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Three technical issues of durian freeze-drying equipment
2026-08-06
1. Question: Durian fruit pulp is high in sugar and water. How does the equipment ensure that the internal water is completely frozen without damaging the cell structure?
Answer: The key is that the refrigeration system of the equipment must have the ability to quickly cool down and precise eutectic point control. Durian fruit pulp has a high moisture content. If it freezes slowly, it will produce large ice crystals, which can puncture the cell wall and cause rehydration in the later stage, resulting in a woody texture. Therefore, the equipment needs to be equipped with an efficient freezing system to quickly cool the fruit flesh to below -40 ℃ to -45 ℃ within 30 minutes (at least 5 ℃ below its eutectic point), ensuring that the internal moisture instantly crystallizes into extremely small ice crystals, thus perfectly locking in the shape and nutrition of durian.
2. Question: How to prevent durian from collapsing or caramelizing due to high sugar content during the sublimation drying stage?
Answer: The core lies in the precise coordination between the vacuum system and the temperature control system. The equipment needs to establish and maintain a stable high vacuum environment (usually controlled at 10-50 Pa) in the drying chamber, allowing ice crystals to sublime directly into water vapor without passing through the liquid state. At the same time, the heating temperature of the shelf must be strictly controlled, usually gradually rising from -30 ℃ to around 30 ℃ in a stepwise manner. It is absolutely necessary to avoid heating up too quickly or too high, otherwise it can easily lead to caramelization or Maillard reaction of high sugar durian flesh, affecting color and flavor.
3. Question: How to efficiently handle the large amount of water vapor generated by sublimation to ensure the vacuum level inside the drying chamber?
Answer: This highly depends on the ice capture capability of the equipment's cold trap (water trap). During the sublimation process, if the water vapor escaping from the durian flesh is not extracted in time, it will cause an increase in air pressure inside the warehouse, resulting in a stagnation of sublimation. Therefore, the freeze dryer must be equipped with a powerful cold trap system, and its temperature usually needs to be controlled at -55 ℃ or lower to form an extremely low temperature "strong water trap", which quickly recondenses the escaping water vapor into frost and firmly adsorbs it, thereby ensuring a continuous and stable vacuum environment in the drying chamber.
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