Nondestructive Detection of Vegetable Moisture Content and Storage Time Using Microwave Free-Space Reflection Method

In this study, a radar traveling-standing wave detection device for the rapid and nondestructive detection of the moisture content and storage time of vegetables was designed based on the microwave free-space reflection method. Spatial traveling-standing waves generated by microwave free-space reflection and superposition were explored and the changes in standing wave ratio and the coordinate of antinode as a function of the moisture content and storage time of vegetables were investigated. The results showed that the proposed models had good prediction accuracy. The goodness of fit (R²) of the moisture content prediction models for lettuce and leaf lettuce were 0.979 and 0.959, and the standard errors of prediction (SEP) were 0.310% and 0.641%, respectively. The R² values of the storage time prediction models for lettuce and leaf lettuce were 0.992 and 0.951, and the SEP values were 0.173 and 0.285 days, respectively. This study provides a new method for nondestructive testing of vegetable quality.