Abstract

Extrusion at 140 °C optimally improved gluten hydrolysis efficiency. • Complex protease hydrolysis yielded hydrolysates with the lowest bitterness. • Bitterness reduction associated with decreased hydrophobic and bitter amino acids. • The process combined 140°C extrusion with complex protease hydrolysis. • This enables high-value, low-bitterness utilization of gluten. This study systematically investigated the effects of alkaline protease, neutral protease, papain, complex protease, and flavourzyme on the properties of hydrolysates derived from gluten extruded at 130–160 °C to optimize enzymatic hydrolysis and reduce bitterness. The degree hydrolysis (DH), trichloroacetic acid nitrogen solubility index (TCA-NSI), sensory evaluation, electronic tongue response, and free amino acid composition were determined to identify the optimal protease. The results indicated that gluten extruded at 140 °C exhibited the highest enzymatic efficiency, with significantly higher DH and TCA-NSI compared to those extruded at other temperature groups (P < 0.05). Among the five proteases, flavourzyme yielded the highest DH (18.62%), while the neutral protease resulted in the highest TCA-NSI (46.2%). The complex protease group had the lowest bitterness value (sensory score=2.61; electronic tongue bitterness response=3.87). A free amino acid analysis revealed that the complex protease group had significantly lower contents of hydrophobic amino acids (8.10 mg/g) and bitter amino acids (10.70 mg/g), along with a higher content of sweet amino acids (5.30 mg/g) contributing to its reduced bitterness. Thus, extrusion at 140 °C combined with complex protease or neutral protease hydrolysis not only ensures high enzymatic efficiency but also improves the flavor profile of the products, thereby providing technical support for the high-value utilization of gluten.