Chemical aggregation of carbonyl compounds as the core contributor to chromatic alterations in jiangxiangxing baijiu aging

To elucidate the discoloration mechanism of Jiangxiangxing Baijiu (JXXB) during aging, this study employed direct distillation or distillation after 2,4-dinitrophenylhydrazine (DNPH) derivatization to obtain distillates, which were then treated with NaOH or NaBH₄. The correlation between carbonyl compounds and color change was assessed, while the polymerization pathway was verified using known carbonyl compounds. Functional groups in colored polymers (CPs) were characterized by ultraviolet-visible (UV–Vis), Fourier-transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectroscopy. Results indicated that volatile carbonyl compounds are key precursors for discoloration, as both DNPH and NaBH₄ treatments inhibited NaOH-induced browning. Carbonyl compounds concentration and types collectively influenced the formation of CPs, with aldol condensation identified as the primary pathway for CPs formation, supported by spectral data. This study clarifies the chemical basis of JXXB discoloration, providing a theoretical foundation for optimizing aging processes and authenticating vintage JXXB.