Pickled mackerel, known as saba no heshiko, is made by fermenting fresh mackerel in salt and rice bran for close to a year. This traditional method of preservation was used after an especially successful catch to store the excess mackerel before it spoiled. With eight times as much glutamic acid as fresh mackerel, pickled mackerel has a unique savory flavor filled with umami. You may find yourself so addicted to this delectable pickle, you ask for second and third helpings of rice to accompany it in the Japanese style!