Why you should avoid using reefer containers for your postharvest cooling operations. 

The cold chain, consisting of pre-cooling, refrigerated storage, and refrigerated transport – is one of the pillars of post-harvest handling. Despite this, the systems are still weak or nonexistent in some countries. Whether enterprises are growing and packing or processing for the local and export market, cooling solutions are vital to guarantee sustainability, viability and revenues. It is critical to cool down the harvest as soon as possible, and to do it in the right way, as this process impacts the end quality, weight and shelf life. In return, this is fundamental to sell more at better prices and generate higher Returns on Investment (ROI). 

Therefore, farms and agribusinesses ought to ensure that their precooling systems are of a good standard. There are a variety of solutions within the ecosystem that could fit fresh produce traders of all sizes and produce. But it is crucial to get the right technology solution that offers the required settings for the specific product needs at each stage along the cold chain.  Farmers, agribusinesses and traders, especially in emerging economies, often make the wrong choice while determining cooling solutions for their postharvest operations. Aspects such as price comparison, duration of delivery, weak overall knowledge of proper cold chain practices, and a limited number of trained cooling technicians are often driving sub-optimal choices on cooling solutions. For this reason, many farms and agribusinesses , requiring precooling tend to put up adaptations of old cooling structures or buy unfitting solutions such as using reefer containers to start the cooling process.

Risks related to the lack of, or inefficient pre-cooling

Pre-cooling is the process of treating fresh fruit and vegetables with overpressure airflow (or in certain cases cold water) to remove the field heat and slow down the respiration (that generates heat), before grading, packing, potentially processing and either storing or shipping. This technique has a positive effect on the shelf life and quality, compared to non-pre-cooled products. Air-cooled (without overpressure) cold storages and reefer containers are built primarily to maintain the temperature of the products and in most cases lack the features needed to cool down the core of a pallet of a fruit. Therefore, products should always be pre-cooled to a specific temperature, before being loaded into a reefer container or a refrigerated truck. Not carrying out this process properly generates condensation with high risk of mold growth, shrinkage, aesthetic defects (spots, discoloration, browning, among others.) 

The condition of products before they are loaded into reefers plays an important role in their condition upon arrival. That is why all products must be treated correctly before this. Even though the temperature, ventilation and humidity are all optimal during the entire voyage, products will only arrive in perfect condition if the pre-loading treatment is performed correctly, and for this, you must invest in proper pre-cooling and cooling solutions.

Reasons why the usage or adaptation of reefer containers for pre-cooling is not convenient

  • Longer time to optimal temperature: a reefer is designed to maintain the pre-cooled cargo temperature but cannot extract the field heat in a sufficiently short time and does not have enough air pressure to get to the core of a pallet. Its cooling equipment offers a normal speed airflow at a pre-established temperature, that goes vertically bottom-up. Having a “slow” and not forced airflow means the field heat inside the pulp will take a longer time to bring down, which affects quality by an accelerated deterioration and senescence processes.  
  • High condensation rates: risk of high condensations rates, that occurs when hot, humid air touches colder surfaces. Cold chain design is fundamental to avoid condensation that can contribute to the spread of diseases, bacteria and fungi and yeast. 
  • Higher energy consumption: the great majority of brand-new reefers are less energy efficient compared to cold in-field rooms at positive temperatures. In other words, energy use in a shipping container is affected by the amount of heat the refrigeration equipment must remove. Additionally, a reefer container can be more susceptible to heat loss, via transmission through walls, air leakage and evaporator coil fans. 
  • Temperatures and damages to crops: In addition, many agribusiness and refrigeration technicians set below zero evaporating temperatures on used reefers, with the expectation that lower temperatures would generate better cooling, while, in most cases, this is severely damaging the crops 
  • Not expandable: As a rule, reefer containers are available with lengths of 10′ (3M), 20′ (6M) and 40′ (12M) – just like shipping containers. The measurements are the same as for shipping containers and each generally has a fixed capacity on the number of pallets that can fit in. The reefer structures are sturdy, with inner walls and floors made of stainless steel, covered with about 100mm of polyurethane isolation. For this reason, agribusinesses with increased production must buy additional reefer instead of being able to expand a cold room’s structure.

Key features to look out for in a pre-cooling solution

Agribusinesses, especially small-scale, can choose from various options when it comes to cooling systems. The selection should start with the pre-cooling system, considering the efficacy, efficiency, and safety of the type of product to be cooled and the expected financial profits. As well one should consider not only the immediate needs but selecting the solution that better fits the future expectations of growth. In this sense, systems that offer higher energy efficiency, modularity for easy expansion and remote monitoring should be prioritised regardless of the price difference with other systems such as reefer containers.

For the past ten years, InspiraFarms has designed and installed over 100 facilities with pre-cooling features, including blast chillers for forced air pre-cooling, to facilitate the rapid removal of field heat, shortly after the harvest. This way, cooling is highly efficient from the initial point post-harvest. Additionally, while putting up a cooling facility, InspiraFarms gives you multiple options on size – depending on factors such as production volumes per week (up to a capacity of 1,000 pallets) and best cooling co-efficiency. Unlike reefers, the design and cooling systems are also sized to the needs of users, and add-ons, such as humidifiers, ethylene sensors, remote monitoring, and alarm systems, among others can be customised to help tailor whichever cooling produce needs.

Reefer containers are the best possible option for long-distance transportation of already chilled or frozen products, whilst being among the worst possible ones to pre-cool fruit and vegetables after the harvest, second only to not having any cooling.

Interested in on-farm pre-cooling and cold chain for your fresh produce? 

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