A method of controlling microbial contamination of poultry carcasses in the processing of poultry as food products is described. The method comprises contacting the carcasses with an aqueous medium containing an effective microbial inhibiting amount of active bromine resulting from the addition to the medium of (i) at least one 1,3-dibromo-5,5-dialkylhydantoinin which one of the alkyl groups is a methyl group and the other alkyl group contains in the range of 1 to about 4 carbon atoms or (ii) a solution thereof, or (iii) both of (i) and (ii). Such contacting inhibits contamination of the carcasses by microorganisms, even at least some bacteria that are resistant to antibiotics or antibacterials. Also described are improvements in a poultry chill tank containing an aqueous medium and a plurality of poultry carcasses in contact with the medium. Such improvements result from the presence in the medium of an effective microbial inhibiting amount of active bromine in the medium, which amount results from the addition to water before it enters the tank or while it is in the tank, or both, of (i) at least one of the above 1,3-dibromo-5,5-dialkylhydantoins, and/or a solution thereof.