What Is Controlled Atmosphere Storage? A Complete Guide to Controlled Atmosphere (CA) Stores

Even when picked, fruits and vegetables still respire, absorbing oxygen while giving off carbon dioxide, water vapor, and heat as well as changing texture and losing freshness. The use of standard cold storage is one way of slowing down this process due to bringing down temperature; however, the system disregards the production of gases occurring at room temperature. Controlled atmosphere (CA) stores do the additional part by actually adjusting the levels of gases like oxygen, carbon dioxide, and nitrogen in the sealed store to decrease the rate of respiration. It is important for growers, exporters, and cold chain operators to have a clear understanding of how CA storage functions and how the technology should be implemented in conjunction with traditional refrigeration methods.

What Is Controlled Atmosphere Storage?

Controlled atmosphere storage is a post-harvest preservation technology designed to keep fresh food inside a sealed room where the levels of oxygen, carbon dioxide, temperature, and humidity are controlled. A controlled atmosphere (CA) storage keeps the level of oxygen lower and the level of carbon dioxide higher in the room, thus reducing the respiration rate of fruits and vegetables and allowing for a longer shelf life compared to cold storage alone.

There is no unique method of Controlled Atmosphere (CA) storage applicable to all commodities. The required levels of gases, temperature, and time for CA storage differ based on the variety of produce and its maturity at the time of harvesting and for how long the produce needs to be stored. Therefore, CA storage should be tailored according to each crop.

How Does a Controlled Atmosphere (CA) Store Work?

A CA store is created to be a gas-tight storeroom, featuring insulated panels, sealed doors, and air-tight seams to prevent the entry of outside air and also to prevent the escaping of air from inside the room. Once the room has been filled to its capacity and sealed shut, several coordinated systems operate to keep the atmosphere stable.

• Oxygen reduction – While nitrogen is usually produced in situ, its effect is as the oxygen level drops below the usual ambient quantity, thus inhibiting respiration and maturation.
• Carbon dioxide management – The amount of CO₂ produced by the fruit is carefully measured and eliminated whenever needed, because too high CO₂ levels can lead to many quality issues as well.
• Temperature control – The cooling unit works to maintain the required temperature in the room and complements the operation of the environment instead of raising it.
• Humidity management – The humidity levels are controlled so that moisture is retained without allowing condensation or deterioration to take place.
• Atmospheric monitoring – Gas detectors constantly monitor oxygen, carbon dioxide, temperature and humidity parameters. These measurements are registered by an automatic system which alters the rate of nitrogen injection and CO₂ removal.

It is that combination that makes this method more effective in slowing down the advance of produce's biological clock than temperature by itself.

Controlled Atmosphere Storage vs Conventional Cold Storage

While traditional cooling and controlled atmosphere (CA) storage use refrigeration, their approaches differ in the level of control over the produce's surroundings.

In short, conventional cold storage manages temperature; a controlled atmosphere cold storage facility manages temperature, humidity, and the composition of the air itself.

Why Are Oxygen and Carbon Dioxide Controlled?

Respiration is a major biological process that brings about the majority of the decline in quality after harvesting. The process of respiration refers to the uptake of oxygen and release of carbon dioxide while converting stored carbohydrates into usable energy. This is a process that finally leads to over-ripening, softening, and rotting. Therefore, reducing the amount of oxygen present reduces respiration rate in a drastic way and also minimizes the activity of ethylene, the natural ripening hormone produced by most fruits.

Carbon dioxide is effective too but when it comes to slowing the ripening process, one must not allow CO₂ to become too high because of the risk of inducing internal browning, off-flavors or fermentation of some commodities and products. This is the reason why in Controlled Atmosphere technology, it is important to maintain a balanced composition of oxygen, rather than reducing its amount as much as possible to a minimum.

What Products Can Be Stored in a CA Store?

Controlled atmosphere (CA) storage is most commonly used for crops that have a natural predisposition to long storage and a slower ripening process, which includes some sorts of apples and pears, kiwifruit, and certain varieties of cabbage. CA method can also be used in other agricultural crops that prove to be worth the expenditure of more money, thus allowing their longer freshness and quality.

However, not all fruits and vegetables tolerate low oxygen levels. Some are susceptible to injuries caused by cold storage and physiological disorders in CA; produce with low respiration may even get by without CA. Suitability is based on the particular crop, the maturity, and the period of storage, so the product is chosen case by case.

What Are the Benefits of Controlled Atmosphere Cold Storage?

• Enables an increased shelf life, extended beyond traditional refrigerated stocking of appropriate products
• Helps minimize post-harvest losses through the supply chain
• Preserves produce quality — firmness, colour, and flavour — over longer storage periods
• Allows for a staggered release into the marketplaces (instead of selling immediately after harvesting)
• Has longer transit times, allowing for greater ease for exports
• Helps to alleviate pressure stemming from seasonal surplus of crops by providing products throughout the entire year

What Role Do Temperature and Humidity Play?

Controlled Atmosphere (CA) storage should not be considered a substitute for refrigeration. The principles of temperature and humidity control are crucial in the overall storage of fruits and vegetables, regardless of whether any type of CA storage is utilized.

Temperature control slows down enzyme activity and bacterial development, while humidity control prevents products from drying out and shrivelling without causing condensation that leads to mould. Both factors need to be controlled properly in order to achieve the results intended by CA storage.

How Does CA Storage Support Agri-Exports?

The lifespan of agri-export cold storage is often correlated with the distance and duration of crops that successfully reach their destination in pristine shape. Controlled atmosphere (CA) storage significantly helps to increase this time frame, allowing the exporter to choose new shipping routes, transport modes, and sale markets that would otherwise not be suitable for fresh produce.

Thus, the advent of CA storage has proven to be crucial in terms of cold chain logistics since it makes it possible to bridge the gap between the harvest and the sale regardless of the shipping mode used. In particular, for maritime shipments, CA storage contributes to keeping the harvest fresh for the duration of the long transit period.

What Equipment Is Used in a Controlled Atmosphere Warehouse?

A controlled atmosphere warehouse that is in working condition usually includes several components such as gas-proof structures, doors and seals, air conditioning systems that are proper for the amount of work, machines that help produce nitrogen to minimize the level of oxygen, carbon dioxide scrubbers, devices for surveying gas levels (oxygen, carbon dioxide, temperature and humidity), automatic systems for gathering information from sensors and controlling the room conditions, devices for controlling the humidity, and safety devices for evacuation.

If you're specifying airtight doors for a gas-tight build, our Doors & CA Doors page covers door types, sealing systems, and specifications for controlled atmosphere storage projects.

The whole system can work properly if all the components function without any preliminary faults because any malfunction makes the warehouse useless.

What Are the Limitations of Controlled Atmosphere Storage?

The CA storage method would not suit all types of operations because it entails a larger upfront investment than the traditional cold storage method. The process of CA also uses sophisticated monitoring equipment and the airtight construction features. CA storage facilities need constant maintenance and calibration because even a minor shift in the temperature or environment may affect the quality of the stored products.

Reduced oxygen chambers also have to be treated with respect since there are safety implications. This means that entering a room requires considering the fact that air inside it may not be breathable like air outside. Also, due to the fact that the different controlled atmosphere parameters differ depending on the type of products, you might have either several separate rooms or a careful schedule to maintain different controlled atmospheres.

How to Choose the Right CA Storage System

The appropriate system is determined by what is to be loaded, and for how long and how much. It is worth checking prior to deciding on a construction: what commodities the installation serves, what is the duration of loading and what throughput is going to be required, if the buildings are essentially gas tight rather than insulated well, and what the accuracy of the atmospheric monitoring and control system is.

Working through these issues with a professional cold storage solutions provider when a construction has not yet started helps to avoid retrofitting a facility without atmospheric control.

Frequently Asked Questions About Controlled Atmosphere Storage

What is a controlled atmosphere (CA) store?

An airtight facility in which the levels of oxygen and carbon dioxide are effectively controlled as well as the temperature and humidity, resulting in decelerated respiration of produce and longer shelf life.

What is the difference between CA storage and conventional cold storage?

Cold storage is only concerned about temperature and humidity to a certain point. On the other hand, CA storage controls the oxygen and carbon dioxide levels in a gas-tight room, allowing for an adequate management of the ripening process.

What gases are controlled in CA storage?

The main gases present in CA storage are oxygen and carbon dioxide with nitrogen being used for the purpose of substitution. Also, some systems monitor the level of ethylene, since it is known to play an important role in the process of ripening of certain fruits.

Is controlled atmosphere storage suitable for vegetables, or only fruit?

Both of these crop storage methods apply to certain crops depending on the type. Controlled atmosphere storage is effective for certain long-storing fruits. Some other vegetables, such as many types of cabbage, can also use it. It depends on whether a particular commodity can be stored using a controlled atmosphere.

How long can produce stay in a CA store?

The duration of storage depends on the specific commodity, type, and level of quality. Some fruits can last for months beyond the reach of ordinary refrigeration.

Does CA storage replace the need for refrigeration?

While temperature and humidity control is necessary, the management of the atmosphere plays a complementary role to refrigeration technology.

Is CA storage useful for agricultural exports?

Indeed. By increasing the time needed for products to be stored, it enables longer transportation times and diversifies the range of export markets, thus becoming an important component of cold chain logistics for export oriented supply chains.

Conclusion

The term controlled atmosphere storage refers not only to refrigeration but also to the management of gas components, meaning the reduction in oxygen concentration, the control of CO2 concentrations, and keeping temperature and humidity under control with the goal of slowing the natural deterioration of good-quality agricultural products. A good controlled atmosphere (CA) store does not replace conventional refrigerated stores, but builds on the latter, thus allowing farmers and exporters and the cold chain operators to preserve the quality of agricultural goods for long periods of time. Since atmospheric conditions depend on the product itself, i.e., its type, sort, and ripeness, setting the store properly requires defining the particular goods that will be stored in the CA store.

Singhania Refrigeration designs, builds, and equips controlled atmosphere (CA) storage facilities — including gas-tight construction and airtight doors and seals — for clients across Delhi NCR, and can help you specify the right CA storage system for your produce. Explore our Doors & CA Doors range, or get in touch to discuss your project.