L-Tryptophan 98.5% Feed Grade. Product NameL-Tryptophan(feed grade)Test StandardQ/AFF08-2008,AJI92 ItemStandard dateActual dataDescription:White ... dry, % ≤0.50.14Residue on ignition, % ≤0. 50.1L-Tryptophan is one of essential amino acids in animal and human ... The body uses tryptophan to help make niacin and serotonin. Serotonin is thought to produce healthy sleep and a stable mood. L-Tryptophan