Salt is the only rock we eat. It seasons our food and is essential to our health. Knowing the properties of the different varieties of food salt helps us to know what and when to use a particular type, and there is a noticeable difference between pickling and kosher salt.
Why Use Salt at All?
Nutritionally speaking, salt helps us to retain water and adds electrolytes used in the normal functions of our cells and organs. It helps us to maintain the fluid in our blood cells, is used to transmit information in our nerves and muscles and aids in the use of certain nutrients from our small intestines.
In cooking, salt helps make food taste better. It helps draw out moisture when applied to foods, which is necessary when cooking certain food items. In brines, it not only adds flavor but also adds moisture to meat by denaturing water-soluble proteins, trapping water in the meat. It is also a natural preservative, fending off harmful microbes or, in some applications such as making cheese, sauerkraut and bread, limits microbial activity.
Pickling salt is a fine-grain salt with a uniform structure from granule to granule. It contains no iodine or anti-caking additives. Though it is processed, it is pure salt. It is generally used in pickling and canning foods but can also be used for baking. Its fine grain also allows it to easily dissolve in water but also makes it easy to clump when exposed to moisture.
Kosher salt was originally used to "kosher" meats by drawing the blood out. Many cooks like using kosher salt. It is a pure, coarse grain salt with no iodine or anti-caking additives. It has an irregular, flat, flaky shape that helps it to adhere to food. Kosher salt's shape also helps it to dissolve relatively slow compared to a fine-grain salt like pickling salt. Its adhering and dissolving qualities help to pull juices out of meat.
When to Use
Pickling salt can be used as seasoning for French fries and popcorn. Due to the fine grain size, its application won't make eating it feel like there are large, crunchy grains in your mouth. Because pickling salt dissolves easily in water, it can be used to build brines, such as when brining a large pork roast or making your own sauerkraut. It can also be used as a substitute for table salt.
Kosher salt is great for general purposes. You can use it to season almost all of your food before or during the cooking process. For instance, use it to preseason meat, which will help pull out juices and, in turn, help brown the meat during cooking. Kosher salt's coarse grain also makes it easier to control when applying it with your fingers, helping you to more evenly season your food. It can also be used for brines, but you will need a higher volume of kosher salt than pickling salt because kosher salt's grains are bigger and, due to its shape, do not compact like pickling salt. When measuring, use weight instead of volume.
Versus Table Salt
Table salt is a fine-grain salt, and most varieties will contain iodine and anti-caking additives. Iodine was added to salt in the early 20th century. When the body does not get enough iodine, the thyroid gland gets big and forms cysts, which gives the affected person a goiter. However, dietary iodine is found in seafood, so with an ample seafood diet, supplementary iodine by way of table salt is unnecessary.
Due to the addition of iodine, table salt tends to have a less pure taste. It can be bitter and also not react well with certain foods. For instance, table salt with iodine turns pickles dark and it also inhibits bacterial fermentation when making sauerkraut. The anti-caking additive also does not dissolve, so it creates a cloudy solution when used in brines.