Progress in Research on the Formation Mechanism and Physiological Functions of D-Amino Acids in Foods

Among the 20 proteinogenic amino acids, 19 can exist in two stereoisomeric forms, D- and L-enantiomers except glycine. According to conventional theory, L-amino acids are the main body involved in life activities, while little attention has been paid to the existence and physiological activity of D-amino acids in organisms. With the development of analytical technologies for chiral amino acids, a large number of D-amino acids and bioactive peptides containing D-amino acids have been found in various organisms, including mammals, plants, microorganisms and humans. D-amino acids possess unique physiological activities such as neural signal transduction, hormone regulation, antibacterial effect and immune regulation. Daily diet is an important source of D-amino acids for humans, and the daily average supply of D-amino acids for humans is about 100 mg. D-amino acids in foods mainly origin from processing conditions such as fermentation, high temperature and certain pH, along with a small amount from food raw materials. At present, emerging functional foods with D-amino acids as the major component have begun to appear in the market. D-amino acids hold great potential that deserves to be explored further and are expected to be an important ingredient for the development of new functional foods in the future.