Fluff: Do you buy regular or iodized salt?

It appears all the time in American recipes - so what is kosher salt, and can we get it in Australia?

If you’ve made a Yotam Ottolenghi recipe, or just about any recipe from an American chef, chances are you’ve spied "kosher salt" in the ingredients list, wondered what it is, substituted whatever salt you’ve got in the pantry, and quickly forgotten about it. But was that the best option?

Here's the lowdown on what is actually not a specialty Jewish salt, and not necessarily even kosher.

Why is it called kosher salt?
Although commonly known in the US as kosher salt, the name is actually shortened from koshering salt and therein lies the clue to what it is.

This type of salt was commonly used in the koshering process of removing blood from meat, in accordance with Jewish dietary laws, and the name stuck. It is made up of coarse particles, quite different to the small uniform cubes of table salt. The absorbant kosher salt flakes cling to the surface of the meat, and are more effective at drawing out moisture.

The main point of difference of kosher salt is its shape, and this is also the reason why chefs love to use it. The large particles are much easier to pick up and use between your fingers, which gives you greater control over seasoning when cooking. Because it sticks to the surface of food, it allows for a more even distribution, and it also gives you a visual reference of how much salt you’ve added before it dissolves.

The other selling point of kosher salt is that it is a purer product, because it is not iodised. Just as fluoride is added to water in a widespread health initiative, table salt is fortified with potassium iodide to help combat iodide deficiency disorders. While beneficial for your health, potassium iodide needs to be stabilised with other chemicals once added to salt, and these additions are thought to impact the flavour and reduce the purity of the product.

Kosher salt isn’t necessarily even kosher
Confusingly, there is a difference between kosher-certified salt – salt that meets kosher guidelines – and kosher salt.

Pure salt is kosher, but the production process can alter this. Kosher salt isn’t necessarily always kosher certified, but most brands are and will specify on the package.

How is it used?
Kosher salt is relatively inexpensive, and is considered to be a general, all-purpose cooking salt in American kitchens, rather than a fancy finishing salt.

A key reason why recipes specify a type of salt is because different salts have different densities, and so you can’t use them measure for measure. In some dishes it won’t matter, in others, it will.

Specifying the type of salt keeps everyone on the same page, and if the recipe writer uses kosher as their go-to salt, that’s what they will specify.

There are two key, competing brands of kosher salt in the US: Morton, and Diamond Crystal.While both are ‘kosher salt’, they’re actually quite different products. Diamond Crystal has more of a flattened pyramid shape, while Morton comes in flakes, and is almost twice as dense – in other words, a teaspoon of the latter will be saltier than the first. This is why recipes sometimes even specify one brand or the other.

What can I substitute?
Australian recipe writers tend to call for sea salt, or sea salt flakes.

Ground sea salt and table salt are denser than kosher salt, so you can use a little less if substituting these products. A teaspoon of ground sea salt or table salt is equivalent to approximately 1¼tsp Morton Coarse Kosher Salt, or 1¾ tsp of Diamond Crystal Salt.

Salt flakes
You can use sea salt flakes (such as Maldon sea salt) as you would kosher salt – it just costs more, because it’s considered a finishing salt. You’re paying for its beautiful texture and crunch, which is lost once it dissolves. You can also find kosher salt sold by a small number of specialist retailers in Australia.

At the end of the day, the key difference between all these salts is shape. Once dissolved, it’s all just sodium chloride.