Glutamates enhance flavors like umami, making them invaluable in cuisine. One of the best known forms is monosodium glutamate (MSG), often used in food to lift flavors. In the body glutamate is synthesized by brain cells.
Necessary for protein synthesis, glutamates are salts and esters of glutamic acid. These compounds belong to a larger family of amino acids.
Glutamates create the umami taste, often described as savory or meaty. This distinction places umami alongside sweet, sour, salty, and bitter as one of the five basic tastes.
Glutamate can be synthesized by the body, unlike amino acids which must be obtained from food. Glutamate is made within cells using simpler molecules.
Common precursors include glucose and amino acids like proline and ornithine. At physiological pH (around 7.4), glutamic acid loses a proton to become glutamate. Glutamate is made and recycled by glial cells of the brain.
Glutamate is found in all organisms, from bacteria to plants and animals. It exists both freely within cells and as a constituent of proteins. Sources of glutamate include:
Plant-Based Foods: Tomatoes, mushrooms, seaweed, aged cheeses, soy sauce, and yeast extracts are particularly rich in free glutamate.
Animal-Based Foods: Meat, poultry, fish, eggs and dairy products also contain glutamate, both bound in proteins and as free glutamate. 100 grams of parmesan cheese has about 1200 mg of glutamate.
Human Body: Glutamate is a core component of proteins and helps regulate brain chemistry.
Glutamates are also produced through fermentation. Foods like soy sauce, miso, and cheese rely on fermentation, which raises glutamate levels.
Functions of Glutamate in Cells
Protein Synthesis: Glutamate is one of the 20 amino acids used to build proteins in cells.
Nitrogen Metabolism: It's central to nitrogen transport and disposal, helping maintain nitrogen balance.
Precursor Molecule: Glutamate is a precursor for the synthesis of other important molecules, including:
Glutamine: Another amino acid active in nitrogen transport and protein synthesis.
GABA (gamma-aminobutyric acid): An inhibitory neurotransmitter in the brain.
Glutathione: Antioxidant.
Energy Production: Glutamate can be converted into alpha-ketoglutarate, an intermediate in the citric acid cycle (Krebs cycle), which is involved in cellular respiration and energy production.
Neurotransmitter: In the nervous system, glutamate is the primary excitatory neurotransmitter, essential for learning, memory, and synaptic plasticity. It enables communication between neurons.
Glutamate in Nature and the Environment
Nitrogen Cycle: Glutamate is a key component of the nitrogen cycle.
Plant Growth: In plants, glutamate is involved in nitrogen assimilation and the synthesis of various metabolites essential for growth and development.
Microbial Metabolism: Glutamates are nitrogen sources important to many microorganisms, such as Bacillus subtilis, found in the GI tracts of humans and cows.
Glutamate in Cuisine
Glutamate dissolves easily in water to blend well and effectively enhance flavors, deepening tastes in broths and simmered stews.
Flavor Enhancement: Glutamates enhance flavor by stimulating glutamate receptors on the tongue, which signal the umami presence to the brain. They also synergize with other flavor compounds, such as nucleotides.
Monosodium Glutamate (MSG): MSG is the sodium salt of glutamate, produced through a fermentation process. It's often added to food to enhance its taste.
Naturally Occurring Glutamate in Foods: Foods naturally high in glutamate also contribute to umami flavor. Culinary processes fermentation, aging and drying increase the free glutamate, intensifying the savory taste, for example in old cheese.
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