The principle involved in making these pickles is really quite simple. Pressure is brought to bear upon salted food, causing it to release a certain amount of liquid. This liquid, in turn, becomes the brine in which that food is pickled. In other words, the salt acts as a catalyst, seasoning and preservative. Salted “pressure” pickles are the oldest known form of preserved food in Japan. Although commercially prepared salt pickles are increasingly available, this kind of pickling is basically a home endeavor.