What is freeze drying? Advantages, disadvantages and applications

1Learn about freeze drying technology

1.1 What is freeze drying?

Freeze drying (also known as freeze drying) is the process of removing water from food, helping the water to change from solid to gas in a vacuum environment. In vacuum conditions, when water sublimates directly, it will change from solid to gas. Thanks to that, the product after drying still retains the shape, taste, color as well as nutrients in the food.

1.2 What is freeze-drying food for?

The purpose of freeze-drying is to preserve the biological and chemical structure of food through the sublimation process. Therefore, food after freeze-drying can be preserved for a long time without the need for any other chemical preservatives.

In addition, thanks to this modern drying method, food can retain its full flavor, color and nutrients effectively. Therefore, freeze-dried food is very popular on the market, especially in countries with many natural disasters.

Freeze drying technology

2Food freeze drying process

  • Fresh food is flash frozen at temperatures from -30°C to -50°C and placed in a vacuum chamber.
  • In a vacuum environment, the ice part of the food will sublimate without going through the liquefaction stage (about 90% of the moisture in the product is removed).
  • Next, move to the secondary drying stage to sublimate the remaining moisture. The temperature is gradually increased to > 0 degrees Celsius. At that time, the moisture content in the product will be about 1 - 4%.
  • At the end of the freeze-drying process, the food is vacuum-packed to prevent moisture from entering and causing oxidation.
  • Soak freeze-dried food in water during processing to return the ingredients to their original state with full flavor and nutritional content.
Công nghệ sấy thăng hoa hiện đại ứng dụng trong ngành thực phẩm

Modern freeze drying technology applied in the food industry

3Stages of Freeze Drying

The freeze drying stages vary from one production unit to another, but there are three stages that must be passed through when performing the process. These include:

3.1 Freezing stage

This is the stage that largely determines the quality of freeze-dried products. Food needs to be cooled to at least the melting point of that food. If it is not completely frozen or at the required level, the food will not be of good quality after drying.

Depending on the food being dried, the manufacturer will adjust the temperature and freeze-drying time accordingly. Food needs to be frozen quickly, otherwise the ice crystals will grow large, causing the food cell walls to break and spoil the food sample.

3.2 Primary drying stage

After the freeze dryer and vacuum pump are started, the primary stage begins. The food will be cooled and evaporated in the drying chamber at low pressure. The dryer will also continuously supply energy in the form of heat to accelerate the freeze drying process.

The primary stage can last for several days depending on the type of food and the input temperature. After completion, about 93% of the water in the food will be released and enter the secondary drying stage to increase the preservation time.

Thực phẩm được đặt vào buồng máy tiến hành sấy thăng hoa

Food is placed in the machine chamber to be freeze-dried.

3.3 Secondary drying stage

At this stage, heat is added to almost completely remove excess moisture, leaving only about 2% of the food. This maximum dehumidification allows food to be preserved and kept longer without worrying about spoilage.

Freeze dried yogurt

4Advantages and disadvantages of freeze drying

4.1 Advantages

  • The dried product retains its original state: Freeze drying retains the biological and chemical structure of the food, thereby not losing its flavor, color, shape or nutrients.
  • The dried product has the ideal crispness: Freeze drying has removed water as well as moisture in the food, so when eaten it will feel crispy and chewy without being dry or too soft.
  • Not picky about food: Freeze-drying technology can be used for many types of food including succulent foods, foods rich in essential oils, large meat and fish,...

4.2 Disadvantages

  • Relatively high price: Using modern technology and machinery, the cost of freeze-dried food is quite high but worth it.
  • The time to complete a drying batch is relatively long: To ensure the quality of the finished product after drying, it requires a lot of time and effort to make a standard drying batch.
  • Maintenance costs and materials used for maintenance are quite expensive: When modern machinery and equipment have problems, it will cost a large amount of money to repair them, as well as using very expensive lubricants.

5Application of freeze-drying technology in food production

Nowadays, the application of freeze-drying technology in food is very popular.

  • Freeze-drying medicinal herbs: Natural medicinal herbs such as cordyceps, lingzhi mushrooms, etc. are often easily transformed and lose their properties, so people will directly apply freeze-drying technology during the production process to preserve them.
  • Preserve and freeze-dry juicy foods such as vegetables, kiwi, strawberries, oranges, lemons, watermelon, mango, jackfruit,...
  • Foods in powder form: Vegetable powder, meat and fish powder, cocoa powder, etc.
  • Fresh ingredients such as seafood, meat,...
  • Dried yogurt that kids love is also a freeze-dried food.

Freeze-dried jackfruit with original flavor

Where to buy quality dried and freeze-dried foods?

Foods that apply freeze-drying technology such as jackfruit, durian, mango, yogurt... are being sold at  An Khang Foods . You can order at  Shopee booth  or through  our website.

 

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