Abstract: To overcome disadvantages of freeze-drying that is usually lengthy and expensive,a novel idea,freeze-drying of initially unsaturated porous frozen material,was proposed.An experimental investigation was performed to verify the effect of unsaturated frozen materials with a certain initial porosity on freeze-drying of liquid materials.A multifunctional freeze-drying apparatus on the lab scale was designed,made and assembled.Mannitol was selected as the primary solute in the solution.Liquid nitrogen ice-cream making method was used to prepare frozen materials with different initial saturations.Results show that the unsaturated frozen material can enhance the freeze-drying process significantly and the drying time is reduced substantially compared to conventional freeze-drying for the same material quantity and initial moisture content under the same operating conditions.The drying time with the unsaturated material (initial saturation=0.28) was 36.4% shorter than that with the conventional one(initial saturation=1.00).The smaller the initial saturation is,the shorter the drying time is and the lower the moisture content of dried products is.

Key words: freeze-drying, liquid material, unsaturated, initial saturation, drying curve

摘要： 提出了“初始非饱和多孔物料冷冻干燥”的思想,从实验上验证具有一定初始孔隙的非饱和多孔物料对液体物料冷冻干燥过程的强化作用。设计、加工和组装了一套实验室规模的多功能冷冻干燥装置。采用“液氮制作冰激凌法”,将以甘露醇为主要溶质的液体物料制备成具有不同初始孔隙的冷冻物料。对于相同质量和相同湿含量的非饱和冷冻物料,在相同的操作条件下,进行冷冻干燥实验,并与常规冷冻干燥相比较。结果表明,初始非饱和物料对冷冻干燥过程确实具有显著的强化作用。非饱和冷冻物料(初始饱和度0.28)的干燥时间比常规冷冻物料(初始饱和度1.00)能够节省36.4%。初始饱和度越小,干燥时间越短,干燥产品的含水率越低。

关键词: 冷冻干燥, 液体物料, 非饱和, 初始饱和度, 干燥曲线