Food freeze dryer is a kind of food stabilization drying processing equipment, and its control technology in the food drying stage plays a vital role in maintaining the nutritional content, taste and preservation of food. This article will introduce the commonly used control technologies of food freeze dryers in the food drying stage, including temperature control, vacuum control, humidity control, time control and cooling control, and discuss their role and optimization methods in the food freeze-drying process. Food freeze dryer, fruit and vegetable freeze dryer, food vacuum freeze dryer, food freeze drying equipment-Shanghai Tianfeng Instrument Co., Ltd
1. Temperature control
In the freeze-drying process of food, temperature control is crucial. First of all, the pre-freezing stage requires the food to be cooled quickly and evenly to a pre-set desired low temperature. This temperature should be below the freezing point of all moisture in the food to prevent the formation of ice crystals. In the sublimation drying stage, the temperature needs to be gradually raised to an appropriate value to promote the sublimation of water vapor. At the same time, in order to prevent the food surface from over-drying and forming a hard crust, the temperature control should ensure that the temperature gradient inside the lyophilizer is evenly distributed.
2. Vacuum control
Vacuum control has a significant effect on water migration during lyophilization. The increased vacuum level results in a faster sublimation rate, which in turn reduces the lyophilization time. However, too high a vacuum degree may result in the loss of certain nutrients in food due to oxidation. Therefore, choosing the right vacuum level, balancing the sublimation rate and nutrient content retention, is the key to vacuum control.
3. Humidity control
In the lyophilization process, the humidity is controlled by adjusting the amount of water vapor entering the lyophilization chamber. Too high a humidity can cause a delay in the formation and sublimation of ice crystals, while too low a humidity can over-dry the food, causing its structure to become embrittle. Therefore, the humidity needs to be monitored and adjusted in real time to ensure a smooth lyophilization process.
Fourth, time control
Time control is also a key part of the lyophilization process. Insufficient pre-freezing time may result in food products not being completely frozen, and sublimation drying time that is too long or too short may affect the quality of the final product. Therefore, according to the type and thickness of the food, as well as the performance of the freeze dryer, a reasonable setting of the time of each stage is an important step to obtain high-quality freeze-dried food.
5. Residual air pressure control
Residual air pressure control mainly refers to the inflating or pumping of the lyophilization chamber after the end of lyophilization to maintain a relatively stable air pressure. This helps to prevent contaminants from the outside air from entering the cabin, thus maintaining the purity of the food. In addition, proper residual air pressure also helps to maintain the shape and structure of the food.
Fine adjustment of the control technology of the food freeze dryer in terms of temperature, vacuum, humidity, time and residual air pressure is the key to ensure the quality of food freeze-drying. Through these control technologies, the nutrients and taste of the food can be effectively protected, and at the same time, the freeze-dried food can be guaranteed to have good rehydration and preservation. By combining advanced sensor technology and automatic control system, the control effect of the food freeze dryer will be further improved.