“Whomever says ‘Breton’ means salted butter. The primary role of the salt used in this butter was as a preservative, in other words, salt was the first refrigerator in history. How does it work? The fatty molecules in the butter consider the salt as an aggression and their reaction to it is to reject the water they contain, which ages the butter.
This ancestral method was used where the supply of salt was abundant and exempted the products from the gabelle, or salt tax, levied in the West and North of France, two areas of the country which have retained the traditional use of salted butter. Today, a salted butter is defined as one having more than a 3% salt content.”