Determination of Iodide in Milk Using the Iodide Specific Ion Electrode and its Application to Market Milk Samples

The iodide specific ion electrode was used to measure the iodide content of raw and commercially processed whole and skim milks. Average iodide values for raw milk and commercially processed milks were 220 and 620 μ g/L, respectively. The specific ion electrode can also be used to measure iodide in milk contaminated with iodophor sanitizing agent since the milk converts iodophor titratable iodine to the ionic iodide. Since free sulhydryl groups are also detected by the iodide electrode, the effects of heating milk on free sulfhydryl formation and electrode activity were established. These data indicate that in conventionally pasteurized milk, sulfhydryl groups are non-reactive and are not detected by the iodide electrode. However, the increase in free sulfhydryl formation was reflected by an increase in iodide electrode activity at temperatures above those of pasteurization. Whereas the iodide specific ion electrode has been previously used successfully to measure iodide content of raw milk, this method has now been shown to be applicable to pasteurized milk if the conventional pasteurization time-temperature relationship of accepted public health standards is not exceeded.