Our Dynamically Controlled Atmosphere

Look inside our Dynamically Controlled Atmosphere storage with Frank, the steward of Puratos Fourayes sleeping apples…

25 Jul 2023


I’m Frank, the Plant Core Services Infrastructure Manager at Puratos Fourayes, but I am known as the steward of the sleeping apples. I look after the apples in the Dynamically Controlled Atmosphere Stores (DCA), a storage system that Fourayes was a pioneer of, having been the first to use it for Bramley apple storage.


What is a DCA and how does it work?

A DCA is a storage system which stores fruit, in this case Bramley apples, at the optimum conditions. It’s constantly adjusted based on the fruit’s respiratory activity. An oxystat system checks oxygen, carbon dioxide levels and monitors the temperatures.

Within the DCA plant room there are compressors, which allow for efficiency in the summer months when the temperature is high, and this can help to regulate high fruit temperature. These compressors also allow for the diversion of power to each store, which lowers the temperature in the store therefore keeping the fruit vibrant, crisp, and fresh.

Through running harvest watch, we can measure the alpha light levels which come off from the apples, allowing for a combination of equipment and software to keep the fruit as fresh as the day it was picked.

It's so fresh that you can't even tell the difference between DCA fruit and fruit picked on the day!

What are the benefits vs other types of storage?

One of the benefits of a DCA store, compared to an Ultra-Low Oxygen Storage, is that it can be more efficient. As well as helping to regulate high fruit temperature, the DCA is also more efficient in its use of compressors.

The DCA can use one compressor and one head to man 6 coolers in the stores. The energy efficiency is evident as one compressor runs 6 of the coolers; our compressor is more environmentally friendly than the traditional 1 compressor to each store. In the harvest period, we can use all this power whenever we need it, creating a more efficient process.


How much fruit can be stored in the DCA?

Our DCA stores can store up to 1000 tonnes of Bramley apple; other stores use rotational stock much more quickly.

Although traditional ultra-low oxygen storage has a higher capacity for storing fruit, the DCA can store fruit for much longer; up to 13 months! This is 3 or 4 times longer than under normal conditions.

DCA’s provide a more sustainable, more efficient, and more reliable way of storing fruit; our stores are tested every 6 minutes, compared to the older systems which tested every hour.


How do the apples go to sleep and wake up?

If we use the analogy of apples as sentient beings able to fall into a deep slumber, it is easier to imagine the process. To put the apples into a deep sleep, we must allow up to 6 weeks.

The sleep that they are in keeps them fresh with no chemicals, as they are stored at ultra-low atmosphere levels.

The ideal atmospheric conditions vary for different fruits, but the aim is to have around 0.5% of oxygen, 1% of carbon dioxide and a nitrogen generator is in the store to ensure that the levels do not get too high or too low.

If the atmosphere in the store goes outside of specification, there is no problem because the atmosphere concentration will be immediately amended if it threatens to get too low or too high as the stores are constantly monitored.

In the photograph of the sleeping apples, there is a white film surrounding them. This is called ‘Surround’, a form of sun cream for apples which is sprayed on them during the hotter months to protect them from the heat.

When oxygen is put back into the DCA stores, the apples awaken from their 13-month slumber

Our DCA stores are more beneficial than chemically stored fruit because of the controlled respiration of the apples, meaning that no ethylene is produced. However, in other, chemical storage solutions, chemicals block the receptors of the apples which would make it more difficult to tell if there is ethylene in the store. If one apple rots, all the apples rot as they will all produce and be affected by the ethylene. However, in a DCA, if one apple is rotten, it won’t rot the surrounding apples.

The photographs show the apples in the DCA store. In the green net bags at the front of the DCA store, there are some Bramley apples which can be used as samples. These are taken out and tested to measure the quality, colour, apple pressure, taste, and juiciness of the apples on the inside.


Fun Fact

In the photograph of the sleeping apples, there is a white film surrounding them. This is called ‘Surround’, a form of sun cream for apples which is sprayed on them during the hotter months to protect them from the heat.

Thanks for reading, 

Frank, the steward of the sleeping apples