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Ripening and metabolic processes in fruits are slowed down in controlled atmosphere (CA) chambers, thereby preserving the nutritional value and external appearance of the fruits. In a way, this can be likened to a state of dormancy. On average, fruits can be stored in a controlled gas environment for up to 6-9 months.

Apple is arguably one of the most popular fruits in our regions. There are various varieties and flavors, but the essence remains unchanged: the fruit is packed with beneficial vitamins.

To preserve the original appearance and flavor of apples, they need to be stored correctly according to technological standards. Achieving the best outcome is aided by apple storage facilities, where optimal conditions for preservation are created.

With proper ventilation, temperature, humidity, storage methods, and other factors in place, apples do not rot, they don't dry out, and they retain both their flavor and full set of vitamins.

After harvesting, fruits continue to live; they respire, meaning they absorb oxygen and release carbon dioxide. The storage period can be extended by reducing the intensity of respiration. To achieve this, produce is typically cooled. However, this isn't always sufficiently effective. Cooling must be accompanied by additional methods, one of which is maintaining specific levels of oxygen and CO2.
Reducing the presence of oxygen in the chamber has an inhibitory effect on the fruit's oxidation process, yet there's a certain threshold below which anaerobic respiration resumes. Hence, it's crucial to maintain the oxygen content in the chamber as close to the minimum level as possible, individualized for each type of produce.
Another physiological effect is the gradual conversion of sucrose into fructose, which, during fruit storage in an environment with elevated CO2 content, is slowed down. As a result, the fruit retains its firmness and most of its components. This also explains why fruits stored in a controlled atmosphere maintain their quality over a significant period.

Storage in a controlled atmosphere leads to a 2-3 times reduction in the intensity of metabolic processes, significantly extending the storage period. At the end of storage, the fruits remain as tasty and fresh as they were at the beginning.

The application of controlled atmosphere for storing grapes, oranges, lemons, kiwis, apples, pears, tomatoes, and cabbage yields excellent results. Therefore, in the present day, the construction of new cold storage units or vegetable storage facilities, as well as the reconstruction and modernization of existing ones, involves the implementation of a Controlled Gas Environment for the long-term preservation of fruits and vegetables.

Controlled atmosphere allows for reducing the concentration of oxygen, thus slowing down vital processes. Simultaneously, it's essential to control the level of carbon dioxide, which should be slightly above 5%. The nitrogen content is increased. Such an environment extends the storage period to 6-9 months or even longer.

Advantages of using Controlled Atmosphere:

  • The natural color of fruits is preserved – carbon dioxide stabilizes the product's color.
  • The drying process of stored produce is reduced – controlled atmosphere inhibits the development of tissue diseases and growth of fungal colonies. With the right concentration, a threefold decrease in losses is possible.
  • Natural density is maintained – the modified atmosphere prevents pectin breakdown.
  • The storage period is extended – reduced oxygen can't activate tissue decay processes.
  • The natural taste and aroma are preserved – the new atmospheric composition blocks the formation of volatile compounds and suppresses ethylene synthesis, while also inhibiting fermentation.

Technologies for creating a Controlled Atmosphere

Several technologies are commonly used for applying controlled atmosphere storage:

  • CA (Controlled Atmosphere). This is the simplest type of controlled atmosphere chamber setup. It involves rapidly reducing the oxygen content in the chamber (from 21% to 5% within 36 hours) and maintaining specific low levels of oxygen and CO2.
  • ULO Atmosphere (Ultra Low Oxygen). ULO ensures preservation with an oxygen content of about 1%. This technique incorporates a carbon dioxide adsorber and a nitrogen generator.

The choice of the type of atmosphere used depends on the product's (type, variety) and its physiological condition at the time of harvest.

ULO offers advantages over traditional CA methods by further reducing respiration rates (by 30%), especially in the case of apples and pears, while simultaneously controlling critical physiological conditions like scald and internal browning. This improvement in preserving fruit firmness extends the product's storage period.

Furthermore, since 2003, the Dynamic Controlled Atmosphere (DCA) storage method has gained popularity. This method is highly effective but involves costly chamber equipment. It incorporates a control system that maintains minimal oxygen concentration. The atmosphere composition can be changed rapidly and precisely. To achieve such an extreme atmosphere, Isolcell Italia S.p.A. has developed a new generation of sophisticated equipment, including the intelligent IS absorber.

Designing a Controlled Atmosphere

The proper selection of refrigeration equipment and ventilation systems plays a crucial role in designing a controlled atmosphere for fruit and vegetable storage facilities. The controlled atmosphere is established through specialized and individually tailored equipment arrangements.

To ensure the functionality of the controlled atmosphere system, we offer equipment from Isolcell Italia S.p.A.:

  • Storage mode management system that controls equipment based on oxygen, carbon dioxide, temperature, humidity levels, etc., to maintain optimal conditions for extended preservation of vegetables and fruits.;
  • Nitrogen (N2) generator, reducing oxygen levels. Available as a membrane or adsorption unit;
  • Carbon dioxide (CO2) adsorber, removing excess carbon dioxide produced by the fruits and maintaining the desired CO2 level in the storage;
  • Sulfur dioxide (SO2) adsorber, eliminating sulfur dioxide which is used to combat disease-inducing environments, e.g., for grape storage;
  • Ethylene adsorber/catalytic converter, utilized in LECA technology.;
  • Gas analyzers (atmospheric gas analysis system), measuring oxygen (O2) and carbon dioxide (CO2) concentrations.
  • Automation, humidifiers, sensors, and other related equipment.

Furthermore, refrigeration chambers, rooms, and storage facilities for vegetables that utilize controlled atmosphere technology must be airtight. Therefore, the doors to the chamber or storage room play a crucial role in ensuring airtightness.

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