Analysis of Maillard reaction products
Analysis of Furosine
A clear marker of early Maillard reactions is the compound furosine: ε-N-2-(furoylmethyl-L-lysine, formed by acid hydrolysis of an Amadori product and therefore serves as a suitable marker of process and food quality.
However during amino acid analysis, when acid hydrolysis is applied to determine the available lysine content, the Amadori product is partially reverted to lysine, meaning: the value found after acid hydrolysis as performed in a regular analysis does not necessarily reflect the total amount of available lysine.
The terms “available lysine”, “total lysine” and “reactive lysine” however, often lead to misunderstanding. Reactive lysine refers to lysine residues that haven’t undergone any Maillard reaction and can therefore be considered as “available lysine”, meaning it can be adsorbed and utilized in protein synthesis. Total lysine refers to reactive lysine + blocked lysine together.