Reducing the bitterness of angiotensin-I-converting enzyme (ACE) inhibitory peptides from soybean protein by NADES-driven Maillard reaction.

Soybean peptide (SP) exhibits significant angiotensin-I-converting enzyme inhibitory (ACEI) activity, however, its strong bitterness restricts its use in food industry. This study aimed to reduce the bitterness of SP by natural deep eutectic solvent (NADES)-driven Maillard reaction (MR). Results showed that both the mixtures of Glucose-NADES and the Glucose-Xylose-NADES formed the hydrogen bonds and shown good thermal stability analyzed by using Fourier transform infrared (FTIR), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA). Compared with Glucose-NADES, Glucose-Xylose-NADES exhibited higher reaction activity, while lower ACEI-activity and higher bitterness were observed in its Maillard reaction products (MRPs). It also indicated that NADES's excellent ability to increase umami free amino acid (FAAs) and reduce bitter FAAs during MR, were key factors in reducing bitterness. Some amino acids (Glu, Asp, Leu and Ala) were considered to have a higher contribution to change the bitterness of MRPs. This study is expected to provide a theoretical basis for preparing functional peptides with high activity and good taste.