Jujube drying process
The core of jujube processing is drying. The drying process of jujube is complete internal water evaporation and sugar conversion on the premise of preserving the original quality of the jujube as much as possible. Red jujube is rich in sugar, and the polysaccharide contained in them is a substance without sweetness. It must be converted into monosaccharides under the action of biological enzymes before it can be sweetened. This is the reason why red jujubes become sweet after ripening. It is necessary to fully convert the sugar in red jujubes under the action of biological enzymes, and it is necessary to enhance the activity of biological enzymes. Through long-term practice, we found the best temperature range for sugar conversion in red jujubes, that is around 60°C.
1 heating stage
During the drying process, if the jujube fruit directly enters a high temperature environment suitable for sugar conversion, the huge temperature difference will cause the jujube to undergo a biological protection reaction, the pores of the epidermal cells will shrink, the crust will harden, and the water inside the jujube will be prevented from evaporating. Therefore, in the early stage of drying red dates, it is necessary to fully preheat and gradually heat up to prepare for a large amount of water evaporation. Keep it at 45°C for 2-3 hours. When the temperature of the jujube reaches 45°C, it will be slightly hot. After 2-3 hours, wrinkles will appear on the body of the jujube when the jujube is pressed hard; A small layer of water droplets will appear.
2 drying stages
To make the free water in the jujube evaporate a lot, the temperature must be increased at this time, and the drying room should reach 65 ℃ within 3-5 hours. The temperature should not exceed 70 ℃. In order to facilitate the evaporation of a large amount of water, pay attention to dehumidification process and keep the indoor temperature from changing greatly, so as to continuously evaporate the water. When there are wrinkles on the surface of the jujube fruit, it means that the drying process is normal.
3 Dehumidification stage
When the temperature in the jujube is uniform, the work at this stage can be completed within 6 hours. As the water in the jujube is low in the later stage, it is important to control the temperature. The preferable temperature is 50 °C. At this time, if the humidity content is higher than 60%, it can be slightly dehumidified. As the moisture in the jujube gradually balances, the purpose of drying is achieved. Afterwards, you can unload the dried samples in time.
4 cool down
The ventilation and heat dissipation performance should be conduct before cooling down. The red jujubes which are unloaded from the drying room cannot be stacked immediately in the warehouse. The red jujubes themselves contain a lot of sugar, under the action of heat, the sugar is easily fermented and deteriorated, the original pectin in the jujubes will also be decomposed into pectin and pectic acid. if store the red jujube without cool down, it will inevitably make the jujube a mess, and will also change the sugar content in the jujube, which will destroy the quality of the red jujubes. Therefore, after the drying process, it must be completely cooled down before storing the red jujubes.
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