 However, only 5% or more of the glutamate may be the D-enantiomer.Nonfermented naturally-occurring foods have lower relative levels of D-glutamate than fermented products.Glutamic acid stimulates specific receptors located in taste buds such as the amino acid receptor T1R1/T1R3, or other glutamate receptors like the metabotropic receptors (mGluR4 and mGluR1) which induce the flavor profile known as umami.