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Shandong Fangyuan Huizhong Intelligent Equipment Co., Ltd. is a specialized manufacturer of food machinery that integrates R&D, production, and sales. The company boasts a strong technical R&D team, a professional production management team, and an outstanding sales and after-sales service team, offering first-class services and robust capabilities.
30
2024
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04
Walnut Kernel Drying and Processing Technology
Author:
Walnuts begin to ripen from late August to early September.
1. Processing Green Husks: Walnuts gradually enter the ripening stage from late August to early September. At this time, the husk color changes from dark green to yellowish-green or pale yellow, and some of the involucres begin to split open. A small number of fallen nuts can already be harvested for processing. It’s important to note that green-husk walnuts should not be exposed to direct sunlight—once dried in the sun, the outer husk becomes difficult to remove. Therefore, the walnuts should be piled in a cool, shaded area or indoors, with the pile height kept between 30 and 50 centimeters and covered with walnut leaves or straw. After 3 to 5 days, once the green husk has naturally separated from the shell, gently peel it off by hand or carefully cut it open with a small knife. Typically, 4.5 kilograms of green-husk walnuts can yield 1 kilogram of dried walnuts.
2. Cleaning and Drying: After removing the shells, promptly rinse the walnuts with clean water. If left for too long, the vascular bundles at the bottom of the walnuts will shrink, allowing cleaning water to easily seep into the shell, causing the kernels to discolor and even rot. Place the walnuts in a basket, then immerse them in water and use a bamboo broom to stir and wash them thoroughly for 5 minutes each time, repeating this process and changing the water 2 to 3 times.
3. Kernel Extraction: When manually extracting kernels, place the walnuts with the seam facing downward and tap them evenly—avoid applying excessive force or repeating the process too many times. Typically, about 38 kilograms of kernels can be extracted from every 100 kilograms of walnuts. Walnut kernel dryer.
4. Soaking in the Spice Solution: Mix together 20% doupí, 5% cloves, 25% fennel, 20% licorice, 15% star anise, 10% pepper, and 5% cinnamon sticks. Then add 10 times the volume of water, bring to a boil, and maintain at boiling temperature for 30 minutes. Afterward, filter out the extract. Add 2% to 5% edible salt and 0.03% to 0.05% sodium glutamate to the extract. Soak walnuts in the spice solution prepared as described above for 1 hour, then remove and drain thoroughly for later use.
5. Drying using a heat pump dryer: The walnut kernels are placed into specially designed 304 stainless steel mesh trays, with each tray holding 15 kilograms. Each vehicle carries 12 trays. The equipment used is an Obert 7P closed-loop dehumidifying heat pump dryer, which can accommodate up to 8 material carts at a time, with a single feeding capacity of up to 1,200 kilograms. The drying time is controlled between 15 and 20 hours. The system consumes approximately 7 kilowatt-hours of electricity per hour. After soaking, the walnut kernels are continuously dried at a temperature ranging from 60°C to 70°C until their moisture content is reduced to below 10%.
6. Adding the Sugar Coating: Add 20–30 liters of water to the double boiler, then add 60 kg of beet sugar, 30 kg of glucose, and 10 kg of high-fructose corn syrup. Stir thoroughly and heat until boiling. Once all the sugars have completely dissolved, add 100–200 grams of citric acid. While the mixture is still hot, pour the roasted walnuts into the sugar syrup and mix thoroughly until evenly coated. After removing from the pot, continue drying at a temperature of 60–80°C.
7. Drying and Packaging of Walnut Kernels: In a dry and hygienic indoor environment, walnut kernels that have been dried using a heat pump dryer and coated with sugar syrup are packed into aluminum foil composite bags. The bags are then sealed using a vacuum packaging machine or subjected to nitrogen packaging, thereby completing the product.
A practitioner of microwave-magnetic heat pump, hot-air solar energy, and energy-saving integration, dedicated to promoting microwave-composite heat pump drying technology, advancing the comprehensive application of solar thermal pumps, developing microwave-hot-air composite drying systems, as well as multi-layer continuous drying equipment and mesh-belt tunnel-type drying facilities.
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