Physical Properties of Amino acid:-
Solubility: Amino acids are readily soluble in water, slightly soluble to insoluble in ethanol and insoluble in ether. Tyrosine is soluble in hot water but only sparingly soluble in cold water. Cysteine with difficulty is soluble in only hot water. Proline and hydroxy proline are soluble in alcohol and ether.
Amino acids are generally soluble in acids and bases and form salts. Tyrosine is moderately soluble in acids and bases. Cysteine is soluble in strong mineral acids (HCI) but slightly soluble in acetic acid and dilute ammonia.
Melting Points: Amino acids have a high melting points in the range of 200 - 300°C.
Taste: Amino acids are usually sweet, tasteless or bitter. Eg. Gly, Ala, Val, Pro, hydroxy-Pro, Ser, Try and His are sweet; Leu is tasteless, whereas, Ile and Arg are bitter in taste.
Sodium salt of glutamic acid (Monosodium glutamate, MSG, also known as Ajinomoto) is valuable as a flavouring agent for certain foods and sauces since it imparts and enhances the flavour (also for meat and meat products). MSG is being used since 1908 when a ~apbese Chemist Kikunae Ikeda discovered that MSG could improve the flavour of the food products. However, tests on animals have shown that it can cause brain damage and cancer. It has not been proved to be dangerous to humans. However, food experts do not approve its use for infants and pregnant women. The acceptable daily intake of MSG for a person weighing about 60 Kg is approximately 7.2 gms.