穀氨酸
Yeast extracts consist of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture media. They are often used to create savory flavors and umami taste sensations, and can be found in a large variety of packaged food, including frozen meals, crackers, snack foods, gravy, stock and more. They are rich in B vitamins (but not B12), and so are of particular importance to vegans and vegetarians. Yeast extracts and fermented foods contain glutamic acid (free glutamates), an amino acid which adds an umami flavor. Glutamic acid is found in meat, cheese, fungi (mushrooms), and vegetables—such as broccoli, and tomatoes.