Umami

from Wikipedia, the free encyclopedia
Parmesan is a milk product that, as a result of fermentation, contains 1–3% glutamate. In humans, it can also induce the taste perception umami via sensory cells in the taste buds .

The loan word umami (from Japanese う ま 味 umami 'palatability', to う ま い umai 'tasty, spicy' and 味mi 'essence') is used in physiology to denote a quality of the sense of taste that, along with sweet , sour , salty and bitter, is one of the basic Sensory qualities of gustatory perception counts in humans and is described as "meaty", "spicy" or "tasty".

The umami taste is triggered by the amino acid ions glutamate and aspartate as well as by the nucleic acid ions inosinate and guanosinate . This does not include a separate detection of fatty acids released from fats. The taste quality umami corresponds to certain chemoreceptive sensory cells in the taste buds of the tongue with a specific taste receptor, consisting of the two proteins T1R1 and T1R3 in the cell membrane of the taste cells .

Taste cell receptors

The receptor proteins of these taste cells are a heterodimer of two proteins called T1R1 and T1R3, similar to the receptor for the taste quality sweet, which consists of the proteins T1R2 and T1R3. All of these proteins are class C G-protein coupled receptors (C-GPCR). These receptors contain a so-called Venus flytrap domain on a transmembrane domain . The receptors for the umami taste also include the metabotropic glutamate receptors mGluR4 and mGluR1 . The complex of T1R1 and T1R3 recognizes some nucleotides and amino acids with high specificity, in addition to aspartic acid in particular glutamic acid .

One half of the umami taste receptor, T1R3, is also used as a component of the sweetness receptor, in which it forms a heterodimer with T1R2 . By binding to T1R3, the inhibitor lactisol reduces both umami and sweet taste sensitivity in humans . Receptors from the CaSR group bind calcium ions and intensify the sensory impressions umami, sweet and salty.

Taste-inducing substances

Glutamate zwitterion
at pH 7.4 with the side chain in blue
Inosine monophosphate as sodium salt ( disodium inosinate )
Guanosine monophosphate as the sodium salt

The term “glutamate” is used to simplify colloquial terms, but it is a matter of various salts and the anion of glutamic acid , which as an amino acid is a natural component of many proteins in all living things. An umami taste is primarily caused by salts of glutamic acid, more precisely by the anion of glutamic acid that is formed from them in aqueous solution. Glutamic acid is therefore found in foods containing meat, fish and milk, as well as in vegetables and algae. The free glutamates contained in the prepared dishes and, to a lesser extent, aspartates address the receptors of umami taste cells by binding them to them. Aspartic acid is about a quarter as powerful as glutamic acid in terms of umami taste. So far, 52 peptides have been described that produce an umami taste. The anions of the relatively rare amino acids homocysteic acid , cysteine-S-sulfonic acid and ibotenic acid , which are not found in proteins , have a similar effect to glutamate. Also Tricholomasäure active in the fungus Tricholoma muscarium naturally occurring, generates an umami taste.

The main carrier of the umami taste is the free anion of the amino acid glutamic acid , which is extracted from the proteins by proteolysis . Glutamic acid forms the physiologically relevant glutamate zwitterion that occurs in aqueous solution . Their salts are known as glutamates. The sodium salt of glutamic acid is monosodium glutamate (MSG, engl. Monosodium glutamate , MSG), while the potassium salt of glutamic acid as monopotassium glutamate is referred to. Both salts dissociate in aqueous solutions to form sodium ions or potassium ions and the anion of the carboxylic acid group of glutamic acid. At lower pH values (by adding acids ) the umami taste decreases due to the protonation of the carboxylic acid group. A pure glutamate solution is not perceived as tasty, but only in combination with aromas and table salt .

In addition, act purine - ribonucleotides as occurring in aqueous solutions inosine monophosphate (IMP, inosinate), guanosine monophosphate (GMP, Guanosinat) and the degradation to inosine monophosphate indirectly adenosine monophosphate (AMP, Adenosinat) synergistically reinforcing with glutamates. In dry form, these are also available as sodium or potassium salts, as are glutamate and aspartate. Various types of similarly constructed taste receptors in the taste cells of the tongue can contribute to the gustatory perception of glutamates . The palatability impression of glutamate is enhanced by these purines, as they also dock on the glutamate receptor. The maximum umami flavor effect of a mixture of monosodium glutamate and sodium inosine monophosphate is achieved between 30 and 70% of one of the two ingredients. Without the addition of inosine monophosphate, the lower limit of perception of an aqueous solution of monosodium glutamate is 0.12 g / L. In the presence of 2.5 g / L (corresponding to 5  mM ) inosine monophosphate, the lower limit of perception of an aqueous monosodium glutamate solution is 0.0019 g / L.

Glutamate does not reinforce (synergistically) other flavors when it is used in combination with other taste-inducing substances. An aqueous 5 mM monosodium glutamate solution increases the lower limit of perception for acids by about twice. An aqueous 5 mM inosine monophosphate solution increases the lower limit of perception for acids by about thirty times and for bitter substances by about four times.

Gustatory perception

The signals from the taste cells are transmitted to the endings of assigned nerve cells and passed on to the brain via their extensions - as the taste fibers of cranial nerves . The in Mark brain lying nuclei ( nucleus tractus solitarius ) serve for the further course as a changeover point. From here there are pathways through which the hypothalamus and regions of the limbic system can be reached via the pons . On the other hand, projections lead via the thalamus to areas of the postcentral gyrus and the insula of the cerebral cortex. It is only at the level of the cortex cerebri that perceptions that can be communicated verbally, for example as a “tasty” impression of a food, are possible. The umami taste increases both appetite and the feeling of satiety .

Glutamates as flavorings

Occurrence of glutamates

Dried tomatoes create an umami flavor
Soy sauce is an umami-flavored condiment

The amino acid glutamic acid occurs in all living things as a component of proteins. Accordingly, glutamates are found in all protein-containing foods. Glutamic acid is released from proteins by protein-degrading enzymes . The release from the cells of a food is increased by cooking , drying or fermenting and by the resulting cracks in the cell membranes . In general, the glutamate content increases with the degree of maturation of the food to. In cheese, the glutamate content increases with the maturation time due to the breakdown of protein by bacteria and fungi, in air-dried ham due to the protein-degrading enzymes contained in the food in the course of autolysis .

Especially abundant are glutamates in fully ripe and especially dried tomatoes , meat , shiitake , cheese (particularly parmesan ), condiments and sauces (eg. As soy sauce , fish sauce , broth , Fond , meat extract , hydrolysates of proteins, yeast extract , Maggi spice , Celery seed ) as well as in human breast milk . Glutamic acid is the most abundant amino acid in human breast milk. Glutamic acid is particularly used in the food industry, where it is biotechnologically produced and used as a flavor enhancer. Salts of glutamic acid such as monosodium glutamate (MSG) are also produced industrially and widely used as additives from the group of flavor enhancers in foods. In western Europe in particular, consumers would like to see less use of such substances, as consumers do not consider them to be natural, even if they are organically produced and are natural according to the definition of the legislators. Added pure glutamic acid or its salts are mainly used in Asian cuisine and in the industrial production of ready-made foods . In the case of pre-prepared foods, it is supposed to compensate for the loss of taste caused by cooking , sterilizing and freezing . Glutamates are able to hide possible taste defects that can result from too long storage or from food spoilage . The world market for industrially produced monosodium glutamate was around 2 million tons in 2009.

Glutamate in foods
Food of
animal origin		 Glutamate
mass fraction in%
Ham , dried 0.337
Duck meat 0.069
Chicken 0.044
beef 0.033
pork meat 0.023
Chicken egg 0.023
Lamb 0.008
sardine 0.280
Squid 0.146
Scallop 0.140
sea ​​urchin 0.140
oyster 0.130
Mussel 0.105
caviar 0.080
King crab 0.072
Niboshi (dried sardines) 0.050
shrimp 0.040
mackerel 0.036
Bonito flakes 0.036
Tuna , dried 0.031
Salmon caviar 0.022
salmon 0.020
Crayfish 0.019
cod 0.009
lobster 0.009
herring 0.009
Breast milk 0.019
goat milk 0.004
Cow's milk 0.001
Parmesan cheese 1-2.7
Roquefort cheese 1.280
Gruyere cheese 1.050
Stilton cheese 0.820
Cabrales cheese 0.760
Danablu cheese 0.670
Gouda cheese 0.460
Camembert cheese 0.390
Emmental cheese 0.308
Cheddar cheese 0.182
Food of
vegetable or fungal
origin		 Glutamate
mass fraction in%
Tomato , dried 0.648
Green tea 0.450
tomato 0.246
Potato , cooked 0.180
potato 0.102
Corn 0.130
broccoli 0.115
pea 0.106
Lotus root 0.103
garlic 0.099
Chinese cabbage 0.094
Soybean 0.066
onion 0.051
White cabbage 0.050
Asparagus , green 0.049
spinach 0.048
Lettuce 0.046
cauliflower 0.046
Asparagus , white 0.036
Green tea , roasted 0.022
zucchini 0.011
Paprika , green 0.008
Cucumber 0.001
Shiitake , dried 1.060
Shiitake 0.071
mushroom 0.042
truffle 0.009
walnut 0.658
strawberry 0.045
Apple juice 0.021
pear 0.020
avocado 0.018
kiwi 0.005
Bunch of grapes , red 0.005
Apple 0.004
Konbu , dried 1.4-3.2
Nori 1.378
Wakame 0.009
Food
after fermentation 		Glutamate
mass fraction in%
Soy sauce , korean 1.264
Soy sauce , chinese 0.926
Soy sauce , japanese 0.782
Soumbala 1,700
Douchi (black beans) 1.080
Miso 0.5-1
Tempeh 0.985
Natto 0.136
sake 0.186
Anchovies 1,200
Fish sauce , Japanese 1.383
Fish sauce , Vietnamese 1,370
Fish sauce , Thai 0.950
Fish sauce , chinese 0.828
Garum 0.623

Ribonucleotides in foods

Food of
animal origin		 IMP
mass fraction in%		 GMP
mass fraction in%		 AMP
mass fraction in%
beef 0.070 0.004 0.008
pork meat 0.200 0.002 0.009
Chicken 0,201 0.005 0.013
Breast milk 0.0003 unknown unknown
Squid unknown unknown 0.184
tuna 0.286 unknown 0.006
salmon 0.154 traces 0.006
cod 0.044 unknown 0.023
mackerel 0.215 traces 0.006
Scallop unknown unknown 0.172
lobster traces traces 0.082
shrimp 0.092 traces 0.087
crab 0.005 0.005 0.032
Anchovies 0.300 0.005 unknown
sardine 0.193 unknown 0.006
sea ​​urchin 0.002 0.002 0.010
Food of
vegetable or fungal
origin		 IMP
mass fraction in%		 GMP
mass fraction in%		 AMP
mass fraction in%
tomato unknown unknown 0.021
Tomato , dried traces 0.010 unknown
Potato , cooked traces 0.002 0.004
pea unknown unknown 0.002
Asparagus , green traces traces 0.004
Nori 0.009 0.005 0.052
Shiitake , dried unknown 0.150 unknown
Porcini mushroom , dried unknown 0.010 unknown
Oyster mushroom , dried unknown 0.010 unknown
Morel , dried unknown 0.040 unknown
Enoki unknown 0.022 unknown

Side effects of glutamates

Since 1969, monosodium glutamate has been suspected of causing side effects in higher doses, such as headaches or body aches, the so-called China-Restaurant-Syndrome . However, previous studies have not been able to prove that glutamates that are additionally consumed with food can lead to the symptoms described. In a meta-analysis, no connection was found between foods rich in glutamate and headaches. In the studies that found a connection between glutamate and headache after administration of pure glutamate solution without food, deficiencies in the studies were found in the double-blind control, as the test subjects were able to differentiate between receiving a glutamate solution or a glutamate-free control solution . In addition, a connection between glutamate and asthma was described and subsequently examined, but the described connection could not be confirmed in a meta-analysis.

Since monosodium glutamate occurs in all protein-containing foods, the statement “without monosodium glutamate” used for clean labeling is incorrect and has been described as misleading. The statement “without the addition of monosodium glutamate” used next to it was described as misleading and increased the concerns of some consumers about glutamate.

history

As early as the fifth century BC, Confucius described the use of a fermented condiment made from meat, grain, salt water and ethanol in China. From around 200 BCE onwards, fermented soybeans were used for seasoning. In ancient Rome was one as garum or Liquamen called seasoning sauce containing also fermented fish, used 200 BCE from about the year. Since the 15th century the spicy fish sauce is used every day in Southeast Asia .

Kikunae Ikeda (1864-1936)

The name umami goes back to the Japanese chemist Kikunae Ikeda , who, based on his own taste experiences, suspected a fifth basic quality of taste in addition to the four sensibilities for characteristics of sweet, sour, salty and bitter in a food. In 1909 he suggested “umami” as a name for this after he had identified glutamic acid as its main flavor carrier - in the extract of kombu , a component of traditional dashi made from Japanese seaweed ( Laminaria japonica ) .

In the same year Ikeda and a business partner began the industrial production of monosodium L -glutamate , obtained from the hydrolyzate of wheat proteins . The gluten was hydrolyzed under the action of hydrochloric acid and split into its amino acids, over a third of which is glutamine and glutamic acid . They brought the crystallized salt of glutamic acid onto the market as a sprinkleable seasoning under the trade name “Aji-no-moto” ( 味 の 素 'Essence of Taste'). It found growing popularity in East Asia, similar to “ Maggi ” previously in Central Europe; The company evolved into a group that has been called Ajinomoto since 1946 and which today operates worldwide. The complementary effect of purine nucleotides such as inosine monophosphate was first described in 1913 by Shintaro Kodama in extracts of bonito flakes .

literature

Individual evidence

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