... glutamic acid through glutamate decarboxylase, GABA, a kind of natural non-protein amino acid, is an important neurotransmitter of ... , dairy products, frozen food, wine, fermented food, bread, soup and other healthy and medical-treating food in Japan and some European ... tea, beverages and milk products. 3. as the natural ingredients used in coffee, chocolate, apple juice, cocoa, yogurt, milk sugar ...