Study On The Correlation Of Dielectric Properties And Quality Change During Storage Of Lingwu Long-Jujube

Nondestructive detection technology of dielectric properties is an important research direction in fruit detection technology today. LingWu long jujube is a special fresh fruit of Ningxia.Postharvest quick examination of quality and identification,classification sorting,freshness forecasts of the jujube are increasingly urgent.This paper studied long jujube nondestructive testing techniques based on dielectric properties，explored the application and promotion of this technology and provided technical support for the rapid development of long jujube industry.In the experiment,using parallel plate type3532-50LCR Meter,texture Analyzer and chemical detection experiments,dynamic monitoring for LingWu long jujube dielectric parameters and quality (Physical mechanics,internal chemical) during storage were conducted.The experiment was conducted at room temperature.It obtained the correlation of dielectric properties and quality indicators(physical mechanics, biochemistry) of Lingwu long jujube.According to long Jujube microscopic electrical parameters,using BP-ANN neural network,a prediction model of Long Jujube’s quality and freshness was established.The study then provided a theoretical support for the development of real-time, online, rapid non-destructive testing systems.The study also made their preparation for application in industrial inspection.The main results are as follows:(1) The characteristic frequency for nondestructive measurement of LingWu long jujube is3.16kHz.(2) Under the frequency of3.16kHz,the correlation of long jujube dielectric properties and its physical mechanics index of qualities (crispness, hardness, flesh firmness, fruit intensity, burst depth) was studied and the results shown as follows:the dielectric parameters Z,Lp,X of the long jujubes and the crispness,hardness,flesh firmness of the long jujubes showed a significant correlation.Thus,the values of Z,Lp and X can reflect the changes of brittleness,hardness,flesh firmness of the long jujubes.(3) Under the frequency of3.16kHz,the correlation of long jujube dielectric properties and its chemical index of qualities (water,soluble solids,vitamin C,titratable acid) was studied and the results shown as follows:the dielectric parameters Z,Cp,B of the long jujubes can reflect the changes of the moisture,soluble solids. The values of Z and Lp can reflect the change of long jujube’s vitamin C during postharvest storage.The values of Rs and B can reflect the change of LingWu long jujube’s titratable acid_during storage.(4)This paper proposes for the first time an accurate algorithm,which can calculate the sample’s dielectric properties of the microscopic parameters.Relative dielectric constant can be obtained by this algorithm,which can manifest the sample’s microscopic dielectric characteristics preferably.(5) Based on the long jujube’s microscopic electrical parameters (ε’、ε"),using BP neural network,the study established the prediction models of LingWu long jujube’s crispness,flesh firmness, soluble solids and moisture.The correlation coefficients of the model were0.9,0.89,0.83and0.84respectively,The prediction model of the jujube’s freshness levels which was established with BP neural network can predict well the level of jujube freshness.Its accuracy rate can reach81%.