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Fresh-keeping methods of grapes in cold storage
Mar 05, 2018

    Haocool is a professional cold storage design/build company and in this article HaoCool would like to share the fresh-keeping methods and solve growers` cold storage problems and decrease loss rates.

    Fresh-keeping technics of grapes in cold storage

    1. it depends of kinds of grapes, different kind has different characteristics. Hard fruit is easier stored compared with soft ones. The bigger ones with thicker peel is easier stored compared with smaller ones.

    2. harvest conditions

    Good harvest time had better in shiny morning after dew is disappering. If encounter rain or watering, postpone 5-10days. The grapes to be stored in cold storage shall be in good quality and conditions, keeping away those with disease, injury, bad-shape. Should spray bactericide.


    What grapes are not allowed to be in cold storage:

    1. not mature,

    2. Water saturated,

    3. With disease, bugs.

    4.  Rotten, green, size unconformity.

    5. Those affected by natural disasters.

    3. cold storage conditions

    Before put into cold storage, disinfection treatment should be done in advance. Generally 5‰ potassium permanganate to be applied 7 days before, and Fumigation with sulfur 3 days before entering.

    4. pre-cooling before entering cold storage

    During harvest, use 20kg standard crate, put in the shade till evening to be tranferred to cold storage for pre cooling till -1℃. quick precooling can decrease the respiration and release of ethylene fastly. Jufeng kind of grapes precooling time should be around 12 hours, too much longer time will lead to dehydration and falling apart. Small package of fresh-keeping bag shall be open when entering, to remove the field heat and moisture, after precooling the bags can be sealed.


    5. stacking and fresh-keeping

    The precooled grapes can be stacked every 3 tons(namely 150 crates), put 10 bags of fresh-keeping agent in the middle of crates and put 2 fresh-keeping papers above. Seal the whole stack with plastic film to make each stack a whole but separate entity. And in this small environment, the fresh-keeping gas release by fresh-keeping agent are inside. The big space can act as buffer zone to let grapes away from drug effect. Because isolation from outside, the carbion dioxide and moisture by respiration fills the environment inside the plastic film, can further dampen the respiration and result in a reasonable respiration. Because the respiration heat, the film inside temperature is higher than outside, most of the water vapor released condenses on the inner wall of the plastic film to become ice instead of being attached to the surface of the fruit,  the grapes is still clean, without injury and less prone to bacteria. Relative humidity inside the film can be well maintened thus decrease the loss of grapes water content and prolong the storage time.

    6. management during storage

    1. when grapes are all put inside cold storage, put small quantity of sulfur between stacks and set fire and fumigate in order to kill bateria brought by humans. Because the cold storage controlles temperature automatically, the managing personel had better not go inside. Keep inside temperature -2 till 0 ℃, the difference between inside and outside film can be 1 ℃.

    2. when the gas and cold storage temperature get steady and normal, conduct ventilation once and then sulfur fumigate once and close storage door.

    3. after entering for 2 months, check grapes conditions and change gas and replace the fresh-keeping papers without moving grapes then stack and film wrapping.

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