Trehalose is not easy to dissolve. Trehalose is an insoluble sugar. A certain amount of water needs to be added in the boiling process, and then heated to a certain temperature to dissolve it. When the temperature of the syrup gradually rises, the water gradually evaporates, and the concentration of the syrup gradually rises, trehalose molecules in the syrup begin to gather together to form crystals, which leads to the syrup gradually becoming sticky and finally solidifying. In addition, too long heating time or too high temperature during sugar boiling can also lead to the solidification of trehalose syrup.