Glycine and alanine have a sweet taste, valine and leucine have a bitter taste, and aspartic acid and glutamate have sour and Umami tastes. Though called a bitter amino acid, valine has a slightly sweet taste as well. The sweetness of glycine and alanine is lighter than that of sugar. Combination of amino acids with their respective tastes is a key determinant for the taste of food.
Relationships between amino acids and taste have been explored since the discovery of glutamate as an Umami ingredient. Determination of amino acids contained in foods revealed that the taste we perceive largely depends on the kinds and amounts of the amino acids.

The reason why vine-ripened tomatoes taste good

The taste of tomato mainly consists of two amino acids, organic acids, and sugars. The two amino acids, glutamate and aspartic acid, are essential to the taste of tomato. The ratio of the two amino acids is also important - a glutamate-to-aspartic acid ratio of 4:1 makes the tomato taste the best and brings out the genuine tomato taste.
Young tomato plants bloom with yellow flowers in early summer and then bear small green fruits. Amino acids, together with sugars, increase in amount during the red-ripening process under plenty of sunshine (Figure).
If glutamate is removed from the taste of tomato, it tastes like a diluted apple juice or sour.

Tastes of crab and sea urchin also come from amino acids.

The taste of snow crab consists of just a few kinds of amino acids, nucleic acids, and minerals (Figure). Each of them plays a role of its own. For example, arginine, though a bitter amino acid, brings out a seafood-like flavor, and the Umami of glutamate makes the crab taste like a crab.
The taste of sea urchin mainly consists of 5 amino acids (Figure). If you mix these 5 amino acids in the same proportions as in a living sea urchin, the taste of sea urchin can be excellently reproduced. Methionine, a very bitter amino acid, is the key ingredient for the taste of sea urchin. Without methionine, sea urchins taste like shrimps or crabs.

Fermented food is a treasure house of amino acids.

Human beings have long developed various techniques for harvesting, growing, and preserving food in large amounts. In addition to just storage, we have created dietary culture to eat better by putting some good ideas to cooking and processing.
Among them are fermented foods. Although proteins have no tastes of their own, soybean, fish, and milk proteins are degraded by fermentation to amino acids, producing a wide variety of tastes. Typical fermented foods include miso and soy sauce in Japan, fish sauce and paste in Southeast Asia, and cheese and anchovy in Europe. In addition, there are fermented beans called dawadawa and soumbara in Africa and other traditional fermented foods in other regions.
Fermented foods, easy to preserve and full of enriched tastes, are a treasure house of amino acids. They serve as flavor enhancer and seasoning and make food in each place delicious, unique, and special.

Various fermented foods in the world

Japan	Miso, soy sauce (soybean)	Malaysia	Budu (fish)
China	Douchi (soybean)	Indonesia	Terasi (shrimp)
Thailand	Nann pla (fish)	Europe	Cheese (milk)
the Philippines	Patis (fish)	West Africa	Dawadawa (parkia bean)
Myanmar	Nga-pi (fish)	West Africa	Soumbara (parkia bean)

The world's first non-fattening sweetener has made its debut!

Combination of amino acids with unique tastes of their own infinitely expands the possibility of a new taste or function.
Aspartic acid has a sour taste and slight Umami, while phenylalanine has a bitter taste. However, aspartame, a conjugate of the two amino acids, is 200 times as sweet as sugar.
Metabolized as an amino acid in the body, aspartame helps cut down on calorie intake and has no effect on blood glucose level, although it has a natural taste similar to sugar. Therefore, this sweetener is widely used for various purposes such as calorie control for healthy diet and nutrition control in diabetics.