Methods are provided which include steeping and/or spraying a harvested cereal grain, such as barley, wheat, rye, millet, corn (maize), rice, or oats, in or with an aqueous solution including an effective amount of chlorine dioxide to provide a treated cereal grain. The treated cereal grain obtained from chlorine-dioxide steeping and/or spraying generally has a reduced microorganism and/or toxin content, and may be subjected to additional malting processes.