Glutamate: The Fifth Taste

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Glutamate The Fifth Taste

• John Stephenson
• January 22, 2004
• Chee 450

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Monosodium Glutamate

• Sodium salt of glutamic acid
• Odorless fine white crystalline powder, highly
  soluble in water (42g MSG/100g)
• Naturally occurring amino acid
• Non-essential amino acid for humans

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Glutamate Function

• Building block for protein
• Approximately 4lbs of bound glutamate in body
• 50g a day free glutamate produced
• Excitatory neurotransmitter
• Flavor enhancer
• Found naturally in meat, fermented and aged foods
• Umami or Savoriness

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History

• 1,200 years ago Oriental cooks used a soup stock
  from Laminaria Japonica
• 1908 Ikeda isolated glutamate
• Recognized by FDA in 1959 as a safe additive
• Chinese restaurant syndrome

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Production

• Commercial MSG is produced by fermentation of
  starch, sugar beet, sugar cane or molasses.
• 1.5 billion kilograms / year
• Coryneform bacteria commonly used. genus
  Brevibacterium, Corynebacterium or Microbacterium
  (e.g. Corynebacterium glutamicum)

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Corynebacterium glutamicum

• Koryne meaning club
• Bacterion meaning little rod
• Gram ve, catalase ve, aerobic cells

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Overproducing Glutamate

• a-ketoglutarate from citric acid cycle production
  is increased through inhibition of
  a-ketoglutarate dehydrogenase which normally
  forms Succinyl-CoA
• Excess substrate is aminated via glutamate
  transaminase
• Glutamate leaves cell
• Induced by biotin limitation, treatment with
  penicillin or by addition of fatty acid ester
  surfactants. (0.1g -gt 50g/100ml)