I. Overview of freeze-drying technology:

Freeze drying technology is a method of using dry air with low moisture content to separate moisture in raw materials, which is a great step forward in low-temperature drying technology from 15oC -75oC. Before entering the drying chamber, air needs to pass through the indoor unit to lower its temperature to the dew point. In this chamber, its moisture is separated out as a liquid, and the air is dried to the setting demanded value. This dry air will separate moisture in the material to be dried. The logical reason for this process is due to the difference in the moisture that contents between the material and the drying agent.

Almost all cold-dried products have a little change in quality, taste, and appearance after drying. Especially for fruits and vegetables that contain many vitamins, and need high requirements on color and appearance, the application of freeze-drying technology is the most optimal solution in comparison to the one of heating by hot air which is easy to change color, shrink, and reduced vitamin content. This is a great advantage that cool drying technology could perform.

Moisture in freeze-dried products is very low, only 5-18%, which could restrict the growth of microorganisms, increasing the shelf life of the product up to 1 year at room temperature without changing the quality of the product.

II. Market demand

Freeze-drying technology has been researched and produced by developed countries for a long time. Products applying freeze-dried technology such as dried mango, dried avocado, dried lychee, dried vegetable, and tuber powder, and freeze-dried cordyceps are quite popular and famous in the current market.

Vietnam is an agricultural country with abundant food materials such as agricultural products: fruits, vegetables, pharmaceuticals, etc. Learning, technology transferring, and application of freeze-drying technology in production and processing have enhanced the value of Vietnamese food and agricultural products to a new level that could meet the needs of exporting to international markets and at the same time bring high profits for domestic enterprises.

Grasping the quality requirements and high demand of the market, VTStek has researched and successfully applied freeze-drying technology for food processing, especially for agricultural products, fruits, and vegetables.

In recent times, freeze-drying technology was not applied much because foreign products were very expensive, so few Vietnamese manufacturers could invest. The technology has been perfected, VTStek engineers have completely mastered the design, manufacturing, and processing technology, and the price becomes reasonable therefore, freeze dryers are increasingly being used to replace heat dryers.

Freeze dryer has contributed to the prestige of the VTStek brand, being the number 1 choice of customers due to its reasonable price, outstanding advantages, quality, and modern technology meeting food hygiene and safety standards. 

3. Operating principle of food freezing technology

Freeze-dried food is operated in a cyclic, closed process. There are two stages of processes as follows:

• Stage 1: The process creates a low-temperature and dry air stream at low temperatures from 15°C - 75°C.

Air carrying high humidity from the drying chamber passes through the indoor unit to lower its temperature to the dew point. Hence, the steam will be condensed and separated from the air, the dry air will be recirculated back into the drying chamber.

Depending on the type of material, the operator can increase the drying temperature to shorten the drying time without affecting the product quality. 

• Stage 2: Product drying process

The dry air stream is distributed evenly throughout the drying chamber and in contact with the raw materials by the fan system. Due to the difference in humidity, the vapor in the raw materials will be separated and enter the drying agent. The humidified air is again dehumidified into dry air and continues to return to the drying chamber, repeating the process as above until the product moisture is satisfactory.

Advantages

• Creating high-quality plastic dried fruit products; keeping the color and nutrition of raw materials (nutrients in agricultural products are easily denatured at high temperatures).
• Materials in contact with products meet food safety and hygiene standards.
• No dust, independent of weather because the device is completely sealed, does not affect the environment, humidity ...
• No toxic fumes such as drying with fuel, no environmental pollution, no noise pollution.
• Reduces water activity in the product to help preserve it longer.
• Flexible application depending on investment scale.
• Easy to use and operate.
• Save energy and costs.

Application

Freeze-drying technology has been researched and produced by developed countries for a long time. Products that apply freeze-dried technology such as dried mango, dried avocado, dried lychee, dried vegetables, freeze-dried vegetable powder, and freeze-dried cordyceps... are quite popular, and well-known in the market today.