I can’t tell you how many times I googled this question when I first started taking an interest in making homemade fermented food. Not just any salt will do when it comes to fermenting foods like sauerkraut and kimchi. It’s vital to check the label when selecting salt for fermenting.
First, let’s start with what type of salt you should not use for fermenting foods.
Any type of iodized salt. It’s true that our bodies need small amounts of iodine and iodized salt was created to help combat iodine deficiencies in the 1920s. However, a well-balanced diet today most likely doesn’t have a iodine deficiency. Foods like potatoes, salt water fish, navy beans and even yogurt are good sources of iodine.
The reason you don’t want to use this type of salt for fermenting is because iodine is capable of killing bacteria and will inhibit the fermentation process. In fact, the first thing I ask when helping someone troubleshoot their vegetable ferment is, “does your salt contain iodine?” It is extremely important to avoid any salt that contains iodine when fermenting food as it will most certainly affect the outcome.