Described is a method of sanitizing animal carcasses using aqueous streams having an antimicrobial composition added to the stream. Preferably, the antimicrobial composition includes a mixture of one or more carboxylic acids having up to 18 carbon atoms and one or more peroxycarboxylic acids having up to 12 carbon atoms, preferably a mixture of a C.sub.2 -C.sub.4 peroxycarboxylic acid and a C.sub.8 -C.sub.12 peroxycarboxylic acid. Also described is a novel antimicrobial composition adapted for sanitizing animal carcasses containing a mixture of one or more C.sub.2 -C.sub.4 peroxycarboxylic acids and one or more C.sub.8 -C.sub.12 peroxycarboxylic acids and an alpha-hydroxy mono- or dicarboxylic acid.