Performance Characteristics of Experimental Freeze-Drying Apparatus and a Drying Example of Beef Sample

Abstract

To study the controlling factors which affect the drying rate during freeze-drying process, the authors have constructed an experimental freeze-drying apparatus as shown in Fig, 1. The characteristics of the apparatus as well as the experimental results obtaind from beef samples are summarized as follows.
1. The changes in sample weight, drying rate, temperature distribution in the sample, heater and platen temperatures and total pressure during the freeze-drying process of beef sample were measured and shown in Fig. 8.
2. The weight measuring device, shown in Fig. 2, had the sensibility of 0.37g and an accuracy of 1/250 when the sample weight was 68.0g.
3. The surface and the bottom temperatures of the beef sample were controlled within (-35-98) ±0.4°C, (-35-85)±0.5°C, respectively.
4. During sublimation dehydration process, the sublimation front showed a minimum temperature and its values were lower in the center portion of the sample than the values near the surfaces (See Fig. 8).
5. The average moisture content of dry beef specimen, which was determined by Karl Fischer method, was 3.4% w. b. (See Table 3).