Umami: Flavour That Attracts Us to Food

When we talk about flavours, it is commonly stated that there are four types of flavours that humans can sense: sweet, salty, sour and bitter. However, there is another type of flavour, for which there are receptors, called umami, and it is the taste of meat. The closest to describing is that it would be the taste of soya sauce. The existence of such flavour and receptors for it is internationally recognized in the academic community in 1987 at the scientific meeting of the Umami International Symposium held in Hawaii.

Which molecules produce umami?

We know that hydrogen ion,  H +, make a sense of sour, some other ions are responsible for salty flavour, sugars are for sweet, but what makes “umami”?

It is a flavor of glutamate, or more precisely, the amino acid L-glutamate and its salts eg. sodium glutamate, the usual food flavour enhancing additive – or various 5′-nucleotides such as guanosine monophosphate (GMP) or inosine monophosphate (IMP).

The “meat”, “spicy” flavour that lasts long in the mouth is due to the existence of a carboxylic acid (RCOO), a derivative of glutamate, which exerts specific receptors on the tongue. The name itself comes from Japanese (う ま 味) and means “a pleasant, spicy flavor”. For example, japanese natto has a umami flavour, as well as soya sauce.

In 1908, Japanese chemist Kikunae Ikeda, who isolated glutamate, and made a name for sodium glutamate – “ajinomoto”, meaning “flavor essence”, started industrial production of glutamate. He is the one who  confirmed that glutamate is responsible for the specific taste of tomato, cheese, meat and certain algae. Then, he came to the hypothesis that people have developed the sensation of this taste when they started eating more proteins.

Kikunae Ikeda wondered what gave that specific taste to dashi, paste for miso, The base for the dashi are brown algae (Phaeophyceae), Laminaria japonica (=Saccharina japonica), also known as “kelp”. He was able to isolate glutamate from the extract of this algae.

About 50 peptides causes sensation of taste. It is interesting to note that the umami balances the taste and that it rounds the aroma of dishes, so this word has become very popular among the chefs. However, if you look at the composition of various spices for food or  chips and other snacks, you will probably find that one of the ingredients is glutamate, usually in the form of sodium glutamate. Glutamate itself is a very important neurotransmitter in spinal cord – about 90% of the synapses in the human brain are glutaminic, and glutamic acid plays an important role in learning and memory.

However, sodium glutamate, like other additives, is on the “black list”: it is linked to the “Chinese restaurant food” syndrome, causing a number of unpleasant symptoms, such as headaches, stomach aches and dizziness, and it has become an undesirable ingredient. It has been shown that glutamate can cause such reactions, but only if it is in high concentrations, above 5 g.

This is really possible: according to FDA data, adults can take up to 13 grams of glutamate per day but should be emphasized that not all of this glutamate is in the form of sodium glutamate. Occasional use of food that contains glutamate, or, the reasonable use of this food additive will not lead to any of the symptoms described. It should also be noted that different people have different tolerances and that asthmatics are more sensitive to sodium glutamate than the rest of the population.

Umami is one of the main reasons why certain types of food attract us and what we enjoy in it.  Also, according to one research, this flavour we feel the best during flights on airplanes:  because of the “white noise” on the flight we lose a sense of other flavors. So, when next time you travel on a plane, order Bloody Mary, which has a lot of aroma  of umami because of tomato. Or a soup.