PURPOSE: To prevent rottenness of food with anaerobic bacteria and multiplication of microorganisms causing food poisoning at a low cost and safely without changing physical properties of food by sealing a food together with a deoxidant containing a natural antimicrobial substance extracted from a plant in an air- impermeable container.

CONSTITUTION: A food and a deoxidant containing a natural antimicrobial substance extracted from a plant or the same substance (e.g. allyl isothiocyanate, an antimicrobial substance of Japanese horseradish) chemically synthesized are sealed in a bag in an air-impermeable container or bag. A deoxidant comprising iron powder as a main component is preferable. The container or bag to seal the bag preferably has a permeability to oxygen of ≤50.ml/m2.24 hours atm (20°C). Preservation temperature of food is preferably ≤20°C.