Optimization of Vacuum Freeze Drying Technology of Miscellaneous Grains Vinegar Powder by Response Surface Methodology

With bitter buckwheat powder,oat bran,black soybean skin as raw materials,the traditional Shanxi vinegar brewing process was used for brewing and smoking,after smoked,the materials were vacuum freeze-dried and crushed to prepare miscellaneous grains vinegar powder. With the drying rate and total acid content as indicators,the influencing factors of freeze-dried miscellaneous grains vinegar powder was analyzed by single factor and response surface tests,and the freeze-drying process was optimized.The results showed that the optimal freeze-drying conditions were pre-freezing temperature-40 ℃,material thickness 9 mm,sublimation temperature 28 ℃,analytical temperature 33 ℃. At this time,the miscellaneous grains vinegar powder drying rate of 3.60%/h,the total acid content of 8.53 g/100 g.This study provided a theoretical basis for industrial production of the miscellaneous grains vinegar powder.