A process for preparing a biocidal composition comprising the steps of: (i) dissolving at least one polyol in water to form a water/polyol co-solvent solution； (ii) adding at least one organic acid to the water/polyol co-solvent solution； (iii) adding at least one stabiliser to the water/polyol co-solvent solution； (iv) adding a flavonoid composition comprising at least one flavonoid selected from the group consisting of: poncirin, neoeriocitrin, isonaringin, rhoiflin, naringen, neodiosmin, hesperidin, neohesperidin and naringenin.
