Removal of turbidity in low-alcohol Chinese baijiu by coalescence separation

Chinese Baijiu has always been preferred by the majority of alcoholic drink lovers with its rich aroma. With the popularity of drinking culture and mental health, low-alcohol Baijiu has achieved increasing attention. This paper innovatively adopts the coalescence method of separating emulsion to solve the turbidity problem in the process of degrading Baijiu. Firstly, the characteristics of feasible materials for turbidity removal via coalescence were explored. Three materials with different pore size, chemical composition, and wetting behavior, namely polyether sulfone (PES), glass fiber (GF) and polyvinylidene fluoride (PVDF), were characterized. Secondly, the emulsion structure and composition of the diluted Chinese Baijiu were analyzed. Finally, the selected porous materials were conducted to separate the precipitates in the degraded Baijiu for a clear Baijiu. The results found that both PVDF with excellent affinity to esters under alcohol solution and PES with small pore size exhibited efficient turbidity removal efficiency. Furthermore, the effect of pore size ranging from 0.1 to 5 μm of the PVDF coalescing material on the turbidity removal was investigated. However, the small pore size resulted in great pressure drop and followed the screening mechanism which contributed to high energy consumption and membrane fouling issue. The large pore size PVDF materials with average pore size of 1.6–4.0 μm achieved high flux of 5.30 × 104 L/(m2·h) with 90∼100% turbidity removal for 39% alcohol content-Baijiu via coalescence. The quality after coalescence removal of turbid was good indicating the coalescence removal method is a Chinese Baijiu turbidity removal potential technology.