Study On Hot Air Drying Process And Technology Of Red Jujube

Red jujube is favored by people because of its nutritional value,and its end-product can be found everywhere in our daily life.Most of the fresh jujube must be dried after harvest,to achieve the required safe moisture content before storage,because fresh jujube is very difficult to store.Natural air drying is the traditional drying method of red jujube.It's yield is not high,could be influenced by environment factors,and the time of drying is also longer,which can't meet the dry demand of red jujube.While the traditional drying system has a large amount of dry production and high energy consumption,and it will bring environmental pollution,which does not meet the national policy requirements for energy conservation and emission reduction.Emerging artificial drying technology has hot air drying,microwave drying,vacuum freeze dried dates,solar drying and far-infrared drying,hot air drying is the most feasible for red jujube drying by discussing the advantages and disadvantages of each type of drying technology.Set up a small hot air drying laboratory bench that could carry out many kinds of circulation system and air supply method which based on the similarity.Develop the hot air drying process that according to the traditional drying process of red jujube,and the experimental study on the hot air drying process of the winter jujube was carried out.Preheating stage: the initial temperature starts at 30 and heats up at 5 per hour to 65? ? ?.Evaporation stage: keep the temperature of 65 for 12 hours.Drying stage: coll to 55 to ? ?continue drying until the moisture content of jujube reaches the requirement.It is found that the increase of wind speed can improve the drying rate of evaporation stage that could reduce the total drying time and improve the drying efficiency.The relative humidity in the preheating stage has an effect on the drying time in the contrast test of the whole and sliced jujube.It is verified that increase relative humidity in preheating stage can reduce drying time,improve drying efficiency and make skin color more bright by three groups single factor experiment of relative humidity(40%,50%,60%)in preheating stage.The drying effect is the best and the drying time is the shortest when the wind speed is 1.2m/s and the relative humidity is 60%.Increase the relative humidity in the preheating stage can reduce the sclerosis crusting of skin,and internal moisture is easier to come out in the evaporation stage.So,the drying efficiency is raised,the degree of shrinkage is more uniform and the probability of bad jujube is reduced.