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Wolfberry has a planting history of more than 4,000 years and is a unique fruit variety in China. It has been planted in large areas in Xinjiang, Gansu and Ningxia. Wolfberry is rich in carotene, vitamin B, C, P and trace elements such as phosphorus, potassium, calcium and magnesium. It has the reputation of vitamin pills. According to the authoritative department, Wolfberry has a sugar content of more than 55%, a crude protein content of about 3%, a phosphorus content of 0.1% to 1.3%, and a potassium content of 0.6% to 1.1%. Contains 87g of vitamin C per kilogram of Wolfberry,1.7 g of vitamin B1. It can be seen that Wolfberry is rich in nutrients, but it has a fatal weakness of “easy to smash”, which makes it difficult for long-term preservation of fresh Wolfberry. Therefore, the drying treatment of Wolfberry is particularly important, and its drying technology is even more important. The most important part of the entire processing process.
1. Traditional Wolfberry drying method
At present, Wolfberry's drying methods are mainly divided into natural drying method and artificial technology drying method. Natural drying mainly refers to relying on the sun to dry Wolfberry or naturally drying Wolfberry, which is the most traditional drying method. The quality of Wolfberry dried using this method is completely dependent on weather and ventilation, and the quality of Wolfberry cannot be guaranteed. The Wolfberry harvest season is mostly concentrated in August to October. This season is mainly rainy weather, and the ventilation is slightly bad. Wolfberry is prone to mildew. In addition, natural drying takes a long time, usually about 30 to 40 days, which also affects the listing time of Wolfberry, which in turn affects the economic income of the farmers. Artificial technology drying method refers to the method of using artificial heat source to generate hot air or radiation heat transfer to make Wolfberry dry quickly. This drying method can save time and effort, improve the yield and quality of Wolfberry products, and has obvious economic benefits. In China, the main artificial drying techniques applied in Wolfberry processing are as follows: hot air drying technology, infrared drying technology, radio frequency hot air combined drying technology, freeze drying technology and microwave vacuum drying technology. Among them, microwave vacuum drying technology is a high-tech, combining the advantages of microwave drying and vacuum drying, suitable for drying agricultural and sideline products, especially Wolfberry.
From the mechanism of microwave vacuum drying, the higher the degree of vacuum, the lower the boiling point temperature of the moisture contained in the wet Wolfberry, and the easier it is to vaporize and escape, so that the Wolfberry is dried. During vacuum drying, when the vacuum is increased to a relatively low boiling point, the moisture in the Wolfberry is rapidly and rapidly vaporized. The lowering of the boiling temperature of the water increases the driving force of the moisture inside and outside the wet Wolfberry, accelerates the movement of moisture from the interior of the Wolfberry to the surface and the diffusion from the surface to the surrounding air, thereby accelerating the drying process. However, due to vacuum drying, the dehydration of Wolfberry relies on heat conduction for heat transfer. In the case of low pressure, the heat transfer by this convection method is too slow, and the advantage of vacuum drying is not fully exerted. Microwaves (electromagnetic waves with a frequency of 300 MHz to 300 GHz and a wavelength of 1 mm to 1 m) can generate high-frequency electromagnetic fields, and high-frequency electromagnetic oscillations can trigger the movement of water molecules, which causes the Wolfberry to heat up rapidly. This is the microwave directly on the Wolfberry. Heating, heat transfer faster. It can be seen that the microwave can provide a heat source for vacuum drying, effectively solving the problem of the conventional heat conduction rate under vacuum, shortening the drying time and improving the production efficiency. Microwave drying has the advantages of fast heating speed, short drying time, good selectivity, high energy efficiency and easy control. However, simply drying the Wolfberry with microwaves will cause the glassberry to be scorched due to excessive temperature. If the vacuum drying technology is used during microwave heating, the evaporation temperature of the water can be lowered, the moisture in the Wolfberry can be quickly evaporated at a lower temperature, and the oxidation can be avoided, thereby protecting the quality of the Wolfberry. Therefore, combining microwave drying and vacuum drying technology to give full play to their respective advantages, the Wolfberry can be dried at a relatively low temperature, which not only maintains the nutritional content of Wolfberry, but also guarantees the finished product quality of Wolfberry and accelerates the dryness. Increased economic efficiency.
3 application prospects
Microwave vacuum drying equipment is a new combined drying machine developed with microwave drying technology and vacuum drying technology. It is an organic combination of microwave drying technology and vacuum drying technology. The machine combines the advantages of both and overcomes the two. Disadvantages, improve the nutrients of dry materials and improve the quality of drying. It is characterized by uniform drying and short cycle, which can maintain the nutritional composition and inherent flavor of Wolfberry, and also has the functions of anti-mildew, sterilization and preservation. At the same time, it is energy-saving and environmentally friendly, convenient for control and continuous production.See the news list>>