d-Amino Acids and Cross-Linked Amino Acids in Food

Abstract This chapter covers the process-induced formation of d -amino acids and cross-linked amino acids (CLAAs) in food. The industrial processing of food and feed proteins often includes treatment in heated alkaline or acidic solutions. Such treatments lead to two major chemical changes: formation of CLAAs, such as lysinoalanine, lanthionine, or histidinoalanine, and racemization of free and protein-bound l -amino acids into their d -isomers. Both represent undesired contaminants in food particularly because they diminish the digestibility and nutritional quality of food and may exert toxic properties.