The composition and properties of the main biogenic compounds (carbohydrates, lipids, amino acids, nucleic acids, proteins, enzymes, etc.) and biochemical processes of synthesis, transformation and decay of organic substances in organisms are considered. The chemical composition of grain of cereal and leguminous crops, seeds of oilseeds, potato tubers, root crops, vegetative mass of fodder herbs, vegetables, fruits and berries, as well as meat, milk and its secondary raw materials is given. Particular attention is paid to the processes that occur during post-harvest ripening, processing, storage and processing of plant products, as well as biochemical and physicochemical changes in milk and meat during heating and mechanical processing, freezing and defrostation, exposure to microorganism enzymes.