Isolation and identification of bitter peptides during sequential hydrolysis of wheat gluten by enzyme preparations with endo-and exo-activities

The effect of the released amount and bitterness threshold of bitter peptides on the sensory properties of different wheat gluten hydrolysates (WGHs) after hydrolysis was investigated. The results showed that the endo-activity of the enzyme promoted the release of bitter peptides, leading to enhanced bitterness intensity in WGHs. With the increase in degree of hydrolysis (DH), the bitter threshold of bitter peptides became the main reason affecting bitterness of the WGHs. Proteax exerted the strong exo-activity at the DH of 20%, which could reduce bitterness of Pro-16 hydrolysates. The reason for debittering was the reduction in the content with molecular weights (MWs) of 500-1000 Da and the decrease of surface hydrophobicity (SH) in the Pro-20 M hydrolysates, which led to the increase of the bitterness threshold of bitter peptide. Meanwhile, HPLC-MS/MS analysis demonstrated the reduced proportion of C-terminal hydrophobic amino acids (HAAs) in Pro-20 M extracts verifying the cause of debittering.