FIELD: agriculture. SUBSTANCE: invention relates to technology of post-harvest treatment of food grains before storage using organic preserving agents. Method involves treatment of food grains in electromagnetic field of microwave with propionic acid that comprises chitosan addition. The preparation obtained by sequential extraction of biomass of micromycetes Mortierella nantahalensis with a nonpolar extractant in supercritical state, water, alkali, water, acid, water, alkali and water is used as chitosan source followed by combination of the first extract with solid extract. Invention provides enhancing safety in food grains storage. EFFECT: improved preparing method. 2 ex
