Controlled Atmosphere Systems for Transportation of Perishable Produce

Every year, millions of tonnes of fresh fruits and vegetables travel across continents – by sea, road, and rail – to reach consumers thousands of kilometres from where they were harvested. The biggest challenge? Keeping them fresh. While refrigeration has long been the backbone of cold chain logistics, it only controls temperature. Controlled atmosphere (CA) systems go further by actively managing the oxygen (O₂), carbon dioxide (CO₂), and nitrogen (N₂) levels inside transport containers, dramatically slowing the natural ripening and spoilage of produce during transit.

What are controlled atmosphere systems for transportation? 🔗

Controlled atmosphere systems for transportation are technologies that regulate the gaseous composition of the air surrounding perishable produce inside shipping containers or cargo holds during transit. Normal air contains roughly 21% oxygen and about 0.03% CO₂. CA systems alter this balance – typically by lowering oxygen and raising carbon dioxide – to create conditions that significantly reduce the metabolic activity of harvested fruits and vegetables.

The underlying principle is straightforward. After harvest, produce continues to respire: it takes in oxygen, releases CO₂, and generates ethylene, a hormone that accelerates ripening. By controlling these gas levels precisely, CA systems effectively slow down this biological clock, extending shelf life from days to weeks or even months.

Why CA transport matters for perishable produce 🔗

Traditional refrigerated (reefer) containers control temperature and sometimes humidity, but that alone is often insufficient for long-haul shipments. According to the Food and Agriculture Organization (FAO), approximately 14% of all food produced globally is lost between harvest and the wholesale market. CA transport directly addresses a large portion of these losses for horticultural produce.

Extended shelf life and quality retention 🔗

CA transport preserves the texture, colour, flavour, and nutritional value of produce over extended periods. For instance, apples and pears – the two most commercially significant commodities for CA – can be shipped over 30-45 day ocean voyages and arrive in excellent condition. Bananas transported under CA conditions can be harvested at a more advanced maturity stage, resulting in better flavour and higher field-level yields.

Reduced food waste and economic savings 🔗

The FAO notes that using modified atmosphere (CO₂-enriched air) for strawberry shipments reduced retail losses by roughly 50% compared to shipping in regular air. The economic loss from spoilage in air-shipped strawberries was estimated at $50-75 per pallet, far exceeding the $15-25 cost of using atmosphere modification. These numbers demonstrate a clear return on investment.

Enabling marine transport over air freight 🔗

CA technology allows produce that would otherwise require expensive air freight – due to its short postharvest life – to be shipped by sea at a fraction of the cost. The savings from switching to marine transport typically far outweigh the added expense of CA services, opening international markets to producers in developing countries.

Chemical-free pest control 🔗

CA combined with precision temperature management can control insects during transit without chemicals, a critical advantage for commodities heading to markets with strict pest quarantine regulations or those demanding organic certification.

How CA systems work in transport containers 🔗

A CA-equipped reefer container includes several core components: gas sensors (for O₂ and CO₂), a controller unit, a nitrogen generator or gas injection system, a CO₂ scrubber, and a fresh air exchange mechanism. Here is how the process typically works:

Once produce is loaded and the container sealed, the CA system modifies the internal atmosphere to pre-set levels appropriate for the specific cargo. Sensors continuously monitor O₂, CO₂, temperature, and humidity, and the controller makes automatic adjustments throughout the voyage. If oxygen drops too low, fresh air is introduced. If CO₂ rises above the target, scrubbers remove the excess. Some systems also inject nitrogen to displace oxygen more rapidly.

The ideal set points vary by commodity. Apples and pears generally require 1-3% O₂ and 1-3% CO₂. Strawberries benefit from CO₂ concentrations above 10-15%. Bananas, avocados, and mangoes each have their own specific requirements.

Major CA systems used in produce transportation 🔗

Several proprietary CA systems have been developed for commercial use in marine and overland transport. Three of the most notable are the Oxytral system, the Tectrol system, and the CONAIR-Plus system.

The Oxytral system 🔗

The Oxytral system is one of the most widely adopted CA technologies for maritime shipping. It works by generating nitrogen from ambient air using membrane separation technology. As nitrogen floods the container, oxygen is displaced to the desired low range – typically 1-5% depending on the produce type. Simultaneously, a CO₂ scrubbing unit removes excess carbon dioxide produced by the respiring cargo.

The system uses automated sensors and controls that continuously monitor and adjust gas concentrations. It is especially popular for transporting apples, pears, and stone fruits on long ocean routes, where maintaining stable low-oxygen conditions over several weeks is essential.

The Tectrol system 🔗

Developed by TransFresh Corporation (originally formed by Whirlpool in 1966), the Tectrol system takes a different approach. It focuses on precise gas mixing and active atmosphere modification inside 20-ft and 40-ft shipping containers.

A compact electronic controller – housed in a sealed enclosure within the container – is programmed by TransFresh technicians to maintain the exact atmospheric composition specified for the commodity being shipped. The system includes a CO₂ scrubber box that uses a hydrated lime filter bed. When CO₂ levels exceed the target, a fan pushes the container air through the lime bed, scrubbing out excess carbon dioxide.

Research from the University of California-Davis and Florida State University found that strawberries transported in the sealed Tectrol pallet system – with CO₂ concentrations maintained at 11-16% – showed significantly less decay (3-7% reduction) compared to other pallet cover systems. The Tectrol system is particularly effective for berries, and TransFresh has expanded its applications to include blueberry storage using breathable membrane technology.

One notable advantage of the Tectrol system is its flexibility. It can handle varying load sizes and mixed cargo types, and some configurations can create different atmospheric zones within a single container, allowing simultaneous transport of produce with different CA requirements.

The CONAIR-Plus system 🔗

The CONAIR-Plus system represents a newer generation of CA transport technology that integrates smart monitoring and predictive analytics. Beyond controlling atmospheric conditions, this system uses data from past shipments to optimise gas management strategies for specific routes and produce types.

What distinguishes CONAIR-Plus is its use of Internet of Things (IoT) connectivity. Logistics managers can monitor atmospheric conditions, temperature, and produce quality indicators remotely in real time, making adjustments from anywhere in the world if conditions deviate from optimal ranges. This level of remote oversight is especially valuable for high-value produce shipments where quality premiums justify the additional technology investment.

Other commercial CA technologies for transport 🔗

Beyond these three systems, several other technologies are used in commercial CA transport:

Carrier Transicold’s XtendFRESH is an integrated system that monitors and controls O₂ and CO₂ while also removing ethylene – the ripening hormone. Unlike some competitors, it does not require external ethylene filters or disposable scrubbing materials. It works best for high-respiring commodities like bananas, avocados, mangoes, asparagus, and raspberries.

Hapag-Lloyd’s ExtraFresh and ExtraFresh Plus are container-level CA solutions offered by the shipping line. The basic ExtraFresh system uses the cargo’s natural respiration to modify the atmosphere, while ExtraFresh Plus adds active nitrogen and CO₂ injection before and during the voyage. These are particularly beneficial for low-respiring cargo like blueberries that cannot generate sufficient CO₂ through their own respiration alone.

Dynamic Controlled Atmosphere (DCA) is an emerging refinement where the system continuously adapts O₂ and CO₂ levels based on real-time feedback from the produce itself. If the system detects low-oxygen stress in the cargo, it automatically increases O₂ until the produce returns to its optimal physiological state. DCA can extend storage and transit life beyond what traditional static CA achieves.

Produce-specific CA requirements during transport 🔗

Different commodities have very different atmospheric needs. Getting the balance wrong can cause physiological disorders, off-flavours, or accelerated decay rather than preservation. Here are typical CA parameters for commonly transported produce:

Apples and pears: 1-3% O₂, 1-3% CO₂. These are the most commercially established CA commodities, and CA transport is often used to continue the CA chain after months of CA storage post-harvest.

Bananas: 2-5% O₂, 2-5% CO₂. CA transport allows bananas to be harvested at greater maturity for better taste while still arriving in good condition after voyages of up to 45 days.

Avocados: 2-5% O₂, 3-10% CO₂. CA helps reduce chilling injury, enabling lower shipping temperatures (around 5°C) than would be safe in regular air.

Strawberries and berries: High CO₂ (10-15%) is critical for controlling grey mould (Botrytis). The Tectrol system has been especially effective in this segment.

Mangoes, kiwifruit, cherries, and stone fruits: Each has unique requirements, generally in the range of 2-5% O₂ and 5-10% CO₂, though specifics vary by cultivar and destination market.

Challenges and limitations of CA transport 🔗

Despite clear benefits, CA transport faces several practical challenges. The technology adds cost – both for equipment and for the technical expertise required to programme and maintain systems correctly. According to one industry review, fewer than 2% of the world’s refrigerated containers are fitted with stand-alone CA technology, although about 25% are capable of some form of atmosphere modification.

CA systems can only deliver their full potential when the entire cold chain is managed correctly. The produce must be harvested at the right maturity, precooled promptly, packed properly, and maintained at the recommended temperature throughout. A break at any point in this chain undermines the benefits of atmospheric control.

Incorrect CA settings can cause more harm than good. Oxygen levels that are too low can trigger fermentation and off-flavours. Excessively high CO₂ can cause tissue damage in sensitive commodities. This is why accurate sensors, proper calibration, and commodity-specific protocols are essential.

The future of CA in produce logistics 🔗

The direction of development in CA transport is toward greater precision, automation, and connectivity. Dynamic CA systems that respond to real-time produce physiology, IoT-enabled remote monitoring, and predictive analytics driven by shipment data are all moving from niche applications into mainstream use.

As global trade in perishable produce continues to expand – and as pressure mounts to reduce food loss and waste – the role of CA systems in transportation will only grow. The integration of respiratory quotient control, improved gas scavengers, and natural additives are among the innovations improving both conventional CA and modified atmosphere packaging for transit.

For producers, logistics companies, and retailers, investing in CA transport is increasingly not just a quality decision but a financial and sustainability imperative.

What do you think? As CA technology becomes more accessible, could it help smallholder farmers in developing countries access premium export markets – and what would be the biggest barrier to adoption in your view?

References

1. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/controlled-atmosphere-storage
2. https://www.fao.org/4/y5431e/y5431e06.htm
3. https://senmatic.com/knowledge/sensor/sensors-ensure-fresh-produce-from-farm-to-table-in-refrigerated-containers/
4. https://www.marinelink.com/article/maritime-security/technology-transfreshs-controlled-atmosphere-609
5. https://theproducenews.com/researcher-confirms-benefits-tectrol-reducing-strawberry-decay
6. https://www.foodlogistics.com/transportation/cold-chain/article/12368796/carrier-transicold-div-controlled-atmospheres-enable-fresh-produce-to-reach-distant-and-new-consumers
7. https://www.ingentaconnect.com/content/sphs/sphr/2006/00000002/00000005/art00003;jsessionid=9c8ec0afa1177.x-ic-live-03
8. https://technology.matthey.com/article/62/1/107-117/