Glutamate is naturally present in most foods, such as meat, seafood and vegetables. Two kinds of nucleotides that contribute most to the umami taste, inosinate and guanylate, are also present in many foods.
Inosinate is found primarily in meat and fish whereas guanylate is more abundant in the mushroom family such as dried shiitake mushrooms. In addition, the umami scores in foods are found to increase due to
maturation. Tomatoes and cured ham are typical of this. Due to maturation, the glutamate in tomatoes increases and reaches its highest when tomatoes turn very red.