How is iodine added to salt

A slide within the feed hopper controls the rate of salt addition. A premix of KIO3 with salt at an approximate ratio of is prepared separately and fed onto the bulk salt at a controlled rate by a rotating arm within a conical feeder, or by a screw within the screw feeder located close to the salt feed hopper above the conveyor.

The salt and premix are mixed as they move up the screw conveyor and the desired content of iodine in the salt is achieved. The mixture is then homogenized by passing through a roll crusher or pin mill that grinds it to a uniform size of mm.

After crushing, the iodized salt is passed through a second inclined screw for further mixing before packing. Drip Feed Addition This process is commonly used for iodization of salt crystals.

The crystals are manually fed into a hopper that discharges at a uniform rate onto a belt conveyor, about cm wide and 5. The conveyor is equipped with a tensioning device. The feed hopper has a capacity of about kg and the rate of salt flow onto the conveyor is controlled by a slide valve.

Flexible rubber curtains on three sides shape the salt into a narrow band cm wide and 2 cm deep on the conveyor belt and prevent it from spilling over the edge.

The KIO3 solution is stored in two litre polyethylene stock tanks with discharge valves at the bottom to permit the filling of two 25 litre feed bottles, mounted to ensure a continuous circulation of solution from the main tank to the feed bottles. Thus the solution continuously drips at the desired rate onto the salt crystals. The iodized salt falls into a discharge hopper for collection in bags.

For continuous operation the hopper should have a twin spout with a diversion valve. Experience has shown that a capacity of 5 tons per hour is ideal for a drip feed system, which requires only a low pressure head to maintain the required flow rate. This method is used in some Asian countries, for example, Indonesia.

The drip feed system is simple and cheap and is often used for iodizing moist crude salt crystals and even refined powder salt. In a simplified system used in India, the drip system is introduced into the feed point of a salt grinder.

The drip feed system followed by grinding often yields consistent iodate dispersion. Spray Mixing Often, iodization is to be integrated with existing salt production and refining systems. Typically salt slurry from a thickener is dewatered in a centrifuge and then dried in a rotary or fluid bed drier.

Into this system a sensor installed on the thickener can send a signal to the solution dosing pump that sprays iodate solution at a rate proportional to the flow rate of solids to the centrifuge. In more conventional operations where refining equipment is not available, salt iodization plants will need to be established. Salt in crystal form is crushed to a coarse powder in a roller mill and manually fed into a feed hopper fitted with a wire mesh screen or grating at the top to prevent large lumps of salt from falling into it.

A second shaft with four plates is fitted in the outlet of the hopper and regulates the flow onto an inclined conveyor belt. Both these shafts are driven by a variable speed drive system and the rate of rotation is adjusted to give the required throughput. The sheet of salt discharging from the belt into the spray chamber receives a fine atomized spray of potassium iodate solution from two nozzles, at a pressure of 1. The spray nozzles are designed to deliver a flattened spray that spreads over the entire width of the salt stream.

The concentration of solution and the spray rates are adjusted to yield the required dosage of iodate in the salt. The iodate solution is kept under pressure in two stainless steel drums, each of about 80 liters capacity. The pressure in the drums is maintained constant by an air compressor with a regulator. The salt with added potassium iodate falls into a screw conveyor cm wide and 2. Travel through the screw provides uniformity of mixing. The screw conveyor discharges into twin outlets where bags are kept ready for filling.

In the U. Although salt iodization never was made mandatory, estimates are that more than 90 percent of U. Other sources of dietary iodine include eggs, enriched grain products and plant foods grown in iodine-rich soils. Unfortified sea salt contains only a small amount of iodine. Iodized salt in the U. As such, the developing fetus and infant are particularly vulnerable to the effects of inadequate iodine nutrition. Prenatal and other multivitamins marketed in the U. Data from the U.

National Health and Nutrition Examination Survey — demonstrated that only A recent survey of prenatal multivitamins available in the U. Levels of urinary iodine cannot be used to determine iodine status in an individual, given the day-to-day variation in dietary iodine intake.

Median urinary iodine levels are used instead and reflect dietary iodine sufficiency across populations [ 5 ]. Subsequent studies have shown that this decrease has stabilized [ 25 , 26 , 27 ], although some subsets of the population, in particular pregnant women and women of childbearing age, may be at risk for mild to moderate iodine deficiency. Iodine deficiency remains one of the most important public health issues globally, and an estimated 2.

In , the United Nations World Summit for Children set forth the goal of eliminating iodine deficiency worldwide [ 29 ], and considerable progress has since been achieved. Other groups which have been instrumental in advocating for improved iodine nutrition have been Kiwanis International and the U. Center for Disease Control [ 16 ].

A public health approach has been used to help ensure adequate iodine intake in U. The U. National Academy of Sciences also advocates that iodine be included in all prenatal multivitamins [ 33 ]. Following the successful implementation of salt iodization program in Switzerland, the introduction of iodized table salt in the U.

However, although recent national studies demonstrate that the general population is overall iodine sufficient, salt iodization in the U. National Center for Biotechnology Information , U. Journal List Nutrients v. Published online Nov Angela M. Braverman , and Elizabeth N. Author information Article notes Copyright and License information Disclaimer.

This article has been corrected. See Nutrients. This article has been cited by other articles in PMC. Abstract Iodine is a micronutrient required for thyroid hormone production.

Keywords: history, iodine, supplementation. Importance of Adequate Iodine Nutrition Adequate levels of iodine, a trace element variably distributed on the earth and found mostly in the soil and water of coastal areas, are required for the synthesis of the thyroid hormones, thyroxine T4 and triiodothyronine T3 , which play key roles in the metabolic processes of vertebrate life.

Sources of Iodine Intake and Exposure Iodine atomic weight Dietary Iodine In the U. Iodine Fortification and Supplementation in the U. Iodized Salt In the U. Iodine in Supplements and Multivitamins Iodine is required for normal brain myelination in utero and during the early post-partum period. Current Status of and Recommendations for Iodine Nutrition Levels of urinary iodine cannot be used to determine iodine status in an individual, given the day-to-day variation in dietary iodine intake.

Iodine added to food. What is iodine? Iodine is a nutrient found in most foods. But it's usually found in only small amounts. Iodine is essential for the brain development of unborn babies and young children. Low iodine levels in a diet can cause: poor growth and development in infants and children thyroid diseases goitre swelling of the thyroid gland in the neck.

How much iodine do you need? The recommended dietary intake RDI for iodine depends on your age and life stage: children over 14 and adults need about micrograms of iodine a day pregnant women need about micrograms breastfeeding women need about micrograms children under 14 need less.

How to get enough iodine in your diet You can get iodine by: eating iodine-rich foods eating food with iodine added. Iodine-rich foods include: milk and milk products eggs seafood foods that contain seaweed, like sushi.

Food with iodine added includes store-bought bread and iodised salt. Pregnant and breastfeeding women need more iodine When you're pregnant or breastfeeding, you need more iodine than normal. Iodine — Ministry of Health Pregnancy and food Foods fortified with iodine Fortification is when extra nutrients such as iodine are added to food and drinks during manufacturing.