Elucidating the aging mechanism of Fuyu-flavor Baijiu mediated by metal ions via GC–MS, spectroscopy, electrochemistry, and SEM-EDS

Metal ions can promote the aging of Baijiu and improve its sensory quality. However, the aging mechanism mediated by metal ions remains unclear. The content of esters, alcohols, and pH decreased while the acids content, viscosity, and conductivity increased after adding metal ions. 20 kinds of aroma components were identified in Baijiu including esters, acids, alcohols, and aldehydes by Gas chromatography-mass spectrometry (GC–MS). Spectroscopy and electrochemical analysis demonstrated that Fe 3+ has a higher affinity than Cu 2+ for the flavor compounds, and both Fe 3+ and Cu 2+ exhibit stronger affinity with acids than corresponding esters. Scanning Electron Microscope (SEM) demonstratesd that Baijiu can form lamellar, spherical, flower-like, and crystal-like morphology during aging. The colloidal particles exhibit different elemental composition according to Energy Dispersive Spectrometer (EDS). These results indicated Baijiu aging is regulated by transition metal ions, thereby providing a theoretical foundation for Baijiu aging by selecting appropriate aging medium and storage conditions.