Non-destructive monitoring of food freezing process by microwave resonance spectroscopy with an open-ended coaxial resonator

摘要

In this study, microwave resonance spectroscopy was applied to monitor the freezing process of food product using an open-ended coaxial resonator. The resonator was designed to detect a signal corresponding to the dielectric property of a product placed in space over a probe. Frozen sucrose solutions with various concentrations and temperatures were employed, and the spectra patterns obtained and their variations upon freezing were investigated. The peak intensities of the spectra were significantly dependent on the concentrations and temperatures of the sucrose solutions, whereas the intensities obtained from pure water (i.e., ice) did not significantly depend on temperature. The dependence of the peak intensities on temperature was found to comprehensively represent the temperature of the core part of the products. The proposed monitoring technique can be employed to detect the status of frozen products in terms of temperature, as demonstrated in the freezing process of a sucrose-agar solution.