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How to do precooling while the temperature difference is huge for the fruit and vegetable to enter the cold storage
Feb 24, 2018

After harvest of fruit and vegetable, the precooling is important, which is a procedure to remove field heat quickly by using a set of equipment and technology, and cool the products till appropriate temperature for transport and storage and keep various quality levels for hardness, freshness etc and prolong the storage period and decrease energy usage of refrigeration machinery. And prevent frost for those packed in plastic film.

    The cold chain technology is mature and widely used in developed countries, ensuring timely precooling for product freshness. In China, there are not specific precooling facilities for most storage, and often use fast moving into cold storage and precooling in the storage.


    (1) Cold storage precooling

  Newly picked and sorted and packed fruit and vegetable are put into the cold storage quickly, make ventilation holes in the packing crate, and leave half open of the packing bag. Clearance left while stacking or put them directly on shelves(for example: garlic shoot), start the refrigeration machiney and use air cooler to bring away the heat and cool the products down.  The air flow speed between stacks should be about 0.3-0.5m/s. when the products reach required temperature, move to the other cold storage or stay in but close bag and stack accordingly.  It takes time slowly, usually about 1-3 day to cool to required temperature, and to prevent dehydration, put some water to the ground is necessary.

    (2)Forced Air Pre-cooling

    The standard forced-air pre-cooling is realized by specific equipment, firstly arrange the crates in order with good ventilation ensuring each row of crates has enough air flow. The forced-air pre-cooling machine can be installed with a wheel to move freely in the cold storage. This method is quick, it only takes 5-7 hours to decrease fruit temperature from 30℃ to 5℃ and applicable for various fruits and vegetables.

    (3)Cold water precooling

    Soak the fruit crate in cold water or sprinkling , this is usually made into tunnel type and transferred by conveyor belt or move by water. In some case, the sprinking water in the tunnel is about 0-1℃ and move 25-30 minutes on the tunnel conveyor belt, the fruit temperature can be decreased from 30℃ to 5℃. this method is applicable for carrot, peach, sweet corn, beans etc..

    (4)Nature precooling

    Nature precooling is simple, put the harvested crop in ventilated place away from sunshine and drive the field heat naturally.  If there are no other better precooling method, the nature precooling can be used as a plan B.

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