Dendritic crystal pattern from a drying droplet: A distinctive feature of feng-flavor Baijiu

Visual evaluation techniques for Chinese Baijiu remain an active research area. We identified a novel dendritic crystal pattern formed after the droplet evaporation of Feng-flavor Baijiu. Interestingly, this pattern showed an obvious correlation with aging in Jiuhai container (storage vessels for aging) (R² = 0.904, p < 0.01), suggesting its potential as a visual quality indicator of Feng-flavor Baijiu. During droplet evaporation, the local solution preferentially reaches a supersaturated state at the three-phase contact line, initiating nucleation and crystallization that ultimately assemble into a dendritic crystal pattern with a coffee-ring structure. Further analysis revealed that the crystals are mainly composed of metal ions such as calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), and potassium (K⁺), which primarily originate from a unique aging container known as the Jiuhai container. Furthermore, we observed that trace components such as acids and esters can significantly inhibit or promote the formation of dendritic crystals, contributing to distinct dendritic crystal patterns across various quality grades (Ⅰ to Ⅴ) of Feng-flavor Baijiu samples. More interestingly, crystallization simulation experiments showed that dendritic crystal patterns formed in blended Feng-flavor Baijiu but not in other blended-flavor Baijiu samples. Consequently, the characteristic dendritic crystal patterns generated by droplet evaporation could serve as potential visual indicators for evaluating the quality of Feng-flavor Baijiu.