Tomato firmness estimation using vibration measurements Original Research Article

The use of tomato vibration analysis after impact excitation as a non-destructive physical quality measurement was investigated. For this purpose, an off-line test set-up was constructed that automatically impacts the tomato and captures the response. It is shown that the resonant frequency of the first elliptical mode of the tomato is related to its firmness. The exact location of the resonant frequency was obtained by first smoothing the spectra, and then taking the first derivative. It is shown that smoothing both increases the robustness of the estimates, and also lowers the number of erratic measurements. A comparison is made between measurements taken at the equator of the tomato and the bottom. Due to the non-homogeneity of a tomato, the measurements at the bottom were more reliable.