A dicarboxylic compound of the general formula HOOC(CH2)nCOOH where n is an integer ranging 11-14, or its alkali metal salt, form an antibacterial agent which is stable in an aqueous solution. Small additions to foods result in an improved antibacterial effect on gram-positive bacteria such as Staphylococcus aureus and Bacillus subtilis. The compound or a mixture of 2 of these compounds can be incorporated into bread or soy cake, etc.