Fats – the usual name for a group of lipids, glycerol esters and fatty acids, mainly triacylglycerols. The acid residues found in fat molecules usually contain from 12 to 18 carbon atoms.

Most fats have no odor, are insoluble in water and polar solvents, and are well soluble in non-polar solvents. All fats are lighter than water, the reaction of fats is neutral. Their physical state depends on what acid residues make up the molecule. Solid fats contain saturated acid residues with long carbon chains, while liquid fats contain unsaturated acid residues (residues with double bonds) or acid residues with short carbon chains. The unsaturated acids found in natural fats are cis isomers. Most fats are mixed esters, i.e. those that contain various acid residues in the molecule.

Natural fats are always mixtures of different glycerol esters. At room temperature, animal fats are usually solids (the exception is e.g. fish oil), vegetable fats are liquids (exceptions are e.g. cocoa butter and coconut oil).

Usage
Vegetable fats such as olive oil, rapeseed, sunflower, peanut, linseed, cocoa butter are purified, hardened or dehydrated, and then used in the food, soap, textile and medical industries.
Edible fats have a wide culinary use. In the kitchen, they occur in the form of highly concentrated products, such as butter, lard, oil, tallow (kitchen) and olive oil. They are used for spreading bread and baking and frying dishes.

The role of fat in the diet
Fats fulfill a number of important roles in the human diet. First of all, they provide a significant amount of energy. From one gram of fat, the human body obtains about 37.7 kJ of energy, i.e. approximately twice as much as from protein and saccharides. Fats are also the main source of essential unsaturated fatty acids (EFAs) and fat-soluble vitamins (A, D, E, K). Some fatty acids are also involved in the synthesis of some tissue hormones, including Prostaglandins. Fats in moderate amounts are an essential nutrient for humans. They are the main source of glycerol and fatty acids from which the body synthesizes other lipids. Eating excess food including fat causes overweight, while eating excess saturated fat promotes cardiovascular disease. The demand for fat is lower in the elderly and those who lead a low physical activity.
Fats should provide no more than 30% of energy contained in food and contain an appropriate amount of unsaturated fatty acids. The amounts of fat consumed by people of different ages should be roughly as follows:

women
10-12 years – 62 to 74 g
16-18 years – 72 to 95 g
26-61 years – 57 to 97 g

men
10-12 years – 65 to 81 g
16-18 years old – 82 to 117 g
26-61 years – 73 to 120 g

In dietetics, fats are divided into “visible” and “invisible”. Invisible is understood as fats contained in food products not directly associated with fat in the colloquial meaning of the word, e.g. in sweets, baked goods, etc.
Fats in the body of animals and humans are stored in adipose tissue, which acts as an energy storage, as well as thermal insulation and mechanical protection.

Harmful action
High consumption of omega 6 polyunsaturated fats (present especially in vegetable oil from soybeans, corn, sunflower and other seed oils, in margarine), e.g. linoleic acid, with a deficiency of omega 3 polyunsaturated fats (in fish oil, but also in linseed oil; oil rapeseed contains almost as much unwanted omega 9 olein fat as oil), promotes the development of breast cancer. In 2001, it was found that the presence of omega-9 monounsaturated fats and some omega-6 polyunsaturated fats in erythrocytes may promote the development of breast cancer in postmenopausal women, and that the presence of omega-3 polyunsaturated fats prevents. The composition of fats in erythrocytes can result from both diet and endogenous synthesis and metabolism of acid residues.
Omega 6 polyunsaturated fats with a deficiency of omega 3 polyunsaturated fats stimulate the growth of prostate tumors, accelerate histopathological progression and reduce the survival rate of patients with prostate cancer, whereas omega 3 polyunsaturated fats (in rapeseed oil) have the opposite positive effect.

Physical properties of fats
• pure fats are colorless and odorless substances (the smell, color and taste of natural fats come from their admixtures)
• They dissolve very well in hydrocarbons, e.g. gasoline, kerosene
• insoluble in water
• shaken with water they form an emulsion in which tiny fat globules are suspended in water; however, it is unstable and separates into two layers

Fat reactions
Fats undergo the same reactions as other esters.
 Transesterification

• with alcohols – alcoholism:

R1COOR2 + R3OH → R1COOR3 + R2OH

• with carboxylic acids – acidisis:

R1COOR2 + R3COOH → R3COOR2 + R1COOH

• with other esters:

R1COOR2 + R3COOR4 → R1COOR4 + R3COOR2

Transesterification reactions are usually used to obtain esters that are difficult to obtain by direct esterification.
 Hydrolysis

fat + water → fatty acid + glycerin

• acid hydrolysis

(RCOO) 3C3H5 + 3H2O → 3RCOOH + C3H5 (OH) 3

• alkaline hydrolysis (saponification)

(RCOO) 3C3H5 + 3NaOH → 3RCOONa + C3H5 (OH) 3

 Unsaturated fat reactions

Unsaturated fats discolour bromine water and potassium permanganate.

Fat hardening
Fat hardening involves the addition of hydrogen to double bonds (→ hydrogenation) occurring in the acid residues of unsaturated fat in the presence of a nickel catalyst. The fat hardening reaction is carried out because of the greater convenience of handling solid fats in everyday life, e.g. during cooking, in technology. This method is used, among others, in the margarine production process.
(C17H33COO) 3C3H5 + 3 H2 → (C17H35COO) 3C3H5
glycerin trioleate → glycerin tristearate