5TH INTERNATIONAL CONFERENCE ON ADVANCES IN MECHANICAL ENGINEERING , İstanbul, Turkey, 17 - 19 December 2019, pp.1362-1363
Drying is a separation process that can be defined as the removal of water from a solid material. This process
is used as a protection method of foods since ancient times because microorganisms that cause decay of foods do not
grow or multiply without water. If the water content in food drops approximately below 10%, microorganisms can't
work. At the same time, water content should usually drop below 5% in order to protect the taste, smell and
substantiality. Like microorganisms, also, enzymes that cause chemical changes in foods do not perform without water.
Because of these reasons, dried foods can be stored for a long time. In the literature, several methods used for drying
of foods such as hot-air drying, freeze-drying, microwave drying, sun drying, etc. Freeze-drying in food is a relatively
expensive drying method since the drying speed is very low compared to other drying methods and requires high
energy usage. However, when compared with other drying methods, the highest quality product is obtained in freezedrying. In this study, drying methods are theoretically investigated and summarized. Freeze-drying was compared with
the other drying methods in terms of the quality of foods that dried with different methods, advantages, and
disadvantages of drying processes and the costs of these methods. In light of these comparisons, optimum operating
conditions were determined for freeze-drying of foods.
Keywords: Drying, Freeze-Drying