Single Factor Test of Vacuum Freeze Drying for Unsaturated Yunnan Small Grain Instant Coffee

With Yunnan small grain instant coffee concentrate as main raw material, liquid material of unsaturated Yunnan small grain instant coffee was prepared by "liquid nitrogen to ice cream method"．Single factor experiment design of vacuum freeze drying for unsaturated Yunnan small grain instant coffee was carried out by changing drying temperature, drying pressure and sample specific surface area, to explore effects of these three factors on drying rate and sensory evaluation during vacuum freeze drying of Yunnan small grain instant coffee．Results showed that drying temperature, drying pressure and specific surface area of sample all affected drying rate of unsaturated Yunnan small grain instant coffee during vacuum freeze drying．Drying temperature and specific surface area of sample had significant effects on drying rate of sample, and specific surface area of sample had great effects on sensory evaluation．Drying pressure has a small effect on drying rate and sensory evaluation, and effect on sensory evaluation was relatively large．This study could provide reference for vacuum freeze drying technology of unsaturated Yunnan small grain instant coffee and optimize its process．