Data are presented from studies relating to cleaning and sanitizing reverse osmosis/ultrafiltration equipment used to concentrate and fractionate cheese whey. Current equipment design makes cleaned-in-place (C.I.P.) systems mandatory since modules cannot be completely drained or disassembled. In addition, many presently accepted sanitizing methods cannot be used without harming the delicate membranes. More than 50 different chemical agents, or combinations, currently approved by the Food and Drug Administration, were screened. Grossly contaminated reverse osmosis/ultrafiltration equipment was readily sanitized with several agents, including iodophors (10 ppm available iodine), sodium metabisulfite (0.2%), diethylpyrocarbonate (0.05%), zephirin chloride (0.006%), and calcium hypochlorite (10 ppm available chlorine). Merits of these agents are discussed. The sanitizer of choice would depend on type and design of equipment, operation of the plant, time allotted for cleaning, and degree of control desired. For best results, complete flooding of test equipment was necessary, indicating that sterilization cannot be assured unless modules are mounted in a vertical position.

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