Comparison of Different Spectrometers for Assessing Soluble Solids Content of Pears On-line by Vis/NIR Spectroscopy

The objective of this research was to compare two different spectrometers for assessing soluble solids content on-line by Vis/NIR spectroscopy. One spectrometer has a CCD detector with 3648 pixels and a wavelength range of 345 nm~1040 nm (defined as spectrometer one). Another spectrometer has a back-thinned CCD detector with 2068 pixels and a wavelength range of 200 nm~1119 nm (defined as spectrometer two). 240 “Cuiguan„ pears which were harvested in different periods and different orchards were used in this study. Absorbance spectra of the pears were acquired using these two spectrometers. The integration time was 100 ms for both spectrometers, and the fruit moving speed was 0.5 m/s. Partial least squares (PLS) combined with several spectral pretreatment methods and multiple linear regression combined with successive projections algorithm (SPA-MLR) were used to develop calibration models. The results indicate that spectrometer two is more suitable for assessing soluble solids content of pears, and that SPA-MLR can obtain acceptable and comparative results to full-spectrum PLS when using the spectra of spectrometer two.