The keys to successful preservation

The drying of onions, nuts, and potatoes is a crucial post-harvest step that determines the profitability of the farm and the final quality of the products. Once extracted from the soil, these products are still alive: they breathe, give off heat, and are saturated with moisture. Without strict and immediate control of the ambient air, health risks explode: mold, gray rot, mildew development, or early germination. At Climatik, we support producers with customized ventilation, heating, and dehumidification solutions to transform a raw harvest into a product that can be stored long-term.

Why is drying vital for your produce?

The primary objective of drying onions, nuts, and potatoes is to reduce water activity on the product surface to stop the development of microorganisms. However, each crop has radically different physiological needs that must be strictly respected to avoid degrading the produce.

1. Onions: The challenge of rapid curing

Onions are composed of nearly 90% water. Immediately after harvest, they must undergo what is called "curing." This involves drying the outer skins and, especially, closing the neck (the top part of the onion). If the neck remains moist, bacteria rush in and cause the onion to rot from the inside. Effective drying requires a constant flow of warm air to remove this surface moisture in less than 48 to 72 hours.

2. Walnuts: Preserving oil qualities

Walnuts are fruits rich in fats. If drying is too slow, residual moisture causes rancidity of the lipids and the appearance of internal molds invisible to the naked eye. Conversely, overly aggressive drying at high temperatures can crack the shell or cook the kernel, making it unfit for sale. Precise thermal setting is the absolute priority here.

3. Potatoes: Curing and sugar management

For potatoes, the term "drying" is often associated with "suberization" (curing). This involves drying the residual soil and promoting the healing of wounds received during harvesting. A poorly dried potato will condense when refrigerated, which will trigger widespread soft rot in the storage building.

Advanced techniques for efficient drying

Forced high-pressure ventilation

For drying onions, nuts, and potatoes, a simple airflow is not enough. Air must pass through the mass of products stored in bulk or in pallet boxes. This requires fans capable of overcoming the "pressure drop" (the resistance offered by the pile of vegetables). At Climatik, we recommend high-power axial fans to ensure that air circulates even in the center of the storage cells.

Dehumidification by adsorption or condensation

Relying solely on outside air is risky. If the weather is rainy or foggy, ventilating your shed is tantamount to bringing in additional moisture. Using an industrial dehumidifier allows for air treatment in a closed circuit.

• The condensation dehumidifier is ideal for temperatures above 15°C.

Gas heating: Power and responsiveness

For certain crops like onions, the speed of temperature rise is crucial. The use of gas-fired hot air generators (direct or indirect combustion) offers major advantages for agricultural operations:

·         Instant temperature rise: Unlike electric systems, gas allows for very quickly reaching the 25°C or 30°C necessary to close onion necks in less than 72 hours.

·         Relative humidity control: By heating the air, its relative humidity is mechanically decreased, which increases its capacity to "absorb" the water contained in the products.

·         Flexibility and mobility: Gas-fired hot air cannons are often mobile, allowing different storage cells to be treated according to harvest needs.

·         Energy efficiency: Gas remains an efficient energy source for treating large volumes of air in record time, thus limiting the operating time of the machines.

Technical note: For drying sensitive products, Climatik often favors indirect combustion generators (with a chimney). This ensures that no combustion residues or excess moisture related to the flame come into contact with the harvest, thus ensuring total air purity.

Technical Guide: Parameters for Success

Successful drying of onions, nuts, and potatoes requires juggling three variables: airflow, temperature, and humidity.

Calculation of airflow requirement

The golden rule in the agricultural sector is to size ventilation according to the stored volume. For onions, it is generally calculated as:

D = V x 150

Where D is the airflow in m³/h and V is the volume of products in m³. An undersized installation will leave "dead zones" where heat will accumulate, leading to dry losses of merchandise.

Recommended Temperatures

The Economic Aspect: Why Invest in Climatik Equipment?

Energy cost is a major concern for modern farms. Running fans and heaters consumes energy. However, the cost of a lost harvest is infinitely higher.

1. Reduction of losses: An optimized drying system can reduce storage losses from 15% to less than 2%. For a harvest of several hundred tons, the investment pays for itself in a single season.

2. Quality gain: Well-dried products retain their visual appearance (shine of the onion skin, light color of the walnut kernel), allowing them to be sold at a premium price in demanding markets.

3. Energy optimization: Climatik machines are equipped with speed variators and control sensors. The system only activates when the humidity exceeds the critical threshold, thus avoiding any electrical waste.

Maintenance and monitoring of installations

Good drying of onions, nuts, and potatoes does not stop with the installation of machines. Daily monitoring is necessary:

• Filter verification: In agricultural environments, soil dust and plant debris quickly clog ventilation grilles. Weekly cleaning is imperative to maintain airflow.

• Probing the heart of the pile: Use long probe thermometers to check that the temperature in the center of your pallet boxes does not rise abnormally, a sign of ongoing fermentation.

• Condensation management: Ensure that extracted humid air is not re-aspirated by the intake fans.

Conclusion: Make air your best ally

The drying of onions, nuts, and potatoes is a science that leaves nothing to chance. Mastering the indoor climate of your buildings is a direct extension of your work in the field. By choosing Climatik air treatment solutions, you equip yourself with robust, reliable equipment designed for the constraints of the agricultural world.

Do you have a project to create a drying cell or do you wish to modernize your current equipment? Our technical experts are at your disposal to carry out a complete thermal assessment and guide you towards the most efficient solution. With Climatik, ensure the sustainability of your harvests and the serenity of your farm.