Do amino acids, peptides, proteins and nucleotides have a taste?

! Many chemicals have a taste !

We now know that many chemical compounds have a taste. Some taste sweet, sour, bitter, salty or umami.

Almost all simple carbohydrates or sugars taste sweet to some degree. The disaccharide sucrose contains the monosaccharides glucose and fructose and has the molecular formula C12H22O11, is the molecule humans use or refer to when a sweet tasting dish is created, but the taste of amino acids has also long been described.

The first amino acid isolated through gelatin acid hydrolysis was found to be so sweet that it was considered a sugar (''sucre de gelatin''). Amino acids are present in most foods and influence how delicious, sweet, bitter, good or bad these foods taste. The perceived taste of amino acids can range from sour or umami to sweet and bitter and some of the amino acids also taste mildly sweet.

Solms et al. in 1965 demonstrated that many L-amino acids are characterized by a sweet or bitter taste, while most D-amino acids primarily have a sweet flavor.

Birch et al. in 1989 were able to demonstrate a relationship between the taste of enantiomeric amino acids and their physico-chemical properties, particularly the specific apparent volume, which represents the effective size of solutes in water due to their intrinsic molecular architecture. The amino acids alanine, glutamine, glycine, serine, threonine, and proline, taste sweet, whereas other amino acids are perceived as both sweet and bitter. Glutamate and aspartic acid taste sour.

Kikunae Ikeda in 1908 identified glutamate in the broth from kombu seaweeds as the molecule responsible for the umami flavor.

A few years later, in 1913, the ribonucleotides inosine monophosphate (IMP) and guanosine monophosphate (GMP) were also identified to confer the umami taste. Furthermore, it was noticed that foods rich in glutamate and ribonucleotides taste more intense than foods that contain these ingredients alone. The amino acids arginine, histidine, isoleucine, leucine, methionine, phenylalanine, tryrosine, and valine were found to confer the bitter taste.

Many peptides and proteins can have different types of taste as well and many proteins have now been found to taste sweet. For example brazzein is a sweet-tasting protein extracted from the West African fruit of the climbing plant Oubli (Pentadiplandra brazzeana Baillon). Other examples of sweet tasting proteins are curculin, mabinlin, miraculin, monellin, pentadin, and thaumatin.