Measurements of temperatures, ice evaporation rates and residual moisture contents in freeze-drying.
The temperature measurements during freezing and freeze-drying are described, and the results obtained using thermocouples and resistance elements (Pt 100) are compared with the barometric temperature measurements (BTM). The BTM is checked with a mass spectrometer, thermoelectric instruments and an absolute capacity measuring gauge. The temperature measurements are also shown as a function of the location of the sensors in the product. The evaporating rates of ice are given as a function of operating pressure. It is shown that the residual moisture content is a function of the temperature of each product. The equilibrium vapour pressure as a function of temperature is shown as desorption isotherms. Therefore, the residual moisture content can be determined by measuring this equilibrium vapour pressure (or at least a pressure very close to the equilibrium vapour pressure).
Willemer
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Finn-Aqua, Köln, Germany.
D001688:Biological Products / Q000302:isolation & purification; D004553:Electric Conductivity; D005612:Freeze Drying / Q000295:instrumentation / Q000379:methods; D007053:Ice; D008353:Mannitol; D011312:Pressure; D012996:Solutions; D013696:Temperature; D013821:Thermometers; D014867:Water / Q000032:analysis
D001688:Biological Products; D007053:Ice; D012996:Solutions; D014867:Water; D008353:Mannitol