Pet Food Frozen Dryer

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Analysis of Factors Affecting the Speed of Food Frozen Dryer

The whole process of freeze-drying is actually a process in which heat and mass transfer (water vapor) are carried out at the same time. The heat and mass transfer rate jointly affect the drying rate, thus affecting the whole freeze-drying cycle. All factors affecting heat and mass transfer will affect the drying rate. To sum up, the main factors affecting heat and mass transfer are: 

01.Form and composition of materials

According to the form of freeze-dried materials, they are usually divided into solid and liquid. The shape of solid and the concentration of liquid have a great influence on the freeze-drying rate.

02.Pre-freezing rate

The crystal size formed during freezing greatly affects the drying rate and the dissolution rate of dried products. There are the following differences between quick freezing and slow freezing: the ice crystals produced by quick freezing are smaller and those produced by slow freezing are larger. Large ice crystals are conducive to sublimation, while small ice crystals are not conducive to sublimation. Rapid freezing leads to low sublimation rate and fast desorption rate; Slow freezing leads to fast sublimation rate and slow resolution rate.

03.Loading capacity

When materials are freeze-dried, there is a certain ratio between surface area and material thickness after sub loading into containers, that is, freeze-drying is related to loading capacity. Small surface area and thickness are conducive to moisture sublimation, easy freeze-drying and ideal quality. During drying, the dry wet weight loading on the material tray per unit area is an important factor determining the drying time. Generally, the thinner the material stacking thickness, the faster the heat and mass transfer speed, and the shorter the drying time. However, if the material thickness is thin, there are less materials dried in each batch per unit freeze-drying area, which is unfavorable to improving the output per unit freeze-drying area and unit time.

04.Pressure in drying chamber

The pressure in the drying chamber affects the rate of heat and mass transfer. In terms of mass transfer, the lower the pressure, the better, while in terms of heat transfer, the higher the pressure, the better. The mass transfer rate is mainly determined by the temperature and pressure of the sublimation interface and the surface of the drying layer. To improve the escape rate of water vapor in the drying layer, first, increase the temperature of the sublimation interface and increase the water vapor pressure at the interface; The second is to improve the vacuum degree of the drying chamber and reduce the steam pressure on the surface of the drying layer.

05.Heat transfer mode

According to the traditional classification, it can be divided into conduction, convection, thermal radiation and medium heating (microwave heating). Because the sublimation drying process involves the transfer of heat and mass (water vapor), the way of heat transfer to transfer heat to materials more effectively has a great impact on the drying rate.

Introduction to the Four Major Systems of Pet Food Frozen Dryer

Pet Food Frozen Dryer are high-tech appliances commonly used in the food industry to preserve various perishable products such as fruits, vegetables, meats, and dairy. These machines rely on four major systems to produce freeze-dried food products: 

Refrigeration system

This system is responsible for cooling and freezing the food products to temperatures below their freezing point. It consists of a compressor, condenser, evaporator, and expansion valve, and works by circulating a refrigerant gas through the system to absorb heat and transfer it outside the dryer.

Vacuum system

This system is responsible for creating a vacuum inside the dryer chamber, which helps remove the moisture from the frozen food products. It consists of a vacuum pump, vacuum gauge, and vacuum valve, and works by removing the air from the dryer chamber to create a low-pressure environment, which facilitates the sublimation of water molecules.

Heating system

This system is responsible for providing heat to the frozen food products inside the dryer chamber, which helps sublimate the water molecules and turn them into vapor. It consists of heating elements or a hot gas inlet, and works by providing a controlled amount of heat to the frozen food products to facilitate the sublimation process.

Control system

This system is responsible for controlling and monitoring the entire freeze-drying process, including temperature, pressure, and moisture levels inside the dryer chamber. It consists of a microprocessor-based controller, sensors, and displays, and works by gathering data from various sensors and adjusting the operation of the other three systems to achieve the desired outcome.

Freeze Drying Process of Pet Food Freeze Dryer

The freeze drying process of pet food freeze dryer involves several distinct steps.

Pre-treatment
This step involves cleaning and rendering the pet food to remove any dirt, grease, or impurities. It also involves conditioning and adding any preservatives, colorings, or flavorings, as needed.
Freezing
The food is then quickly frozen to around -30°c to -80°c to preserve the food's structure, texture, and nutritional content.
Freezing vacuum
The food is moved to a freeze dryer which removes the moisture by creating a powerful vacuum inside the chamber. The food is exposed to low vacuum, sublimation, and a high-intensity heat source. This vacuum drew moisture out of the food, which is then collected as vapor and stored in a collection tank.
Final drying
This step takes place in the freeze dryer and involves increasing the temperature and vacuum to remove the last traces of moisture.
Packing
The freeze dried food is then packed in either hard vacuum packs or foil pouches which then seals the food. This helps prolong the shelf life and ensures the food stays fresh and tasty.