Glutamate flavoring is the generic name for flavor-enhancing compounds based on glutamic acid and its salts (glutamates). These compounds provide an umami (savory) taste to food. Glutamic acid and glutamates are natural constituents of many fermented or aged foods, including soy sauce, fermented bean paste, and cheese. They can also be found in hydrolyzed proteins such as yeast extract. The sodium salt of glutamic acid, monosodium glutamate (MSG), is manufactured on a large scale and widely used in the food industry. Glutamic acid versus glutamates
When glutamic acid or any of its salts are dissolved in water, they form a solution of separate negative ions, called glutamates, and positive ions like H3O+ or Na+. The result is actually a chemical equilibrium among several ionized forms, including zwitterions, that depends on the pH (acidity) of the solution. Within the common pH range of foods, the prevailing ion can be described as −OOC-C(NH+3)-(CH2)2-COO−, which has an electric charge of −1. Only the glutamate ion is responsible for the umami flavor, so the effect does not depend significantly on the starting compound. However, some crystalline salts such as monosodium glutamate dissolve much better and faster than crystalline glutamic acid. This has proven to be an important factor in the implementation of substances as flavor enhancers. Discovery
Although they occur naturally in many foods, glutamic acid and other amino acid flavor contributions were not scientifically identified until early in the twentieth century. In 1866, the German chemist Karl Heinrich Ritthausen discovered and identified the compound.
It is generally associated with high doses (>4 mg/kg per  hour or >67 mcg/kg per minute) and prolonged use (>48 hours)  though it has been reported with high-dose short-term infusions.Additional proposed risk factors include a young age, critical illness, high fat and low carbohydrate intake, inborn errors of mitochondrial fatty acid oxidation, and concomitant catecholamine infusion or steroid therapy. Characteristics of PRIS include acute refractory bradycardia, severe metabolic acidosis, cardiovascular collapse, rhabdomyolysis, hyperlipidemia, renal failure, and hepatomegaly.The incidence of PRIS is unknown, but it is probably less than 1 percent. Mortality is variable but high (33 to 66 percent). Treatment involves discontinuation of the propofol infusion and supportive care. Risk Factors
Predisposing factors seem to include young age, severe critical illness of central nervous system or respiratory origin, exogenous catecholamine or glucocorticoid administration, inadequate carbohydrate intake and subclinical mitochondrial disease. Treatment
Treatment options are limited and are usually supportive, including hemodialysis with cardiorespiratory support. == References ==