Evaporation of biological materials

Long-tube vertical evaporator. Condensed milk. 

Agitated-film (wiped-film) evaporator. Rubber latex, gelatin, antibiotics, fruit juices. 

Heat-pump cycle evaporator. Fruit juices, milk, pharmaceuticals. 

To reduce this tendency to stick and to reduce residence time, high rates of circulation over the heat-transfer surface are necessary. Since the material is heat-sensitive, low-temperature operation is also necessary. Hence, a fruit juice concentration plant usually employs a single and not a multiple evaporation unit. Vacuum is used to reduce the temperature of evaporation. 

A typical fruit juice evaporation system using the heat pump cycle is shown (PI, Cl), which uses low-temperature ammonia as the heating fluid. A frozen concentrated citrus juice process is described by Charm (Cl). The process uses a multistage falling-film evaporator. A major fault of concentrated orange juice is a flat flavor due to the loss of volatile constituents during evaporation. To overcome this, a portion of the fresh pulpy juice bypasses the evaporation cycle and is blended with the evaporated concentrate. 

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