Choice of fruit storage technology: ULO or DCA

Modern Fruit Storage: Why It Matters and How Advanced Technologies Reduce Post-Harvest Losses

It’s the 21st century, and store shelves are filled with fruits of every kind - from apples to mangoes available year-round. But it hasn’t always been this way. Only through modern growing, storage and transport technologies can consumers enjoy fresh fruit in any season.

Today we’ll look closely at one critical link in this supply chain: storage - the stage that determines fruit quality, flavor, market value and profitability. When storage conditions are poorly designed, physical and quality losses can reach up to 80% of total production.

Around 50% of the harvest must be sold immediately during the picking season, which means many growers lose profit simply because they lack modern storage facilities capable of keeping fruit fresh for 8–12 months. Unfortunately, this shortage of specialized fruit storage remains a challenge for many regions across India, Africa and the Middle East.

Before Choosing a Fruit Storage Facility, Ask Yourself:

What storage capacity do you need?
Which varieties do you grow?
What is your daily harvest volume?
What are your sales and distribution goals?

For long-term storage, fruit must be placed in conditions that significantly reduce respiration, since slower respiration extends shelf life, preserves nutritional value and maintains appearance.

This is where controlled-atmosphere storage (CA / RGS) comes in - a technology that adjusts oxygen, carbon dioxide and humidity levels to slow natural ripening. CA technology is essential for industrial fruit production, especially for apples.

Within controlled atmosphere systems, two modern technologies dominate the industry:

ULO (Ultra Low Oxygen)
DCA (Dynamic Controlled Atmosphere)

Let’s explore how they work.

Controlled Atmosphere (CA / RGS) Storage

Controlled atmosphere storage relies on a fully sealed chamber where temperature, humidity, oxygen and carbon dioxide are precisely regulated.

In normal air, the composition is:

78% nitrogen
21% oxygen
~0.03% CO₂

Inside a CA chamber, oxygen is reduced to 1.5–2.5%, slowing down fruit ripening - ideal for apples, pears and imported exotic fruits.

What Makes RGS Storage Different from Regular Cold Rooms?

Complete sealing of the chamber to prevent gas leakage.
Sealed, gas-tight entrance gates, pressed tightly against the chamber walls.
This is essential for maintaining stable atmospheric composition over long periods.

If you're planning to build a CA facility, start with several smaller chambers, especially if you grow different apple varieties - each variety requires separate storage.
Once a chamber is opened and depressurized, its fruit must be sold within 10–14 days.

ULO - Ultra Low Oxygen Storage

ULO technology reduces oxygen levels even further - down to 1.2% - to slow ripening and extend storage life.
However, the lower the oxygen level, the more carefully CO₂ must be controlled to avoid fruit injury.
This system is highly effective but requires constant monitoring.

DCA - Dynamic Controlled Atmosphere

DCA is considered the most advanced form of controlled atmosphere storage.

With extremely low oxygen levels, the fruit enters a metabolic “suspended state”, dramatically extending shelf life without losing taste, firmness or aroma.

However, not all fruits tolerate low oxygen well. Some varieties develop physiological disorders if pushed below their tolerance threshold.
Therefore, the minimum oxygen level must be selected individually for each variety.

How DCA Works

DCA relies on continuous measurement of three indicators:

Chlorophyll fluorescence
Alcohol accumulation inside the fruit
Respiration rate (ratio of CO₂ released to O₂ absorbed)

The most widely used and most expensive system is DCA with chlorophyll fluorescence sensors.
These sensors detect the fruit’s stress point — the lowest oxygen level the fruit can withstand.
Once the system detects stress, oxygen levels are increased slightly, preventing anaerobic respiration.

After determining the safe minimum oxygen threshold, the chamber is maintained just above this point for long-term storage.