ABSTRACT
Normally freeze drying process results in the highest overall quality for a dehydrated product as a result of extremely low temperatures during drying. The low temperatures associated with freeze drying result in fewer occurrences during drying of various undesirable thermally activated reactions, and the rigid structure of the frozen product mechanically prevents shrinkage during the drying process, allowing for excellent rehydration properties. Characteristics of final products are good flavor, aroma, nutrient retention, and excellent rehydration properties. However, the process is very slow and expensive compared with other types of drying because of its energy consumption and use of expensive equipment over long periods of time. The basic setup of a simple vacuum freeze-drying system is shown. The typical freeze-dryer includes an airtight chamber, vacuum pump to obtain high vacuum in the chamber, vapor trap, and a condenser cooled by a refrigerant to desublime water back to ice. The laboratory exercise will give students practical experience with the freeze-drying process.
