Cold rooms play an important role in industries such as food, pharmaceuticals, and floriculture. By maintaining appropriate temperatures, cold rooms can significantly extend the shelf life of stored products. However, when it comes to storing fruits, vegetables, and fresh flowers, focusing solely on temperature is not enough—the humidity level inside the cold room is also critically important. This article will explain the importance of humidity in the storage of fruits, vegetables, and fresh flowers.
Humidity Levels in Cold Room
The operation of the evaporator and the resulting dehumidification are the main factors affecting humidity levels inside a cold room.
Cold room systems use evaporators for refrigeration. When water vapor in the air comes into contact with low-temperature surfaces—such as the ceiling, wall panels, or the surface of goods—it condenses into water droplets or even forms frost or ice. This process continuously removes moisture from the air, lowering the relative humidity inside the cold room and making the air relatively dry.
In addition to the evaporator, the enclosed nature of the cold room itself intensifies the dehumidifying effect. As cold air continues to circulate and the entry of outside air is limited, the air inside the room keeps drawing moisture from the surface of the stored items, causing humidity levels to drop further.
As a result, under natural conditions, humidity levels inside cold rooms tend to be low.
Effects of Low Humidity on Fruits, Vegetables, and Fresh Flowers
When fruits, vegetables, and fresh flowers are stored in a cold room environment, the continuously decreasing humidity causes the air to become dry, which can have negative effects on these products.
Fruits and vegetables lose moisture, leading to weight loss, firmer texture, and diminished taste. For example, fruits may become shriveled, and vegetables may lose their crispness and freshness, resulting in a decline in commercial value.
Fresh flowers may wilt and dry out due to moisture loss. Their petals and leaves lose luster, and the petals become prone to falling off, which negatively affects both the appearance and quality of the flowers, reducing their commercial value.
Therefore, moderately increasing the humidity level inside a cold room is beneficial for storing fruits, vegetables, and fresh flowers. It helps reduce moisture loss and better preserve their appearance and quality.
How to Increase Humidity in a Cold Room
Using a humidifier is the most direct and effective method to raise humidity levels in cold rooms. Based on different operating principles, common types of humidifiers can be categorized as follows.
Ultrasonic Humidifier
Ultrasonic humidifiers work by using high-frequency ultrasonic vibrations to atomize water into micron-sized particles, which are then dispersed into the air by a fan.
The advantages include fine mist particles, high evaporation efficiency, low energy consumption, and relatively high control precision. However, they require high water quality and should be used with purified water or a water purification system.
Ultrasonic humidifiers are well-suited for cold rooms that require precise humidity control, such as those for fruits and vegetables, fresh flowers, and pharmaceuticals.
High-Pressure Spray Humidifier
High-pressure spray humidifiers work by pressurizing water and spraying it through fine nozzles, creating extremely fine mist droplets that evaporate into the air.
Their advantages include high humidification efficiency, wide coverage, and relatively low cost. However, regular maintenance of the high-pressure pump and nozzles is required.
High-pressure spray humidifiers are suitable for large-scale cold rooms for fruits, vegetables, and fresh flowers.
Centrifugal Humidifier
Centrifugal humidifiers work by using a high-speed rotating disk to fling water outward, forming mist droplets.
Their advantages include a simple structure, easy maintenance, and low energy consumption. However, their humidifying capacity is moderate, and the mist droplets are relatively large, making them less likely to fully evaporate.
Centrifugal humidifiers are suitable for cold rooms for fruits and vegetables, where precise humidity control is not required.
Electric Steam Humidifier
Electric steam humidifiers work by using electric heating to convert water into steam, which is then released into the air.
Their advantages include precise humidity control and no formation of puddles or frost on the floor. However, they have higher energy consumption, require significant initial investment, and need professional maintenance.
Electric steam humidifiers are suitable for low-temperature cold rooms that require strict humidity control in high-end environments.
How to Choose the Right Humidifier
How do you choose a humidifier that fits your cold rooms? This requires a comprehensive evaluation based on the specific conditions of the cold room, including its size, the type of items being stored, the storage temperature, and the required humidity control precision.
Cold Room Size
The larger the cold room, the greater the required humidification capacity, and the higher the performance demands on the humidifier.
Type of Stored Items
Different types of stored items have different humidity requirements.
Dry goods, nuts, and seeds generally do not require additional humidification; in some cases, dehumidification is even necessary.
Meat storage requires humidity levels between 60% and 70% RH. Typically, the cold room for meat does not need extra humidification, as excessive humidity can lead to microbial growth.
Fruits, vegetables, and fresh flowers require relatively high humidity levels (85%–95% RH), making ultrasonic and high-pressure spray humidifiers more suitable for these applications.
Cold Room Temperature
The lower the temperature inside the cold room, the more easily water vapor turns into frost or ice.
For cold rooms operating below freezing, electric steam humidifiers are more suitable due to their advantage of being less prone to frost formation.
For above-freezing cold rooms, a wider range of humidifier types can be considered. Depending on other requirements, ultrasonic humidifiers, high-pressure spray humidifiers, or steam humidifiers can be flexibly selected.
Humidity Control Precision
If the cold room requires high precision in humidity control, it is recommended to install a humidity sensor integrated with an automatic control system. This setup can monitor the humidity in real time, process and analyze the data, and control the humidifier accordingly—turning it on or off—to achieve accurate humidity regulation.
Conclusion
Maintaining the right humidity level is essential for preserving the quality of products stored in a cold room. Low humidity can cause moisture loss and dehydration, while excessive humidity may lead to condensation or frost
Choosing the right cold room humidifier depends on factors such as room size, temperature, target humidity, stored products, water quality, energy use, and maintenance needs. Proper sizing, installation, and humidity control help create stable storage conditions and protect product quality.
If you’d like to learn more about improving your cold room storage conditions, feel free to contact our team.
Frequently Asked Questions
Do I need a humidifier in a cold room?
Not always. A humidifier is useful when the humidity is too low for the products being stored, especially fruits, vegetables, and fresh flowers.
Can an ultrasonic humidifier be used in a cold room?
Yes. Ultrasonic humidifiers can provide fine mist and precise control, but they usually require good water quality and proper installation.
Can high humidity cause problems in a cold room?
Yes. Excessive humidity can cause condensation and may lead to frost or ice under low-temperature conditions.
Where should a humidifier be installed in a cold room?
It should be placed where moisture can mix evenly with the air without directly wetting products, walls, or equipment.
Why is humidity important for fruits, vegetables, and fresh flowers?
Proper humidity helps reduce moisture loss, wilting, weight loss, and quality deterioration during cold storage.
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About The Author
Evan Wang
I am Evan Wang, the General Manager, Marketing Director, and SEO Expert at Sunnyda Cold Room. I have over 20 years of experience in the refrigeration industry, and my expertise is in commercial refrigeration solutions.
I’d be delighted to share practical ideas about refrigeration products, project selection, export trade, SEO, and marketing.
Let’s connect!
