molecules they are part of, they are found in completely different products. Source of saturated and monounsaturated fatty acids are solid fats - butter, cheese and other dairy products, lard and beef fat.

Polyunsaturated ω6-fatty acids are represented in large numbers in vegetable oils(except olive and palm) – sunflower, hemp, linseed oil. Arachidonic acid is also found in small amounts in pork fat and dairy products.

The most significant source ω3-fatty acids serves fish oil cold seas - primarily cod oil. An exception is α-linolenic acid, found in hemp, flaxseed, and corn oils.

The role of fatty acids

1. It is with fatty acids that the most famous function of lipids is associated - energy. Thanks to oxidation saturated fatty acids, body tissues receive more than half of all energy (β-oxidation), only red blood cells and nerve cells do not use them in this capacity. As an energy substrate, they are usually used rich And monounsaturated fatty acid.

2. Fatty acids are part of phospholipids and triacylglycerols. Availability polyunsaturated fatty acids determine biological activity phospholipids, properties of biological membranes, interaction of phospholipids with membrane proteins and their transport and receptor activity.

3. Long-chain (C22, C24) polyunsaturated fatty acids have been found to participate in memory mechanisms and behavioral reactions.

4. Another, and very important function of unsaturated fatty acids, namely those that contain 20 carbon atoms and form a group eicosanoic acids(eicosotriene (C20:3), arachidonic (C20:4), timnodonic (C20:5)), is that they are a substrate for the synthesis of eicosanoids () - biologically active substances that change the amount of cAMP and cGMP in the cell, modulating metabolism and activity of both the cell itself and surrounding cells. Otherwise, these substances are called local or tissue hormones.

The attention of researchers to ω3-acids was attracted by the phenomenon of the Eskimos (indigenous inhabitants of Greenland) and the indigenous peoples of the Russian Arctic. Despite their high intake of animal protein and fat and very little plant foods, they had a condition called antiatherosclerosis. This condition is characterized by a number of positive features:

• absence of incidence of atherosclerosis, coronary heart disease and myocardial infarction, stroke, hypertension;
• increased content of high-density lipoproteins (HDL) in the blood plasma, decreased concentrations of total cholesterol and low-density lipoproteins (LDL);
• reduced platelet aggregation, low blood viscosity;
• different fatty acid composition of cell membranes compared to Europeans - C20:5 was 4 times more, C22:6 16 times!

1. B experiments to study the pathogenesis of type 1 diabetes mellitus in rats, it was found that preliminary the use of ω-3 fatty acids reduced the death of pancreatic β-cells in experimental rats when using the toxic compound alloxan ( alloxan diabetes).

2. Indications for use of ω-3 fatty acids:

• prevention and treatment of thrombosis and atherosclerosis,
• insulin-dependent and non-insulin-dependent diabetes mellitus, diabetic retinopathy,
• dyslipoproteinemia, hypercholesterolemia, hypertriacylglycerolemia, biliary dyskinesia,
• myocardial arrhythmias (improved conductivity and rhythm),
• peripheral circulatory disorder.

And these two videos will tell you how to prepare salmon rolls.

Place in the freezer

Unsaturated fatty acids are acids containing double bonds in the carbon skeleton.

Depending on the degree of unsaturation (the number of double bonds), they are divided into:

1. Monounsaturated (monoethenoid, monoenoic) acids - contain one double bond.

2. Polyunsaturated (polyethenoid, polyenoic) acids - contain more than two double bonds. Some authors classify polyenoic acids as unsaturated fatty acids containing three or more multiple (double) bonds.

Unsaturated fatty acids exhibit geometric isomerism due to differences in the orientation of atoms or groups relative to the double bond. If the acyl chains are located on one side of the double bond, cis- a configuration characteristic, for example, of oleic acid; if they are located on opposite sides of the double bond, then the molecule is in trance- configurations.

Table 6.3

Unsaturated fatty acids

Continuation of the table. 6.3

Unsaturated fatty acids include hydroxy acids, for example, ricinoleic acid, which has a hydroxyl group at the C 12 atom:

C 21 H 41 COOH

CH 3 – (CH 2) 7 – CH = CH – (CH 2) 11 COOH

Cyclic unsaturated fatty acids

Molecules of cyclic unsaturated acids contain slightly reactive carbon cycles. Typical examples are hydrocarpic and chaulmougric acids.

Hydnocarpic acid CH=CH

> CH–(CH 2) 10 –COOH

CH 2 –CH 2

Chaulmugric acid CH = CH

> CH – (CH 2) 12 – COOH

CH 2 –CH 2

These acids are found in tropical plant oils used to treat leprosy and tuberculosis.

Irreplaceable ( essential)fatty acid

In 1928, Evans and Burr discovered that rats fed a low-fat diet, but containing vitamins A and D, experienced slow growth and decreased fertility, scaly dermatitis, tail necrosis, and damage to the urinary system. In their work, they showed that this syndrome can be treated by adding essential fatty acids to food.

Essential fatty acids are acids that are not synthesized by the human body, but enter it with food. Essential acids are:

Linoleic C17H31COOH (two double bonds), C218;

Linolenic C17H29COOH (three double bonds), C318;

Arachidonic C 19 H 31 COOH (four double bonds), C 4 20.

Linoleic and linolenic acids are not synthesized in the human body, arachidonic acid is synthesized from linoleic acid with the help of vitamin B6.

These acids are vitamin F (from the English. fat– fat), are part of vegetable oils.

People whose diet lacks essential fatty acids develop scaly dermatitis, a disorder of lipid transport. To avoid these disorders, ensure that essential fatty acids account for up to 2% of total calories. Essential fatty acids are used by the body as precursors for the biosynthesis of prostaglandins and leukotrienes, participate in the construction of cell membranes, regulation of metabolism in cells, blood pressure, platelet aggregation, remove excess cholesterol from the body, thus reducing the likelihood of developing atherosclerosis, increase the elasticity of the walls of blood vessels . Arachidonic acid has the greatest activity, linoleic acid has intermediate activity, the activity of linolenic acid is 8-10 times lower than linoleic acid.

Linoleic and arachidonic acids are w-6-acids,
a-linolenic – w-3-acid, g-linolenic – w-6-acid. Linoleic, arachidonic and g-linolenic acids are members of the omega-6 family.

Linoleic acid is part of the g-linolenic composition of many vegetable oils; it is found in wheat, peanuts, cotton seeds, and soybeans. Arachidonic acid, found together with linoleic acid, especially in peanut butter, is an important element of animal phospholipids. a-Linolenic acid is also found along with linoleic acid, especially in flaxseed oil,
g-linolenic – characteristic of rose oil.

The daily requirement for linoleic acid is 6–10 g, its total content in dietary fats should be at least 4% of the total calorie content. For a healthy body, the ratio of fatty acids should be balanced: 10–20% polyunsaturated, 50–60% monounsaturated and 30% saturated. For elderly people and patients with cardiovascular diseases, the linoleic acid content should be 40% of the total fatty acid content. The ratio of polyunsaturated and saturated acids is 2:1, the ratio of linoleic and linolenic acids is 10:1.

To assess the ability of fatty acids to provide the synthesis of structural components of cell membranes, the coefficient of efficiency of metabolization of essential fatty acids (ECM) is used, which shows the ratio of the amount of arachidonic acid (the main representative of unsaturated fatty acids in membrane lipids) to the sum of polyunsaturated fatty acids with 20 and 22 carbon atoms:

Simple lipids(multi-component)

Simple lipids are esters of alcohols and higher fatty acids. These include triacylglycerides (fats), waxes, sterols and sterides.

Waxes

Waxes are esters of higher monobasic fatty acids () and primary monohydric high molecular weight alcohols (). Chemically inactive, resistant to bacterial action. Enzymes do not break them down.

General wax formula:

R 1 –O–CO–R 2 ,

where R 1 O - is the remainder of a high molecular weight monohydric primary alcohol; R 2 CO is a fatty acid residue, predominantly with an even number of C atoms.

Waxes are widely distributed in nature. Waxes form a protective coating on leaves, stems, and fruits, protecting them from wetting with water, drying out, and the action of microorganisms. Waxes form a protective lubricant on the skin, fur, feathers, and are found in the exoskeleton of insects. They are an important component of the waxy coating of grape berries - pruin. In the shells of soybean seeds, the wax content is 0.01% by weight of the shell, in the shells of sunflower seeds - 0.2%, in the shells of rice - 0.05%.

A typical example of wax is beeswax, containing alcohols with 24–30 C atoms (myricyl alcohol C 30 H 61 OH), acids CH 3 (CH 2) n COOH, where n= 22–32, and palmitic acid (C 30 H 61 – O–СO–C 15 H 31).

Spermaceti

An example of an animal wax is spermaceti wax. Raw (technical) spermaceti is obtained from the head spermaceti cushion of sperm whales (or other toothed whales). Raw spermaceti consists of white scaly crystals of spermaceti and spermaceti oil (spermole).

Pure spermaceti is an ester of cetyl alcohol (C 16 H 33 OH) and palmitic acid (C 15 H 31 CO 2 H). The formula of pure spermaceti is C 15 H 31 CO 2 C 16 H 33.

Spermaceti is used in medicine as a component of ointments that have a healing effect.

Spermol is a liquid wax, a light yellow oily liquid, a mixture of liquid esters containing oleic acid C 17 H 33 COOH and oleic alcohol C 18 H 35. Spermole formula C 17 H 33 CO–O–C 18 H 35 . The melting point of liquid spermaceti is 42...47 0 C, spermaceti oil is 5...6 0 C. Spermaceti oil contains more unsaturated fatty acids (iodine number 50–92) than spermaceti (iodine number 3–10).

Sterols and steroids

Sterols(sterols) are high molecular weight polycyclic alcohols, an unsaponifiable fraction of lipids. Representatives are: cholesterol or cholesterol, oxycholesterol or oxycholesterol, dehydrocholesterol or dehydrocholesterol, 7-dehydrocholesterol or 7-dehydrocholesterol, ergosterol or ergosterol.

At the heart of the structure sterols lies a ring containing fully hydrogenated phenanthrene (three cyclohexane rings) and cyclopentane.

Steroids– sterol esters – are the saponified fraction.

Steroids– these are biologically active substances, the basis of the structure of which are sterols.

In the 17th century, cholesterol was first isolated from gallstones (from the Greek. сhole– bile).

CH 3 CH - CH 2 - CH 2 – CH 2 - CH

It is found in nervous tissue, brain, liver, and is a precursor of biologically active steroid compounds (for example: bile acids, steroid hormones, vitamins D) and a bioisolator that protects the structures of nerve cells from the electrical charge of nerve impulses. Cholesterol in the body is found in free (90%) form and in the form of esters. It has endo- and exogenous nature. Endogenous cholesterol is synthesized in the human body (70–80% of cholesterol is synthesized in the liver and other tissues). Exogenous cholesterol is cholesterol that comes from food.

Excess cholesterol causes atherosclerotic plaques to form on the walls of the arteries (atherosclerosis). Normal level
200 mg of cholesterol per 100 ml of blood. When cholesterol levels in the blood increase, there is a risk of atherosclerosis.

Daily cholesterol intake from food should not exceed 0.5 g.

More cholesterol is found in eggs, butter, and offal. In fish, high cholesterol content was found in caviar (290–2200 mg/100 g) and milk (250–320 mg/100 g).

Fats(TAG, triacylglycerides)

Fats are esters of glycerol and higher fatty acids and are the saponified fraction.

General TAG formula:

CH 2 – O – CO – R 1

CH – O – CO – R 2

CH 2 – O – CO – R 3,

where R1, R2, R3 are residues of saturated and unsaturated fatty acids.

Depending on the composition of fatty acids, TAGs can be simple (have the same fatty acid residues) or mixed (have different fatty acid residues). Natural fats and oils contain mainly mixed TAGs.

Fats are divided into solid and liquid. Solid fats contain saturated carboxylic acids, these include animal fats. Liquid fats contain unsaturated acids, these include vegetable oils and fish oil.

Fish oils are characterized by polyene fatty acids, which have a linear chain and contain 4–6 double bonds.

The high biological value of fish oil is determined by the fact that fish oil contains:

Biologically active polyene fatty acids (docosahexaenoic acid, eicosapentaenoic acid). Polyenoic acids reduce the risk of thrombosis and atherosclerosis;

Vitamin A;

Vitamin D;

Vitamin E;

Microelement selenium.

Fish fats are divided into low-vitamin and high-vitamin. In low-vitamin fish oils, the vitamin A content is less than 2000 IU per 1 g, in high-vitamin fish oils it exceeds 2000 IU per 1 g. In addition, vitamin A concentrates are produced industrially - fats in which the vitamin A content is > 10 4 IU
in 1 year

Fat quality indicators

To assess the quality of fats, the following physicochemical constants are used.

1. Acid number.

A characteristic property of fats is their ability to hydrolyze. The products of hydrolysis are free fatty acids, glycerol, monoacylglycerides and diacylglycerides.

Enzymatic hydrolysis of fats occurs with the participation of lipase. This is a reversible process. To assess the degree of hydrolysis and the amount of free fatty acids, the acid number is determined.

Acid value is the number of milligrams of KOH used to neutralize all free fatty acids contained in 1 g of fat. The higher the acid number, the higher the content of free fatty acids, the more intense the hydrolysis process. The acid number increases during fat storage, i.e., it is an indicator of hydrolytic spoilage.

The acid number of medical fat should be no more than 2.2, fortified fat intended for veterinary purposes - no more than 3, edible fat - 2.5.

2. Peroxide number

The peroxide number characterizes the process of oxidative deterioration of fats, which results in the formation of peroxides.

The peroxide number is determined by the number of grams of iodine isolated from potassium iodide in the presence of glacial acetic acid, releasing I 2 from it; the formation of free iodine is fixed using starch paste:

ROOH + 2KI + H 2 O = 2KOH + I 2 + ROH.

To increase the sensitivity of the study, the determination of the peroxide number is carried out in an acidic environment, acting on peroxides not with potassium iodide, but with hydroiodic acid, formed from potassium iodide when exposed to acid:

KI + CH 3 COOH = HI + CH 3 COOK

ROOH + 2HI = I 2 + H 2 O + ROH

The released iodine is immediately titrated with sodium thiosulfate solution.

3. Hydrogen number

The hydrogen number, like the iodine number, is an indicator of the degree of unsaturation of fatty acids.

Hydrogen number is the number of milligrams of hydrogen required to saturate 100 g of the fat under study.

4. Saponification number

The saponification number is the number of milligrams of KOH required to neutralize all free and bound acids contained in 1 g of fat:

CH 2 OCOR 1 CH 2 - OH

CHOCOR 2 + 3KOH CH - OH + R 1 COOK +

CH 2 OCOR 3 CH 2 - OH

bound fatty acids

R 2 COOK + R 3 COOK

RCOOH + KOH –––® RCOOK + H 2 O

free

fatty acid

The saponification number characterizes the nature of the fat: the lower the molar mass of TAG, the greater the saponification number. The saponification number characterizes the average molecular weight of glycerides and depends on the molecular weight of fatty acids.

The saponification number and acid number characterize the degree of hydrolytic spoilage of fat. The saponification number is influenced by the content of unsaponifiable lipids.

5. Aldehyde number

The aldehyde number characterizes the oxidative deterioration of fats and the content of aldehydes in fat. The aldehyde number is determined by a photocolorimetric method based on the interaction of carbonyl compounds with benzidine; Determination of optical density is carried out at a wavelength of 360 nm. Cinnamaldehyde (b-phenylacrolein C 6 H 5 CH=CHCHO) is used to construct a calibration curve. The aldehyde number is expressed in milligrams of cinnamaldehyde per 100 g of fat. Aldehyde number is an indicator of the quality of dried fish, as well as the second stage of oxidative spoilage of fats.

6. Essential number

The ester number is the number of milligrams of KOH required to neutralize the ester bonds of fatty acids (bound fatty acids) released during saponification in 1 g of fat. The essential number is determined by the difference between the saponification number and the acid number. The essential number characterizes the nature of the fat.