Evaluation of free D-glutamate in processed foods

Monosodium glutamate (MSG) is added to many processed foods at significant levels for flavor enhancement. It is also naturally occurring at high levels in some foods. The enantiomeric composition of free glutamate in foods was examined and all foods analyzed were found to contain D-glutamate. The relative percent of D-glutamate in the food products studied depended on the origin of the glutamate. Foods to which MSG was added by the manufacturer had a high total level of MSG but a lower relative percentage of the D-enantiomer (usually less than 0.8%). In comparison, fermented foods tend to have high relative levels of D-glutamate but a lower total amount of the amino acid. The relative percent of D-glutamate in nonfermented foods containing no added MSG was also found to be low compared to fermented products. In some cases the percent D-glutamate could be related to the relative amounts of other food ingredients such as cheese.