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 microwave field with propionic acid that comprises chitosan as an addition. Preparation obtained by sequential extraction of biomass of micromycetes Mortierella gracilis with 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
