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Drying of red jujube by drying technology

red jujube drying1

Red jujube is a unique fruit tree variety in China, which has been cultivated for more than 4000 years. 90% of the output of red jujube in the world comes from China.

Red jujube varieties are mainly: grey jujube, Jun jujube, Jinsi jujube, winter jujube. In the same varieties also generally divided into 5 to 6 grades, so as to determine the price. Concentrated areas of Chinese jujube production and processing: Hebei Cangzhou, Henan, Zhengzhou, Leling, Shandong, Shanxi, Guangzhou, Hunan and most areas of Xinjiang. Due to the changing climate and soil conditions, many of the areas mentioned above are not suitable for jujube growth. However, due to historical reasons, these places, which used to be rich in high-quality jujube products, have now become large-scale distribution centers of Chinese jujube, except for a small amount of production, and almost all jujube are from Xinjiang.

Xinjiang is now the most suitable area and region for red jujube cultivation throughout the country and even in the world. Because of Xinjiang’s unique geographical advantages and conditions, is the mainland and other regions can not compare. Because Xinjiang is the topographic feature of “three mountains and two basins”, the edge of the basin is Gobi, the middle of the basin is desert, far away from the ocean, and there are alpine barriers. This formed Xinjiang temperate, warm temperate inland arid climate characteristics: first, the temperature difference between spring and autumn, the second is less precipitation, the third is the sunshine is very adequate, the fourth is dry climate, and the fifth is rich in land resources. These advantages have formed the unique quality of Xinjiang red jujube, Xinjiang red jujube, in sugar content, soluble solid form The quality of VC and is higher than that of the same variety in the mainland, and the taste is better than that of the same variety in the mainland, which can not be compared with Xinjiang red jujube in the quality aspect of the hinterland red jujube.

Red jujube is a traditional Chinese health food, rich in nutrients. In addition to some fresh eating, most red jujube are consumed directly in the consumer end market as dry and clean fruit products; in addition, the region of red jujube production is relatively concentrated, and the harvest is concentrated in the autumn harvest period and the consumption market is facing the whole country. To facilitate storage, transportation and sale, red dates need to be cleaned, dried, cooled, softened and pasteurized.

The red jujube contains abundant dietary fiber and sugar, different natural climate, soil and water, sunshine conditions, growth cycle of red jujube itself, nutrient acquisition and so on, together determine the quality of red jujube. The criteria for identifying the quality of jujube refer to its shape, taste and color. High-quality jujube contains rich dietary fiber and sugar, full and elastic fruit shape, sweet taste, red and bright color.

The processing of red jujube has two methods: natural drying and artificial drying:

Natural drying: due to the long time and many uncertain factors, it needs a large number of manual flip, dried product color is also uneven, not suitable for large-scale operation.

Artificial drying: there are many methods, more traditional is suitable for coal combustion heat for drying. In the past two years, air pollution has been serious, environmental protection departments have been heavily supervised, and coal fired boilers have been banned in many places. At the same time, coal combustion process will produce a large number of sulfides, food processing will also produce secondary pollution. After that, drying with coal is no longer the best choice. The following mainly introduces the application of dryer in drying red jujube.

red jujube drying2

Drying is the core of red jujube processing. The drying of red jujube is the process of moisture evaporation and sugar transformation under the premise of preserving the original quality of red jujube as much as possible. Red jujube contains abundant sugar, which contains polysaccharide is a kind of substance without sweet taste, must be transformed into monosaccharide under the action of biological enzyme, this is the reason why the red jujube becomes sweet after ripening. We need to make the sugar in red jujube fully transformed under the action of biological enzymes, we need to enhance the activity of biological enzymes. Through long-term practice, we have found the optimum temperature of sugar conversion of red jujube at about 60 degrees.

Temperature rise stage

During the drying process, if the red jujube fruit directly enters the high temperature environment suitable for sugar transformation, the huge geothermal difference causes the red jujube to have the biological protection reaction, the epidermal cell hole shrinks, the crust hardens, prevents the red jujube internal water evaporation. Therefore, in the early drying period of red jujube need to be fully preheated, gradually heating, for a large amount of water evaporation preparation .45 ℃ to maintain 2 hours, when the red jujube temperature of 45 ℃, a little hot hand, waiting for 2- 3 hours, when the red jujube body will be forced to wrinkle; When the temperature of red jujube reaches 45 ~ 48 ℃, a layer of water droplets will appear on the surface of red jujube.

Drying stage

When the free water in red jujube was evaporated, the temperature must be raised to 65 ℃ in the drying room within 3-5 hours, but not more than 70 ℃. In order to keep the indoor temperature constant, the moisture should be evaporated in large quantities and dehumidified. When the surface of red jujube fruit wrinkles, dry normal.

Dehumidification stage

When the internal temperature of red jujube is uniform, this stage can be completed within 6 hours. Because the red jujube moisture is not much, we should pay special attention to temperature control, do not oversize, 50 ℃ is the best. At this time the relative humidity also fell down, such as above 60 cents can be slightly dehumidified. As the moisture in the red jujube gradually balanced, it also reached the purpose of drying. Take care to unload the dry samples in time.

Cool off

Dried red jujube must pay attention to ventilation and heat dissipation, wait for cooling before piling up. If the jujube, which had just been unloaded from the oven, was stacked in the storehouse, because the red jujube itself contained so much sugar, the sugar would easily ferment and deteriorate under the action of heat, and the raw pectin in the red jujube would also be decomposed into pectin and pectin acid, which would inevitably make the red jujube a mud stall. Also can make the red jujube sugar change, appear with sour silk, so that the red jujube is destroyed. Therefore, after drying, must be thoroughly cooled before it can be stored.

Now the drying equipment has solved the quality and efficiency of red jujube drying, aiming to reduce more energy consumption and save more cost.

red jujube drying3

note: different varieties, different sizes, different regions, different moisture content of red jujube drying process will be slightly different. The above summary is aimed at the technology of ash jujube.

Post time: Aug-07-2019