Effect of Microwave Frequency, Water and Inorganic Salts on Dielectric Properties of Wheat Germ

Abstract:

Microwave can stabilize the quality of wheat germ rapidly and uniformly with the advantages of losing nutrition minimally. To investigate the mechanism of microwave on the stability of wheat germ, the dielectric properties (ε′ and ε″) of wheat germ were studied under different frequencies, water contents, fat contents and salts, including sodium, potassium, magnesium, calcium and iron ion. The results showed that, when the frequency was 915MHz, ε′ is slightly higher than that at 2450MHz, while ε″ was less than that at 2450MHz significantly. When water content is 16%, with frequency changes from 915MHz to 2450MHz, ε′ was decreased from 4.91 to 4.32, and ε″ was increased from 0.33 to 0.80. As water content of wheat germ increasing, the dielectric properties of wheat germ were increased significantly. When the water content was increased from 4% to 16%, the ε′ was increased from 2.61 to 4.32, and ε″ increased from 0.02 and 0.8, respectively. Fat content had little effect on the dielectric properties of wheat germ, particularly has no effect on ε″. Among the five salts, adding NaCl can increase ε′ and ε″ of wheat germ. Especially when NaCl concentration was 1%, ε′ was increased slightly while ε″ was increased apparently from 0.8 to 1.3, which can enhance enzyme inactivation effect of microwave.