Iodine Stability in Salt Double-Fortified with Iron and Iodine

Abstract

Deficiencies in small quantities of micronutrients, especially iodine and iron, severely affect more than a third of the world's population, resulting in serious public health consequences, especially for women and young children. Salt is an ideal carrier of micronutrients. The double fortification of salt with both iodine and iron is an attractive approach to the reduction of both anemia and iodine-deficiency disorders. Because iodine is unstable under the storage conditions found during the manufacturing, distribution, and sale of salt in most developing countries, the effects of packaging materials and environmental conditions on the stability of salt double-fortified with iron and iodine were investigated. Salt was double-fortified with potassium iodide or potassium iodate and with ferrous sulfate or ferrous fumarate. The effects of stabilizers on the stability of iodine and iron were followed by storing the salt under three conditions that represent the extremes of normal distribution and sale for salt in developing countries: room temperature (25 degrees C) with 50%-70% relative humidity, 40 degrees C with 60% relative humidity, and 40 degrees C with 100% relative humidity. The effects of stabilizers, such as sodium hexametaphosphate (SHMP), calcium carbonate, calcium silicate, and dextrose were investigated. None of the combinations of iron and iodine compounds was stable at elevated temperatures. Essentially all of the iodine was lost over a period of six months. SHMP effectively slowed down the iodine loss, whereas magnesium chloride, a typical hygroscopic impurity, greatly accelerated this process. Calcium carbonate did not have a sparing effect on iodine, despite contrary indications in the literature. Ferrous sulfate-fortified salts generally turned yellow and developed an unpleasant rusty flavor. Salt fortified with ferrous fumarate and potassium, iodide was reasonably stable and maintained its organoleptic properties, making it more likely to be acceptable to consumers. We confirmed that application of the iodine compounds as solutions resulted in a more even distribution of the iodine throughout the sample. The effect of the packaging materials was overshadowed by the other variables. None of the packaging materials was clearly better than any other. This may have been due to the fact that the polymer bags were not heat sealed, and thus some moisture penetration was possible. The results indicate that with careful control of processing, packaging, and storage conditions, a double-fortified salt could be stabilized for the six-month period required for distribution and consumption. Unfortunately, the processing and storage required are difficult to attain under typical conditions in developing countries.

Iodine stability in iodized salt dual fortified with microencapsulated ferrous fumarate made by an extrusion-based encapsulation process

“…(1) and (2), ferrous iron compounds can reduce iodate, forming the volatile elemental iodine (Diosady et al, 2002a). Iodized salt loses iodine due to interactions with salt impurities, and the environment.…”

“…Indian scientists from the National Institute of Nutrition (NIN) first initiated research on double fortification of salt and made prominent contributions to this area (Mannar et al, 1989;Narasinga Rao, 1990). However, the formulations developed in these early studies were not technically or commercially feasible (Diosady et al, 2002a).…”

Addressing the Challenge of Iodine Deficiency in Developing Countries

“…As these openings are never closed, it is a feasible supposition that the high ambient temperature and humidity/moisture prevailing in these tropical countries may cause iodine levels in the salts to wane with the passage of time. 15,16 These unfortunate practices on the part of consumers inadvertently negate any investment made by the iodized salt manufacturers. This could be prevented by encouraging salt manufacturers to package their products in easy to reseal cartons and/or re-sealable plastic containments.…”

A study of storage and distribution of double fortified salts in Kenya

“…doi:10.1016/j.jfoodeng.2005.05.057 regional consumption (Narasinga Rao & Vijyasarathy, 1975;Zoller et al, 1980). Emboldened by the progress made with the iodization (USI) programme, we as well as others have been examining the feasibility of fortifying salt with iron along with iodine (Diosady, Alberti, Ramcharan, & Venkatesh Mannar, 2002;Hurrell, 2002;Zimmermann et al, 2002). The physical and social infrastructure developed for the salt iodisation programme should facilitate putting in place a cost-effective method of delivering adequate levels of iodine and iron in double fortified salt to the affected populations.…”