The Impact of Freeze Drying on Bioactivity and Physical Properties of Food Products

Freeze drying (FD) is a technique used to preserve the bioactive content and flavor of samples. Foods with a short shelf life due to nature have been preserved by FD in recent years. The success of the drying technique is thanks to the high retention ability of the bioactive compounds and the flavor of the sample. However, the high cost and energy consumption of the FD limit its usage in several fields. Freezing, primary drying, and secondary drying, which take place in the same device, are the stages of the FD. In addition, several parameters, including pretreatment, size, temperature, sample species, time, and pressure, affect the FD process. These parameters are controlled to increase the effectiveness of the FD on the samples. Moreover, FD was compared with other drying techniques including hot-air drying, microwave drying, vacuum drying, and solar drying to determine its protective capability. It has also been applied to the valorization of waste products, which is a common problem worldwide. For valorization, microencapsulation and powder production have been achieved by FD. In recent years, studies on the effects and use of the FD on various materials increased, providing new aspects for the future of science and food industry.