The contamination of milk with iodine from iodophors used in milking machine sanitation

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Abstract
The retention and release of iodophor‐derived iodine from milking machine materials was studied using 131I‐labelled iodophor and small tubes of materials used in the construction of milking machines. After one hour's exposure to this iodophor, plastic retained 56% of the 131I label, followed by silicone rubber (31%), rubber (18%), steel (2%) and glass (0.5%). Water rinsing after exposure to iodophor reduced these values to 49%, 26%, 14%, 0.5% and 0.3% respectively. When the tubes were exposed to the iodophor and subsequently rinsed with milk, rubber released the largest amount of iodine into milk (0.099 μg I cm−2), followed by silicone (0.038 μg I cm−2), plastic (0.010 μg I cm−2), glass (0.009 μg I cm−2) and steel (0.002 μg I cm−2). The contact time of iodophor with a particular material influenced both the amount of iodine adsorbed, and the amount subsequently released into milk. The importance of iodine adsorption and desorption phenomena in contributing iodine to milk was compared to that iodine in milk arising from inadequate drainage of iodophor solution from a milking machine, and found to be comparable in magnitude.