Storing watermelons properly can significantly extend their freshness and quality. One effective method involves using sand traps. After 40–50 days of storage, the watermelon can still maintain its color, aroma, taste, and nutritional value. The process begins by selecting a well-ventilated and light-filled house. Clean the area and spread a 70-centimeter layer of fine river sand as the base. Harvest seven mature watermelons on a sunny or cloudy evening, ensuring they are well-shaped, undamaged, and free from pests. Cut the vines about 33 centimeters from the ends and immediately cover the cut with hay ash to prevent bacterial infection. Leave one green leaf on each vine and place the watermelon on the sand bed, covering it with 5 cm of fine sand. Expose three leaves outside the sand. Handle the watermelons gently to avoid damaging the rind. Only one layer of watermelon should be placed in the sand bed to prevent crushing. Every 10 days, apply 50 kg of monobasic potassium phosphate mixed with 50 kg of water as a foliar spray to keep the leaves healthy. When the sand surface turns white, mist it with water to increase humidity. It's best to store and transport watermelons on the same day they are harvested.
Another method is ozone preservation. Select robust, well-shaped, disease-free watermelons, cut the vines, and handle them carefully during transport to avoid damage. Store them in a disinfected cellar, placing them on soft straw mats to avoid direct contact with the ground or plastic. Cover them with a soft straw bag to protect against dust and moisture. Maintain a temperature of around 4°C, as higher temperatures may speed up respiration, while below 3°C can cause freezing. Monitor temperature changes and adjust the thermal layer accordingly. Keep humidity at 85% and ensure proper oxygen exchange. Apply 20 grams of ozone daily for 150 kg of watermelon, with a 10-gram dose every 15 minutes every 12 hours. Every five days, wear clean gloves to turn the watermelons and remove any that show signs of disease. Avoid storing other fruits or vegetables alongside watermelons in the same cellar.
For available storage, choose a cool, ventilated, empty house and disinfect it using a 40% formalin solution diluted 150–200 times. Apply a copper sulfate solution (6%) to the stalks and skins of the watermelons to prevent bacterial infections. Lay a layer of sterile reeds on the floor, then place the watermelons in a single layer. Close the doors and windows during the day and open them at night to regulate temperature. Maintain a room temperature of 15–16°C and 80% humidity. Mist the ground when dry. This method allows for up to one month of storage, preserving the watermelon’s freshness and quality similar to newly harvested ones.
Cellar storage is another effective option. Choose a dry, solid soil location and dig a small cellar shaped like a gourd, approximately 3 meters deep. Line the bottom with a 1 cm thick layer of fine sand, and sterilize the area with 200 times diluted oxidative music or 150–200 times diluted formalin. Cool the watermelons before placing them in the cellar, arranging them in their original growth position with space for inspection. Keep the cellar entrance about 1 meter square and slightly above ground level for shade support. Maintain a temperature of around 15°C and carbon dioxide concentration between 2% and 4%. With this method, watermelons can remain fresh for up to three months.
Silicone rubber film bags offer an innovative storage solution. These are closed bags made from 0.15–0.18 mm thick polyethylene film with a silicone rubber gas exchange window. They allow controlled permeability of oxygen and carbon dioxide, enabling automatic regulation of internal conditions. By adjusting the size of the silicon window, different varieties and ripeness levels of watermelons can be safely stored. This method simplifies management, increases storage capacity, and reduces costs.
Lastly, salt water preservation is a traditional technique. Select medium-sized, mature watermelons and soak them in 15% salt water. Dry them thoroughly and seal them in polyethylene bags, placing them in a cellar or wooden container. This method keeps the watermelon skin fresh and tender even after a year, maintaining its sweetness and flavor. It is also effective for preserving grapes, cucumbers, and apples.
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