Glutamic Acid in Food and its Thermal Degradation in Acidic Medium

Glutamic acid is an amino acid naturally occurring in many foods and it is responsible for umami taste. For this reason, it has been widely used as a food additive and flavor enhancer as monosodium glutamate. Glutamic acid is stable under standard conditions. However, high temperature or extreme pH conditions may induce racemization. In addition, it is a good substrate for non-enzymic browning reactions (Maillard reaction).A case study of the glutamic acid thermal degradation at acidic pH was carried out. Different grape musts were subjected to heating at 90 °C for 30 h by means of a lab-scale equipment emulating a real process. Model solutions were utilized to gain a deeper comprehension of this phenomenon and to explain the glutamic acid degradation pattern. Results showed that glutamic acid underwent degradation during grape must cooking, following the same trend observed in the model solutions. The amino acid was almost linearly reduced throughout all the cooking procedure yielding pyroglutamic acid as the main product of degradation.