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Storage systems with controlled environment Storing in controlled atmosphere (environment) is a technology that helps to increase the products lifetime significantly and preserve their quality. The key point of the technology is creating environment for storage that has specific characteristics, based on:
- temperature mode for storage;
- relative air humidity;
- specific air composition including the content of oxygen and carbon dioxide.
Fruits placed to a closed environment due to their natural respiration process change the partial pressure of CO2 and oxygen in the surrounding air. The amount of oxygen in the air is constantly decreased, and its partial pressure also becomes lower. This slows down the respiration of fruits. The concentration of CO2 constantly grows.
In regulated environment, as opposite to an ordinary environment, the quality of fruits and vegetable is preserved better. CO2 and oxygen also influence on ethylene biosynthesis and its biologic action on maturing processes.
Lowing the concentration of oxygen for storing fruits and vegetables influences on the following factors:
- slowdown of respiratory activity;
- decreasing of oxygenation;
- slowing maturation;
- increasing the expiry time;
- inhibiting chlorophyll dissociation;
- decrease of ethylene synthesis;
Controlled environment chambers must provide higher gas proofness. This is achieved by applying special materials for constructing and processing the camera surfaces, installing the airproof doors of special configuration.
 To create proper gas environment for storing fruits and vegetables in controlled environment the specialists use these technologies:
-RCA (Rapid Controlled Atmosphere) – the technology of quick decrease of oxygen concentration. -ILOS (Initial Low Oxygen Stress) – super quick lowering the level of oxygen in a camera. -LECA (Low Ethylene Controlled Atmosphere) – the technology of lowering ethylene level in chamber. -DCA (Dynamic Controlled Atmosphere) – technology that helps to regulate the air composition dynamically. -CO2 shock treatment - the technology of shock processing by carbon dioxide with the increased CO2 concentration (up to 30%). It is required to rely on specific requirements of fruits and vegetables in terms of supporting high relative humidity in storage rooms (80-95%) when reconstructing the existing building or constructing a new warehouse with controlled atmosphere technology.
There are a few requirements for correct product storage in CA: 1. Additional equipment must be installed into a camera for its correct operation in controlled atmosphere mode and supporting the constant level of O2/CO2: safety siphon valves (more reliable than mechanical valves), plastic expansion drums, manometers, etc. 2. The excess of oxygen must be removed from the camera at the beginning of storage period nitrogen transmission. This can be done with the help of a special generator with hollow fibbers’. Using ULO technologies implies the increase of oxygen level in chamber up to 5% during 24 hours. 3. Clean the camera from carbon dioxide using special absorbers. It is also required for supporting the constantly low CO2 level; that is why at the beginning of 80-s the centralized absorbers were replaced by autonomous systems with one device for each camera. 4. Periodical control of oxygen and carbon dioxide in CA-cameras is provided by electronic systems. The atmosphere analysis can be made both by electronic portable and stationary analyzers that are connected to automated and computerized systems. These systems can manage the manufacture via a modem; in this case there is no need in constant presence of an operator in a refrigeration camera. 5. Ethylene must be removed, especially when storing kiwi, citrus cultures, pears, tropic fruits and vegetable. Catalytic converters or chemical absorbers are used for this. The first system is based on removing ethylene by a catalyst acting on a high temperature. It guarantees even decrease of gas concentration and air sterilization. The second system uses potassium permanganat with the aim of alum earth or clay that oxidize ethylene in the refrigeration chamber. It continually loses its absorbing capacity (a few months for kiwi, a few weeks for apples, pears, etc.). Of course, these two systems have different price. 6. If it is necessary to support the high level of relative humidity, add cold air steam to the refrigeration camera by using a special air moisturizer. It is very important to design the refrigeration camera properly to make it fully correspond to specific characteristics (evaporator surface, the type of coolant, difference between coolant temperature and camera temperature). All this will help to minimize the moisture diffusion.   There are a few ways to store fruits in controlled gas environment:
1. In refrigeration cameras with CGE. 2. In polymeric films. 3. In plastic containers with diffusion inserts. Storing fruits in CGE cameras is performed in temperatures of 0...+4°С and 90-95% relative air humidity. The content of CO2 and oxygen in the camera atmosphere is checked and and regulated by gas analysers that manage the automatic operation of scrubbers and diffusors. After gaining the required CO2 concentration the cameras are switched to the preset gas mode by switching the proper device (scrubbers or diffusors), the excess of CO2 is removed and oxygen is lowered to the required level. A small amount of oxygen (air) is transferred to a camera from the atmosphere. As a result of different permeability of certain gases via silicone rubber films a specific CO2, oxygen and nitrogen concentration is created inside the camera. To generate the required gas mode quickly sometimes a big amount of nitrogen is transferred inside that quickly lowers the content of oxygen to the required level. Required mixture of СО2 and oxygen in a camera is set in 3-4 weeks after camera closure. The term of refrigerated storage of different fruits and berries in different gas environment:
 PRIMEHOLOD will perform high-quality project development and installation of controlled environment storage system according to the customer’s requirements.
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