Study on the Changing Rule of the Dielectric Properties of the Damaged Red Jujube in the Drying Process

Abstract.

In China, the red jujubes of xinjiang inevitably have happened to have epidermis or slight damage in the process of harvest, transportation and primary processing. The damaged red jujubes have different electrical resistivity and capacitance value. Studies on the dynamic dielectric characteristics of the red jujubes during the drying process can better detect the damaged red jujubes in the process of drying, and improve the quality and grading of the red jujubes in primary processing. The experiment adopts hot air drying method, by setting the drying technology parameters. The results of the test show that, before drying, the testing frequency is equal to or less than 1kHz capacitance Cp value, the inductance Ls value of the damaged red jujubes can be accurately identified; Compared with the normal red jujubes, the various dielectric parameters of the damaged red jujubes have significantly reduced; In the early stage of the drying for 1-5 hours, because of the influence of the expansion of the red jujubes by the hot air drying in the early stage, the dielectric parameters of the normal red jujubes and the damaged red jujubes appear unstable changes, which are difficult to be accurately measured; During the middle-late phase, both the capacitance the inductance change slightly , which makes it difficult to detect the internal defects of the damaged jujube. Hence, it is reasonable to perform the dielectricity-based damage detection during the 1h period right before the drying process.