Use of signal to noise ratio and area change rate of spectra to evaluate the Visible/NIR spectral system for fruit internal quality detection

• A spectral measurement system is developed with two types of light source.
• SNR and area change rate of reference spectra are proposed to evaluate the system.
• Results of verification test are matched with SNR and area change rate analysis.

The stability of a spectroscopic measuring system is very important in non-destructive internal quality measurement of agriculture products by Visible and NIR (Vis/NIR) spectroscopy at factory level. However, few works have been published about how to evaluate whether or not the spectroscopic measuring system is reasonable. In this paper, signal to noise ratio (SNR) and area change rate (ACR) of the spectra of reference standard were used to evaluate the Vis/NIR spectral system. Two different systems with different light sources (LS1 and LS2) were considered. The results showed that the SNR recorded at each selected wavelength in the condition of LS1 was higher than that recorded in the condition of LS2, and the ACR between 550 nm and 920 nm in the condition of LS1 was smaller than that of LS2. Meanwhile, in the verification experiment by calibration and cross-validation analysis using fruits, the results obtained in the condition of LS1 were all better than that of LS2, and the best results were correlation coefficient of calibration (rc) = 0.948, root mean square error of calibration (RMSEC) = 0.299°Brix, correlation coefficient of cross-validation (rcv) = 0.924, and root mean square error of cross-validation (RMSECV) = 0.359°Brix. This was well matched to the results of SNR and ACR analysis. This study demonstrates that SNR and ACR of spectra can be used to evaluate the reasonable of the Vis/NIR spectral measuring system.