Controlling Ethylene Levels to Extend Shelf Life of Produce

Ethylene is a tiny gas molecule with an outsized impact on the fresh produce industry. This naturally occurring plant hormone (C₂H₄) triggers ripening, accelerates senescence, and can turn a warehouse full of crisp fruits into a pile of mushy waste in a matter of days. For farmers, distributors, and retailers, controlling ethylene levels in storage environments is not just a technical concern – it is a critical economic necessity. Effective ethylene management can extend the shelf life of produce, reduce food waste, and keep fruits and vegetables market-ready for longer periods.

Why ethylene control matters in postharvest management 🔗

After harvest, fruits and vegetables continue to carry out metabolic processes, including respiration and ethylene production. Ethylene accelerates ripening and triggers chlorophyll degradation, softening of tissues, and eventually spoilage. Even trace amounts – as low as 0.1 parts per million (ppm) – can initiate physiological changes in sensitive produce. This is especially true for climacteric fruits like bananas, mangoes, apples, and tomatoes, where ethylene drives a sharp spike in respiration known as the climacteric rise.

Without proper ethylene management, produce loses firmness, flavour, and nutritional value well before it reaches consumers. The economic consequences are significant: increased waste, reduced marketability, and higher costs along the supply chain. That is why the postharvest industry invests heavily in strategies to either remove ethylene from storage environments or inhibit its production and action within the produce itself.

Removing ethylene sources from storage 🔗

The simplest starting point in any ethylene control strategy is to minimise the sources of ethylene in the storage environment. This involves a set of practical, low-cost measures that can be implemented at any scale of operation.

Segregating ethylene-producing and ethylene-sensitive produce 🔗

Not all fruits and vegetables behave the same way when it comes to ethylene. Some, like apples and bananas, are prolific ethylene producers. Others, like lettuce, broccoli, and cucumbers, are highly sensitive to ethylene but produce very little of it. Storing these two categories together is a recipe for rapid deterioration of the sensitive items. For instance, keeping apples and avocados in the same storage area can cause both to ripen and deteriorate far faster than they would separately.

A straightforward solution is to store ethylene producers and ethylene-sensitive items in separate rooms or containers. This segregation alone can meaningfully reduce the ambient ethylene concentration and slow down unwanted ripening across the inventory.

Maintaining storage hygiene 🔗

Overripe, damaged, or decaying produce acts as a concentrated source of ethylene gas. Regular inspection and removal of such items from cold stores and warehouses can help keep ethylene levels in check. Additionally, using electric forklifts instead of fuel-powered ones is advisable, as the exhaust from vehicles burning hydrocarbons can introduce additional ethylene into the storage atmosphere.

Ventilation 🔗

Adequate air exchange helps flush out accumulated ethylene from storage areas. Ethylene levels can be controlled by ventilation or by using scrubbers, and even in areas where produce is not stationary for long, ethylene concentrations can build up quickly. However, ventilation alone has its limits – it is unsuitable for sealed controlled-atmosphere rooms, and excessive air exchange can increase weight loss in produce.

Chemical removal of ethylene 🔗

When source management and ventilation are not enough, chemical methods can actively scrub ethylene from the storage atmosphere. Two of the most established approaches use potassium permanganate and activated charcoal.

Potassium permanganate (KMnO₄) 🔗

Potassium permanganate is one of the most widely used ethylene-scavenging agents in the postharvest industry. It works by oxidising ethylene gas into carbon dioxide and water, effectively neutralising it. The compound is typically loaded onto a porous carrier material such as alumina beads, zeolite, or silica, which increases the surface area available for the reaction.

In practice, KMnO₄-impregnated sachets or filters are placed inside packaging or within storage rooms. As ethylene comes into contact with the permanganate, it is chemically broken down. A visible colour change from purple to brown indicates that the KMnO₄ has been consumed and needs replacement. Research published in Food Engineering Reviews confirms that KMnO₄ has been used for nearly 50 years in food packaging systems, with over 70 studies demonstrating its effectiveness on climacteric fruits.

One important consideration: KMnO₄ is toxic and must not come into direct contact with produce. It is always used in enclosed sachets or embedded in packaging material at a safe distance from the food.

Activated charcoal and other adsorbents 🔗

Activated charcoal (also called activated carbon) works through physical adsorption. Its highly porous structure traps ethylene molecules on its surface, removing them from the surrounding atmosphere. Zeolites – naturally occurring aluminosilicate minerals – function similarly and are sometimes used in combination with other materials for enhanced performance.

These adsorbents are often incorporated into packaging materials or small sachets placed inside produce containers. While they do not chemically destroy ethylene like potassium permanganate does, they effectively reduce its concentration in the immediate vicinity of the produce.

Advanced storage techniques 🔗

Beyond chemical scrubbers, two advanced storage technologies offer powerful control over ethylene levels: controlled atmosphere (CA) storage and hypobaric storage.

Controlled atmosphere storage 🔗

Controlled atmosphere storage involves precisely regulating the gas composition inside a sealed storage room. Typically, oxygen levels are reduced to around 2-3%, while carbon dioxide is raised to 5-15%. Temperature and humidity are also carefully maintained.

This combination of low O₂ and elevated CO₂ significantly slows down respiration, which in turn reduces ethylene production. Studies have shown that specific CA conditions can suppress ACC-oxidase activity – the enzyme responsible for the final step of ethylene biosynthesis – resulting in markedly lower ethylene output and extended storage life.

CA storage is already standard practice for many high-value commodities. For example, apples stored in CA rooms can remain fresh for months beyond their normal shelf life. The rooms are sealed with airtight joints and require continuous gas monitoring to maintain the correct atmosphere. If oxygen falls too low or CO₂ rises too high, the produce can switch to anaerobic respiration, which causes off-flavours and tissue damage.

Hypobaric storage (low-pressure storage) 🔗

Hypobaric storage takes a different approach: it reduces atmospheric pressure inside a refrigerated chamber to levels well below normal. Operating at pressures typically below 50 kPa, this technique lowers the partial pressure of oxygen and flushes out ethylene and other volatile metabolic by-products through continuous ventilation.

Research conducted at Wageningen University & Research has demonstrated the potential of hypobaric storage for highly perishable produce like blueberries and roses, showing reduced decay, less shrivelling, and lower weight loss compared to conventional cold storage.

The results with specific commodities are striking. Under hypobaric conditions, bananas that normally last 10-14 days in cold storage can be stored for up to 90-150 days. Similarly, strawberries can extend from about 5-7 days to 21-28 days. However, the technology requires specialised equipment – vacuum pumps, sealed refrigerated chambers, and precise monitoring systems – making it a costly option best suited for high-value produce and long-distance transport.

Inhibiting ethylene biosynthesis 🔗

Rather than removing ethylene after it has been produced, another strategy targets the biological pathway that produces it in the first place. Several chemical compounds can block key steps in the ethylene biosynthesis pathway.

Aminoethoxyvinylglycine (AVG) 🔗

AVG is one of the most effective inhibitors of ethylene biosynthesis. It works by competitively inhibiting ACC synthase, the enzyme that catalyses the conversion of S-adenosylmethionine (SAM) to 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene. By blocking this rate-limiting step, AVG can substantially reduce ethylene production in treated plants.

Commercially marketed as ReTain® by Valent BioSciences, AVG has been registered as a plant growth regulator for apples since 1997 and is now widely used by fruit growers worldwide. Preharvest sprays of AVG have been shown to reduce fruit drop, maintain firmness, and extend cold-storage potential in varieties like Gala and McIntosh apples.

It is worth noting, however, that AVG does not block ethylene perception – treated produce can still respond to externally applied ethylene. Also, there can be trade-offs with fruit quality. Some studies have reported reduced aroma volatile production in AVG-treated apples, which could affect consumer acceptance.

1-Methylcyclopropene (1-MCP) 🔗

While not an inhibitor of ethylene biosynthesis per se, 1-MCP deserves mention here because it is the other major commercial tool for ethylene management. 1-MCP works by binding irreversibly to ethylene receptors in plant tissues, effectively making the produce unable to perceive or respond to ethylene. Marketed as HarvistaTM and SmartFresh, it is widely applied to apples, avocados, tomatoes, and other climacteric crops both before and after harvest.

The combination of AVG (to reduce ethylene production) and 1-MCP (to block ethylene perception) provides a powerful two-pronged approach to ethylene management in commercial horticulture.

Emerging technologies for ethylene management 🔗

The field of ethylene control is not standing still. Several newer approaches are gaining attention in research and early commercial applications.

Photocatalytic oxidation 🔗

This technique uses semiconductors like titanium dioxide (TiO₂) that, when exposed to UV light, generate highly reactive electron-hole pairs capable of breaking down ethylene into CO₂ and water. A study published in Horticulturae showed that combining KMnO₄ filters with UV-C radiation and TiO₂ significantly improved the postharvest quality of broccoli stored alongside ethylene-producing tomatoes.

Active packaging with ethylene scavengers 🔗

The incorporation of ethylene-scavenging materials directly into packaging films is an area of growing commercial interest. Materials like nano-zeolites, palladium-promoted adsorbents, and KMnO₄-loaded nanocomposites can be embedded into polyethylene or biopolymer films, creating smart packaging that actively manages the atmosphere around each individual item of produce.

Ozone-based systems 🔗

Ozone (O₃) is a strong oxidising agent that can decompose ethylene. Commercial ozone-generating systems circulate ethylene-laden air from the storage room through a reaction chamber where ozone breaks it down. While effective, controlling ozone concentration is critical – high levels can damage produce and pose health risks to workers.

Choosing the right ethylene control strategy 🔗

No single ethylene control method is universally best. The right approach depends on several factors: the type of produce, scale of operation, distance to market, budget, and desired shelf-life extension. Small-scale operations may find that source management, ventilation, and KMnO₄ sachets are sufficient. Large commercial cold chains might invest in controlled atmosphere rooms, 1-MCP treatments, and active packaging solutions.

In many cases, the most effective strategy is a combination of methods – for example, storing segregated produce in CA rooms while also using KMnO₄ filters and treating high-value items with 1-MCP. Such an integrated approach addresses ethylene at multiple points: its production, its accumulation in the environment, and its action on plant tissues.

Understanding ethylene behaviour is essential for anyone involved in the postharvest chain. With global food loss estimated at around 1.6 billion tonnes annually – a significant portion of which occurs after harvest – getting ethylene management right is both an economic and environmental imperative.

What do you think? With so many ethylene control technologies available today, which method do you believe offers the best balance of cost and effectiveness for small and medium-scale produce operations? And as active smart packaging becomes more accessible, could it eventually replace traditional cold-chain approaches altogether?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC8877706/
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5. https://link.springer.com/article/10.1007/s12393-019-09193-0
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7. https://www.mdpi.com/2311-7524/10/8/840
8. https://www.freshknowledge.eu/en/research-results/hypobaric-storage-of-fresh-produce-and-flowers.htm
9. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/aminoethoxyvinylglycine
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