A newly-processed Meicha (Ampelopsis grossedentata) via high-temperature re-roasting and Eurotium cristatum fermentation: Aroma characteristics and chemical basis

Meicha ( Ampelopsis grossedentata ) is a specialty Chinese herbal tea rich in flavonoids but lacks pleasant aromas. In this study, a novel process combining high-temperature re-roasting with mixed-culture fermentation using Eurotium cristatum produced Meicha with a distinctive composite aroma of “intense fungal-flowery, mellow-roasted, and harmonious sweet-fruity” notes, achieving optimal quality. HS-SPME/GC–MS and chemometrics identified 90 volatile compounds; high-temperature treatment introduced key aroma components such as ( 2E,4E )-2,4-octadienal and β -ionone, among which 21 compounds had odor activity values (OAV) ≥ 1. Dihydroactinidiolide reached 406.97 ng/g in the RMF sample, while β -ionone exhibited an OAV of 35,455.72 in RL1, confirming both as core aroma contributors. Molecular docking revealed that OR1A1 is the primary receptor for these odorants, with binding energies ranging from −8.0 to −4.8 kcal/mol, stabilized by hydrogen bonds with ASN155/HIS159 and hydrophobic interactions with TYR258/PHE206. This study is the first to demonstrate synergistic aroma improvement, offering a pathway for high-aroma Meicha products.