3. Drying rate and drying energy consumption of IQF Fre […]
3. Drying rate and drying energy consumption of IQF Freezing
The drying rate and energy consumption determine the cost of applying vacuum IQF Freezing technology in food. Under normal circumstances, the drying rate of materials is directly related to energy consumption. The faster the drying rate, the shorter the time and the lower the energy consumption. The problem of high energy consumption is still the bottleneck problem of the application of vacuum freeze-drying technology in food. At present, there are mainly the following methods for improving the drying rate of food and reducing the energy consumption through the process optimization method.
3.1, control the appropriate pre-freezing speed
Pre-freezing of food raw materials is a prerequisite for the freeze-drying process. Studies have shown that rapid pre-freezing and slow pre-freezing have a significant effect on the freeze-drying time required for food materials. Fast pre-freezing is required for slow pre-freezing. The lyophilization time is long. This is because the ice crystals produced during the rapid pre-freezing of the food are small, and the dense ice crystals hinder the sublimation of the ice. In the slow pre-freezing, the ice crystals formed in the food are large, and the ice crystals are relatively large. Large gaps can promote ice sublimation, but the larger the ice crystals, the greater the impact on the quality of freeze-dried products. Especially when some biological products are lyophilized, the large ice crystals produced by slow pre-freezing will break the cell structure. Product requirements are not high, you can consider increasing the freeze-drying rate by slow pre-freezing.
3.2, adjust the concentration of liquid food or change the shape of solid food
For IQF Freezing of liquid foods, it is necessary to fully consider the concentration of the solution. If the concentration is too high, it is not conducive to the sublimation of water. If the concentration is too low, although it is good for sublimation, it will waste time due to the high water content. Zhu Hong demonstrated that the collagen membrane was simple and stable when the concentration was 1g/60mL. Wang Xu et al studied the IQF Freezing process of jujube pulp. The results showed that the concentration of jujube pulp was 20%. When using IQF Freezing technology to dry liquid foods, it is necessary to fully measure the relationship between energy consumption and product quality, and explore to optimize the optimal IQF Freezing concentration, thereby increasing the freeze-drying rate.