Differential modulation of aroma profiles in instant Oolong tea powder by two Aspergillus niger β-glucosidases

Tea aroma is largely shaped by volatile compounds released from glycosidic aroma precursors. This study investigated the effects of two Aspergillus niger β-glucosidases, An-G3987 and An-G8816, on modulating the aroma profile of instant Oolong tea powder. Quantitative descriptive analysis (QDA), gas chromatography-mass spectrometry (GC-MS), and odor activity value (OAV) assessments revealed that An-G3987 significantly enhanced floral, sweet, and grassy aromas by releasing key volatile compounds such as benzyl alcohol, (Z)-3-hexen-1-ol, and 1-hexanol. In contrast, An-G8816 generated a broader spectrum of volatile compounds but had a less pronounced impact on overall aroma enhancement. Kinetic studies and molecular docking analyses demonstrated that An-G3987, compared to An-G8816, exhibited higher catalytic efficiency and stronger binding affinity for typical glycosidic aroma precursors, driven by hydrogen bonding networks (e.g., Arg107/Tyr254) and hydrophobic interactions (e.g., Pro428/Tyr497). These findings indicate that An-G3987 is better suited for targeted aroma intensification, while An-G8816 may be preferable for balanced flavor modulation.