Amino acids consist chemically of a carboxylic acid (-COOH) and an amino (-NH2) functional group and can be linked together by a peptide bond to form polypeptides. A polypeptide made of 50 or more amino acids is referred to as protein. These macromolecules (large molecules) are involved in every biological process including cell growth, metabolism, digestion, respiration, and reproduction. Thus, amino acids are the fundamental building blocks of living organisms. Even though there are hundreds of amino acids in nature, only 22 amino acids are required to create all the proteins found in the human body and most other forms of life (Becker & Kleinsmith, 2009).

For the human body only 21 amino acids are relevant and are grouped into essential and non-essential amino acids, distinguishing whether our body can produce those amino acids or not. There are nine essential amino acids that we must eat in our diet, these include: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. The 21st amino acid Selenocysteine also counts as an essential amino acid as food sources with selenium are required for the synthesis of Selenocysteine (Clark & Pazdernik, 2012). Non-essential amino acids include: Alanine, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Proline, Serine, and Tyrosine (Becker & Kleinsmith, 2009).

Amino acids are chiral molecules, which means they exist in two chemically identical but mirror-image versions, also known as enantiomers. The different enantiomers can cause a dramatic effect on the taste perception. In combination with elements such as sodium, potassium, calcium, magnesium, or compounds such as ammonium, amino acids can form various salts. Of particular interest is the sodium salt of glutamic acid, known as monosodium glutamate (MSG) (Mouritsen & Styrbæk, 2014).