The impact of the freeze-drying process of the pilot freeze-drying machine on the nutritional content of food is mainly reflected in the following aspects:

1. Protein

During the freeze-drying process, the degree of protein denaturation is relatively low because the entire process takes place at low temperatures, resulting in minimal structural damage to the protein. Research has shown that the retention rate of proteins during freeze-drying can reach over 90%. In addition, the amino acid composition of proteins does not change significantly during the freeze-drying process, which is beneficial for maintaining the nutritional value of food.

2. Fat

During the freeze-drying process, fat is affected by low temperature and low pressure, which weakens the intermolecular interactions and facilitates the crystallization of fat, with a retention rate of over 90%. However, the degree of fat oxidation is related to the freeze-drying temperature, rate, and type of fat, and unsaturated fatty acids are more prone to oxidation than saturated fatty acids. Adding antioxidants such as vitamin E can significantly reduce the degree of fat oxidation.

3. Vitamins

During the freeze-drying process, the stability of vitamins is influenced by various factors such as temperature, humidity, and light. Research has shown that the retention rate of water-soluble vitamins (such as vitamin C and B vitamins) during freeze-drying is relatively high, with an average reduction of about 10% -20%. Fat soluble vitamins (such as vitamin A and E) undergo reduced oxidation in a vacuum environment, and their retention is also good. By optimizing the freeze-drying process parameters, such as reducing temperature and shortening time, the retention rate of vitamins can be further improved.

4. Minerals

Minerals have a short heating time, low temperature, and minimal structural damage during the freeze-drying process, with a retention rate of over 90%. The removal of water during the freeze-drying process will result in a relative increase in mineral concentration, further enhancing its nutritional value.

5. Carbohydrates

During the freeze-drying process, the retention rate of carbohydrates is relatively high, reaching over 95%. Low temperature and low pressure conditions are conducive to the crystallization of carbohydrates, and have little effect on the structure of carbohydrates, which can maintain the taste and nutritional value of food.

6. Antioxidant substances

Antioxidants (such as polyphenols and flavonoids) are protected by low temperature and vacuum environment during freeze-drying, resulting in less oxidation loss and helping to maintain the natural antioxidant properties of food. Adding antioxidants or using special packaging techniques can further enhance the antioxidant capacity of freeze-dried foods.

7. Microbial contamination

The freeze-drying process can effectively kill microorganisms such as bacteria, mold, and yeast in food, reducing the risk of microbial contamination in food. The microbial indicators of freeze-dried food are usually superior to other dried foods, which helps to extend the shelf life.

8. Water activity

Freeze dried foods have a low water activity (usually below 0.6), which is beneficial for inhibiting microbial growth and enzyme activity, thereby maintaining nutrient stability. During the low-temperature freeze-drying process, the decrease in water activity helps to reduce the degradation of vitamins and antioxidants.

Measures to improve nutrient retention rate

Optimize freeze-drying process parameters: Control the freeze-drying temperature (recommended below -40 ℃) and pressure (below 0.05MPa) to improve the retention rate of nutrients.

Improving packaging: Using oxygen blocking, light blocking, and moisture blocking packaging materials to reduce the contact between food and the external environment and minimize the loss of nutrients.

Adding stabilizers: Adding antioxidants, preservatives, and other stabilizers to food to inhibit microbial growth and nutrient degradation.

In summary, the freeze-drying process of the pilot scale freeze-drying machine has significant advantages in preserving the nutritional components of food, especially in terms of protein, fat, vitamins, and minerals. By optimizing the freeze-drying process and packaging technology, the retention rate of nutrients can be further improved, providing consumers with higher quality food.