Visible (Vis)/near infrared (NIR) spectroscopy is an excellent technique for non-destructive fruit quality assessment. This research was focused on evaluating the use of Vis/NIR spectroscopy for measuring soluble solids content (SSC) of intact 'Cuiguan' pears (Pomaceae pyrifolia Nakai cv. Cuiguan) on-line. Also, the effect of fruit moving speed on SSC measurements was investigated. Diffuse transmission spectra were collected using a fiber spectrometer equipped with a 3648-element linear silicon CCD array detector in the wavelength range of 345-1040 nm, and all sample spectra were collected three times at different fruit moving speeds of 0.3 m s-1, 0.5 m s-1 and 0.7 m s-1. Spectral pre-processing such as derivative, standard normal variate transformation (SNV) and multiplicative scatter correction (MSC) was used before calibration. Partial least squares (PLS) and least squares support vector machines (LS-SVM) were used to develop calibration models for SSC. The results show that fruit moving speed has few effects on spectra and model performance at a fruit moving speed of 0.3-0.7 m s-1. At 0.5 m s-1, the best model for SSC was PLS regression coupled with original spectra, its coefficient of determination (R2) and root mean square error of prediction (RMSEP) being 0.916% and 0.530%, respectively.
- Fruit moving speed
- Least squares support vector machines
- Partial least squares
- Soluble solids content
- Visible/near infrared spectroscopy