Recently, @Lisa_Amarna asked me this question on Twitter:

Any idea why there is sugar or dextrose in my table salt?

Hmm..this would make a perfect trivia question, I thought. So I decided to do some research and post an answer here.

Turns out that dextrose is added to iodized salt to make it stable against oxidation in air. Iodide in the form of potassium iodide provides protection against iodine deficiency known to cause goiter which is a disease of the thyroid gland.

According to the Salt Institute, potassium iodide is added to salt in a very small amount – 0.006% to 0.01%, which is about 6 – 10 mg per 100 g of salt. Dextrose is added at a level of about 0.04% to stabilize the potassium iodide.

Potassium iodide, if not stabilized, goes through a chemical reaction called oxidation when it comes in contact with oxygen from the air. Iodide is converted to iodine, which will cause the salt to turn yellowish or red and develop a bad taste. Dextrose does the trick by converting the iodine back to the colorless iodide form.

If you dig chemistry, and want to do a fun exercise at home with your kids, you can actually test if your salt contains iodide or not. Check this “classroom activity” to test for iodide in table salt:

1. Add 4 tbsp iodized table salt to 250 cc water and stir with a spoon for about a minute. Don’t worry if not all of the salt is dissolved
2. Add 1 tbsp of white vinegar, 1 tbsp of 3% hydrogen peroxide and 1/2 tsp laundry starch solution and stir the mixture
3. Let it stand for a minute or so. If the table salt really contains iodide, the solution should turn into blue because the iodine forms a blue color complex with the starch.

You can do the same activity with other types of salts – pickling salt, kosher salt, sea salt and rock salt.

Go ahead, give it a try and let me know how it goes!

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