[Near-infrared spectrum detection result influenced by navel oranges placement position]

The present paper studies the near-infrared spectroscopy of soluble solids content in navel orange that was influenced by different placement positions of the navel orange. According to the different angles between incident light and the straight line composed by navel orange stems and pit, the authors chose three different placement positions,vertical (90 degrees), parallel (0 degrees) and random(not including 0 degrees and 90 degrees). The authors acquired the semi-transmission spectrum of the navel orange placed in different positions in the wavelength range of 465-1 150 nm by the miniature fiber spectrometer USB4000, there were 336 navel orange samples in the experiment, 228 samples weree used as calibration set, and the rest 108 samples were used as prediction set. The authors used partial least-square regression combined with different pre-processing methods to establish the prediction model of SSC in navel orange with different placement positions. The result shows that when the angle is vertical the prediction models of SSC in navel orange are good, and the best correlation coefficient of the model is r = 0.93, RMSEC = 0.37%, r, = 0.88, and RMSEP = 0.49%.