The use of salt and acids like vinegar in butchering and preparing or long term preserving of foods is a universal European use, not a particularly Jewish one. It was the primary way of handling food before very modern refrigeration. So it was used in kosher butchering, but that is NOT what distinguished it as kosher. It was used by everyone else as well.
Both salts and acids kill and retard the growth of bacteria so it keeps the fresh foods from being contaminated. And preserves foods for longer term use. Think salt pork. Not very kosher. Until the early twentieth century and refrigeration, salted beef(corned beef) and salted pork were carried on ships and eaten in large quantities in cities. Salted hams, pickled pigs feet, and salted chickens. Pickled vegetables, and salted and pickled cabbage [also known as sauerkraut].