We’ve all at one point or another heard the idiom “One bad apple, ruins the bunch”. This particular saying is directly related to the effect that one overripe apple can have on the accompanying apples, as it continues to emit ethylene into the surrounding atmosphere, accelerating the ripening and senescence of the entire bunch in the process.

So, what exactly is Ethylene and how is it being utilised to maximise the outgoings of fruits & vegetables across global supply chains?

What is Ethylene?

Ethylene is the most commercially produced organic compound in the world and is used in many industrial applications.

Without scent and invisible to the eye, Ethylene (C2H4) is a small hydrocarbon gas and a naturally occurring hormone produced by plants that aids in the ripening and ageing process of fresh produce. Fruits such as apples and pears emit a greater amount of ethylene gas, which as a result affects their ripening process. Other fruits, like cherries or blueberries, produce very little ethylene gas, therefore, they do not greatly impact the ripening process.

Due to ethylene being so important for the ripening of some fruits and vegetables, it is sometimes used by commercial agribusinesses to speed up the ripening process of crops.

What are its effects on Fruits and Vegetables?

While ethylene is invaluable due to its ability to initiate the ripening process in several fruits and vegetables, it can also be very harmful to many fruits, vegetables, flowers, and plants by accelerating the ageing process and decreasing the product quality and shelf life. The degree of damage depends upon the concentration of ethylene, length of exposure time, and product temperature.

Fruits and vegetables play a vital role in human nutrition. One of the few factors that influence their economic value is the relatively short ripening period and reduced postharvest life they often have. Over-ripening of fruits and vegetables leads to excessive softening which results in spoilage and damage during shipping and handling. Slowing the process of ripening and quality deterioration extends the storage and shelf life of fresh fruits and vegetables. Monitoring the shelf life of fresh produce not only helps the grower to save on postharvest losses but consumers also benefit in terms of retained freshness over longer periods, resulting in value addition to the fruits and vegetables.

Understanding the fundamental relationship between ethylene and fruit respiration rates during ripening is necessary in order to manage the harvesting, storage, and distribution processes.

When the chemical is exposed to fresh produce, it latches on to its ethylene receptors and stimulates the maturing stages of the produce. The chemical reaction within fruits and vegetables then brings forth the development of flavours, vitamins, firmness, aroma, texture, and colour in the produce. However, too much Ethylene exposure before shipments meet their required timelines and destinations, can lead to overripeness, a decline in product quality, and an increase in Volatile Organic Compounds (VOCs) throughout the stock.

One of the biggest contributors to mass amounts of waste within the fresh produce sector is directly linked to cases of overexposure to ethylene during the ripening and storage process. On a global scale, the main contributor to food waste is fruits and vegetables with an astounding 45-50% of all harvested fresh produce being lost or wasted within the food supply chain. This is roughly 1.3 billion tonnes of food, which equates to $680 Billion US Dollars of wasted fresh produce each year.

The effects of ethylene on vegetables can be avoided or reduced by:

Low-temperature storage. Below 5°C, the effects of ethylene are greatly reduced.
Keeping the storage area ventilated to avoid an accumulation of ethylene inside.
Removing ethylene from storage rooms by reacting it with potassium permanganate (KMnO3).
Oxidising ethylene by reacting it with ozone (O3).
Storage in an atmosphere with high CO2.
Air scrubber systems for storage cleansing.

Conventional Practices are Harmful to Fruits and Vegetables

Any closed environment, such as truck trailers, shipping containers, warehouses, and cold rooms, will have a similar effect resulting in increased concentration of Ethylene.

At the latter part of post-harvest, artificial ripening by using ethylene gas is a general practice as it ensures that the fresh produce reaches the retail outlets with a degree of ripeness, which brings out its best in terms of taste, colour, texture and nutritional value. One of the most common examples is the ‘forced’ ripening of bananas during high demand periods.

However, these conventional methods adopted by most warehouses and cold stores of lowering the temperature and humidity and using gases like nitrogen and sulphur increase the shelf life but have several disadvantages.

It uses toxic gases
It is dangerous for human health
It changes the natural properties of fruit as well

Refrigeration and humidity control slow decay but are not enough to halt the production of ethylene gas in cold stores and warehouses. Even a small amount of ethylene gas during storage is enough to hasten the process of decay of fresh produce. This makes ethylene control absolutely necessary in the cold chain.