Stability of Iodine in Iodized Fresh and Aged Salt Exposed to Simulated Market Conditions

Background The salt iodization law of the Philippines required that iodized salt sold at retail not be exposed to direct sunlight, high temperature and relative humidity, and contamination with moisture and dust from the environment. However, because the majority of local consumers buy salt displayed in open heaps, it was suggested that iodized salt should be sold in the same manner for greater accessibility and availability. Objective We aimed to provide evidence on the stability of iodine in local aged and fresh salt iodized at 100 ppm iodine and exposed to various market and storage conditions. Methods Samples of salt in open heaps and repacked salt were exposed for 4 weeks, and salt packed in woven polypropylene bags was stored for 6 months. The iodine content of the salt was determined by the iodometric titration method, and the moisture content was determined by the oven-drying method. Results For all types of exposed salt, iodine levels were above 60 ppm after the end of the study (4 weeks). Within each salt type, losses were greater for open-heap salt than for repacked salt. The greatest drop in moisture content occurred in the first week for most types of salt and exposure combinations. Moisture content was linearly correlated with iodine content. Iodine levels in stored salt remained above 60 ppm even after 6 months. Conclusions Iodized salt is able to retain iodine above the recommended levels despite exposure to an open environment and use of ordinary packaging materials while being sold at retail and kept in storage.