Download Umami: The Fifth Taste

Glutamate: The Fifth Taste
John Stephenson
January 22, 2004
Chee 450
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
O
+
H3N
O
O
OH
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
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
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)
Corynebacterium glutamicum
– meaning club
 Bacterion – meaning little rod
 Gram +ve, catalase +ve, aerobic cells
 Koryne
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 -> 50g/100ml)
