Red jujube, also known as Chinese jujube and rubber jujube, is a unique fruit in my country and is the fruit of the jujube plant of the rhamnaceae family. It has been cultivated in China for more than 4,000 years and is known as the "King of Fruits". Red dates contain cyclic adenosine monophosphate, polysaccharides, flavonoids, triterpenoids and other functional components, which have certain health care functions. Chinese traditional medicine believes that red dates are sweet and warm in nature, and they belong to the spleen and stomach meridians. Modern medical research shows that red dates can enhance immunity, anti-oxidation, anti-allergy, lower blood pressure and blood lipids, improve liver function, delay aging, calm the nerves, inhibit the growth of cancer cells, and prevent cardiovascular and cerebrovascular diseases.

Due to the high water content of fresh jujube, it is not easy to store and transport under natural conditions, so most of them are stored by drying. On this basis, in order to increase the added value of products, researchers pay more and more attention to the deep processing of red dates. As a new type of dried product, jujube powder has low moisture content, which can effectively prolong the storage period; high utilization rate of raw materials, and is not limited by the shape and size of jujube; easy to eat, and can also be added to other foods to improve its nutritional quality. Therefore, the development and application prospects of red jujube powder are very broad.

1.1 Drying technology of red jujube slices

The hot air drying technology is to combine the heat source equipment with the fan, so that there is a certain temperature difference between the red dates and the surrounding environment. Research by Zhao Huanxia and others showed that hot air drying is a drying technology with the highest utilization rate and the strongest applicability in the drying process of red dates. However, there are problems of high temperature and long time. In this process, heat-sensitive substances are seriously lost, the aroma of jujube is replaced by burnt bitterness, and the Maillard reaction is obvious. However, the technology is mature, easy to operate, not affected by the environment, and suitable for large-scale production.

The main advantages of microwave drying technology are short time consumption, uniform temperature distribution, high drying rate, and sterilization effect, but high energy consumption and high investment. In the process of exploring the effect of different drying methods on the properties of red jujube slices, it was found that the products after intermittent microwave drying The quality is better than that after continuous microwave drying, mainly because intermittent microwave drying can make red jujube slices avoid the consequences of excessive oxidation or degradation of nutrients due to concentrated heating.

Combined drying technology is because a single drying technology has its limitations when drying materials. By analyzing the properties of materials, researchers combine two or more drying technologies, and perform them in stages or at the same time to achieve the advantages between technologies. Complementary. Taking the red jujube tablets prepared at different drying temperatures as the research target, the quality indexes of the red jujube tablets after combined drying with hot air and medium and short wave infrared were determined. The results show that the product quality of combined drying is much higher than that of single drying method, and the drying time is reduced to 1/3 of that of hot air drying. Using the self-designed hot air microwave coupling dryer to dry fresh jujube, it was found that high-quality products with more vitamin C content, better rehydration and higher efficiency than the single drying method can be obtained.