Vacuum freeze drying process:
Step 1: Pre-processing
Depending on the source and application of the raw materials, the pretreatment methods are also different. For example, the pretreatment of fruits is to select, clean and cut into pieces, the vegetables need to be blanched, while the instant porridges need to be cooked and plated.
Step 2: Pre-freeze
Raw materials shall be pre-frozen after pre-treatment. This is because: there is a lot of moisture inside the material, if the vacuum treatment is directly performed, the gas dissolved in the water will escape due to the reduction of the external pressure, and air bubbles will form, resulting in voids inside and on the surface of the material, which will affect the sensory quality.
Step 3: Quick frozen
In order to solidify the moisture inside the material, quick freezing is usually required. The shorter the freezing time, the faster the material freezes, the smaller the internal crystallization, and the less mechanical damage to the material cells. Therefore, the appropriate freezing speed needs to be selected according to the actual production.
Step 4: Vacuum drying
Vacuum drying is generally divided into two stages: sublimation drying and analytical drying. Sublimation drying is mainly aimed at the free water in the material; analytical drying is mainly to remove the adsorbed water with strong solid binding. The degree of vacuum, temperature and thickness of the plate during the drying process directly affect the drying process and product quality.
The advantages of food vacuum freeze dryer:
1. It can maintain the original color, aroma, taste, shape, protein and vitamin of food.
2. Natural, no preservatives, has excellent fresh-keeping ability.
3. Under the condition of good packaging, there is a very long shelf life and corresponding shelf life.
4. Can be stored at normal temperature, so complicated cold chain is not needed, namely, no cold storage / refrigerated transportation tools,
5. Warm sales containers and household refrigerators.
6. The moisture that accounts for most of the weight of the food has been removed, so it is light and easy to transport.
7. Quick rehydration quickly, easy to eat.
8. It will bring you extremely high-added value and economic benefits.