Study On Dielectric Properties Of Honey

Honey is a valuable nutrient loved by people. Honey production and export volume of our country ranked in the world. But there are many adulteration honeys on the market,which not only disturbed the normal market, but also affected the quality of honey. Water and sucrose syrup are the most common adulterated materials. Traditional methods are time-consuming and have complicated procedures. Although high precision, modern detection techniques have disadvantages, such as expensive instruments, complicated procedures, long process time and hign operation ability requirement for user. A large number of studies have shown that the dielectric properties of materials are mainly determined by their composition, measured temperature and frequency. The dielectric properties of honey were studied in order to provide a simple and convenient method for honey detection and provide basic datas for developing instruments.The effect of frequency(10~4500MHz), temperature(20~80℃), water content and sucrose on dielectric properties of yellow-locust, jujube, rape and milk vetch honey was studied. The internal mechanisms of these factors were studied and the relationships between quality and dielectric properties of honey were researched. The conclusions are as follows:(1) The dielectric constants of pure honey and water-added honey solutions decreased with increasing frequency. At the same frequency, the dielectric constants of pure honey and water-added honey solutions increased with increasing water content. The dielectric loss factor of honey and water added honey solutions appeared obvious dielectric relaxation. The relaxation frequency increased with increasing water content, while the maximum loss factors at the relaxation frequencies increased with water content. At the frequency from 650 to 960 MHz, the linear relationships existed between dielectric constant and soluble solid state material or water content,R2>0.995.The penetration depth of honey decreased with frequency.(2) When the frequency was above 40MHz, the dielectric constant of pure honey increased with increasing temperature. The dielectric constants of water-added honey solutions decreased with increasing temperature at the lower frequencies, while increased with temperature at the higher frequencies. Dielectric relaxation obviously existed in the dielectric loss factor of water-added honey solutions. The relaxation frequency increased with increasing temperature, but the maximum of loss factors there showed little change. The penetration depth of pure honey had linear relations with frequency in log-log plot.(3) Electrical conductivity increased with increasing water content or temperature, and changed greatly at higher water content or temperature. Regression model of electrical conductivity as functions of water content and temperature were developed. The linear terms of water content and temperature, quadratic terms of water content, and interaction effect of water content and temperature had significant influence on electrical conductivity. Without the knowledge of honey varieties, the linear coefficient of determination of measured and predicated electrical conductivity was 0.997.(4) The dielectric constant of sucrose adulterated honey decreased with increasing frequency, and dielectric relaxation existed in all adulterated samples. The relaxation frequency did not change with sucrose content. However, the maximums of loss factor decreased with sucrose content. Strong linear correlation was found between loss factor around relaxation frequency and sucrose content,between electrical conductivity and sucrose content.This study aimed to provide basic data for developing water contents and sucrose content meter based on dielectric properties of honey, but also for the use of radio frequency and microwave for honey sterilization.