Tempeh, a traditional Indonesian fermented soybean food, has recently been focused on among the many fermented
soybean foods, because of its superior nutritive qualities and metabolic regulatory functions (5, 6). Recently, a method of producing γ-aminobutyric acid-enriched tempeh, which has antihypertensive effects, has been reported (7, 8). However,
traditional soybean tempeh (9) is usually formed into a block during the fermentative production process. Since tempeh is
produced using boiled and dehulled soybean without the soybean germ (hypocotyl) that contains a high level of isoflavone, the isoflavone content in tempeh produced tends to be low. In addition, isoflavone with the aglycon form has a
higher absorptivity than that with the glucoside form (10).