Cheese & Preserving Salt, must be large grained, with large faceted crystals, and an open granular structure. The grain size and structure allows it to absorb more moisture than other forms of salt.
Cheese & Preserving Salt contains no iodine. Iodine will kill the lactic bacteria in the aging process of cheese, and it is this lactic bacteria that is so important to the proper aging of your cheese.
Cheese & Preserving salt is used to help in flavour production, preservation and brining your cheese and preserves.
From Green Living Australia.