(1) natural drying
It is a natural drying method of dried jujube by sunlight. This method is undoubtedly an energy-saving method, which can better maintain the original excellent quality of jujube fruit, with simple equipment and easy operation. The shortcomings are that the jujube fruit is polluted during drying, which is not conducive to the production of pollution-free jujube, and it is easy to cause a large number of rotten fruits in rainy days, and the benefits are reduced. Methods: A spacious and shady yard was selected as threshing ground. Bricks and stalks were used for paving, with a spacing of 30 cm and a height of about 20 cm. Bamboo foil or reed mat was laid on it, and jujube was spread on the bamboo foil and reed mat with a thickness of 6 ~10 cm, with 30 ~ 50 kg of jujube per square meter. Turn it up and down every 1 hour or so during the day to make the jujube dry evenly. At night, jujube is concentrated in the middle of foil, covered with mat or plastic film to prevent dewing and moisture regain. After sunrise the next day, spread it out and continue to dry. After10 ~ 20 days, the jujube will not feel soft when held by hand. When the water content of jujube falls below 28% and the jujube falls below 25%, it can be packaged and transported abroad or stored in stages. The drying time of jujube is related to the maturity and weather of jujube, so the moisture content of jujube should be detected frequently. Jujube is not resistant to storage, and low moisture content affects the taste and appearance, which affects the sales in the market. In case of rainy weather after jujube harvest, we can try to scald jujube fruit in boiling water for 30 seconds at medium speed and then spread it in layers in the idle room, and then move it out of the house to continue drying in sunny weather, which can reduce rotten fruit. According to the author's experiment, there is basically no rotten fruit in the drying of boiled dates, and the rotten fruit rate of blanched dates is over 24%. In addition, jujube can also be temporarily stored in the cold storage, with the storage temperature controlled at about 0℃, and then taken out to dry after sunny days, which can greatly reduce rotten fruits.
(2) Manual drying
Also known as drying method. Drying jujube is not affected by the weather, with short drying time, high drying rate, less loss of nutrients, more vitamin с preserved in the finished product, clean jujube fruit without impurities and high commodity rate. It can also effectively reduce the loss of rotten fruit in rainy days. In areas where there are many autumn rains, manual drying should be the main method, and large jujube processing enterprises should adopt manual drying to produce pollution-free dried dates. There are two kinds of drying rooms commonly used for manual drying: flue type and steam type. The size of the drying room is built according to the needs. The fuel (coal) used in the flue drying room is heated and baked through the flue; Steam-type drying room is the baking of boiler steam through pipes and radiators. The baking procedure is as follows:
① Cleaning, grading and tray-loading: after cleaning, the jujube fruits are tray-loaded according to their size and maturity, and the thickness is suitable for overlapping two dates.
(2) baking: the first 6 hours is a slow heating stage, from normal temperature to 55℃; After 6 ~ 8 hours, it is a rapid heating stage, and the temperature is controlled at 65℃. At this time, attention should be paid to moisture removal, and the dates should be turned in time to prevent stuffy dates, which lasts for 20 hours; From 20 to 22 hours, the temperature of drying room rises to 68 ~ 70℃ for the high temperature stage, which accelerates the discharge of water in pulp; Press the fire control temperature for 22 ~ 24 hours, and leave the drying room when the temperature slowly drops to about 40℃. At this time, the moisture content of the dried jujube is still about 30%, and it can be dried for 3 ~ 4 days after sunrise. When the moisture content of the jujube drops below 28%, it can be packaged, transported or stored. This is better than the color of jujube dried once. In the production of green food, the baking time should be appropriately extended. When the moisture content of jujube is reduced to 28% and jujube is reduced to 25%, it will be taken out of the drying room, ventilated and cooled, and then aseptic packaging will be carried out. Different varieties of jujube have different maturity, and the baking temperature and time at each stage are different. We should master the appropriate temperature and time in practice, and the temperature and time provided above are for reference only.