Effect of Mass Transfer Conditions During Baijiu Solid-State Distillation on Distillate Yields of Cyanide and Ethyl Carbamate

The solid-state distillation process of Baijiu is a crucial period for regulating the migration of cyanide and ethyl carbamate (EC) into the final product. However, balancing the unique flavor characteristics of Baijiu with the reduction and control of cyanide and EC remains a major challenge. Based on mass transfer conditions encountered in actual production, including steam pressure (0.01, 0.02, 0.03 MPa), steamer loading height (55, 70, 85 cm), and the mass fraction of auxiliary materials relative to the total mass of fermented grains (1%, 4%, 7%), the contents of cyanide and EC in the distillate of Baijiu solid-state distillation were quantitatively analyzed using GC-MS. Combined with extraction kinetic analysis, the effects of different mass transfer conditions (steam velocity, number of theoretical plates, porosity) on the distillation of these two compounds were investigated. The results showed that compared with the original production process, a proper reduction in steamer loading height achieved a decrease from 3.19 μg/kg to 0.61 μg/kg in the distillate yield of EC in the raw distillate, while an appropriate reduction in the mass fraction of auxiliary materials led to a decrease from 20.35 μg/kg to 10.46 μg/kg in cyanide distillate yield. In actual production, increasing steam pressure within a reasonable range, reducing steamer loading height, and decreasing the mass fraction of auxiliary materials were found to facilitate the reduction of EC distillation. In contrast, cyanide distillation was not significantly affected by steam pressure or steamer loading height, but a reduction in the mass fraction of auxiliary materials significantly decreased cyanide distillation. Furthermore, gas chromatography-flame ionization detection (GC-FID) was used to analyze changes in the main flavor compounds of the distillate. It was found that adjustments to steam pressure, steamer loading height, and the mass fraction of auxiliary materials exerted only minor effects on alcohols and esters among the flavor compounds, whereas their effects on acids were significantly greater than those on alcohols and esters. Considering the distillate yields of cyanide, EC, and ethanol, as well as changes in the main flavor compounds, the results indicated that reducing steamer loading height, increasing steam pressure, and decreasing the mass fraction of auxiliary materials could restrict the distillation of cyanide and EC without significantly compromising the flavor of Baijiu.