Controlled Atmosphere Fresh - keeping Warehouse

Controlled atmosphere fresh - keeping warehouse, also known as controlled atmosphere storage, is the most advanced method for fresh - keeping and storing fruits and vegetables nowadays. Based on cold storage, it adds gas composition adjustment.

By controlling conditions such as temperature, humidity, carbon dioxide, oxygen concentration, and ethylene concentration in the storage environment, it inhibits the respiration of fruits and vegetables, delays their metabolic processes, better maintains the freshness and marketability of fruits and vegetables, and extends the storage period and fresh - keeping period (shelf - life for sales). Generally, controlled atmosphere storage can extend the storage period by 3 - 5 times compared with ordinary cold storage. The fruits and vegetables stored in a controlled atmosphere warehouse "wake up" from a "dormant" state after being taken out of the warehouse. This can extend the fresh - keeping period (shelf - life for sales) by 21 - 28 days after being taken out of the warehouse, which is 3 - 4 times that of an ordinary cold storage.

(1) It can well maintain the original shape, color, and flavor of fruits and vegetables.
(2) The fruit firmness is higher than that of ordinary cold - stored fruits.
(3) The fruit decay rate is low, and the natural loss (water loss rate) is low.
(4) It extends the shelf - life. Due to the long - term effect of low oxygen and high carbon dioxide on fruits and vegetables, there is still a long "lag effect" or dormant period after the controlled - atmosphere state is lifted.
(5) It is suitable for long - distance transportation and export. The quality of fruits and vegetables is significantly improved, creating conditions for export and long - distance sales.
(6) Many fruits and vegetables can achieve annual supply from seasonal production, creating good social and economic benefits.

The body of a fresh - keeping controlled - atmosphere warehouse not only needs to have good insulation to reduce the impact of external heating on the storage temperature. More importantly, it must have good air - tightness to reduce or eliminate the pressure of external air on the gas components in storage, ensure the adjustment of the gas components in storage and a low fluctuation range, improve storage quality, and reduce storage costs. The body of a controlled - atmosphere warehouse is mainly composed of an air - tight layer and a heat - insulation layer. According to different building types, controlled - atmosphere warehouses can be divided into three types: pre - fabricated, brick - concrete, and jack - up. The building envelope of a controlled - atmosphere warehouse is made of color - coated polyurethane sandwich panels, which have functions such as heat - insulation, moisture - proof, and air - tightness. This type of warehouse is quickly constructed, beautiful and elegant, but the cost is a bit high. It is the most commonly used type for newly - built controlled - atmosphere warehouses at present. Both at home and abroad, controlled - atmosphere warehouses use special controlled - atmosphere doors, and the doors should have good heat - insulation and air - tightness. In addition, during long - term storage, after closing the door of the controlled - atmosphere warehouse, it is generally not allowed to open it casually to avoid gas exchange between the inside and outside of the warehouse and fluctuations in the gas composition inside the warehouse.

To facilitate understanding the storage situation of fruits and vegetables in the warehouse, an observation window should be set up. After the controlled - atmosphere warehouse is built, an air - tightness test should be carried out. The air - tightness should reach 300 Pa, and the half - pressure - drop time should not be higher than 20 - 30 minutes.