Non-destructive measurement of pear internal quality indices by visible and near-infrared spectrometric techniques

The feasibility of non-destructive measurement of internal quality indices of intact pear fruit using visible and near-infrared (Vis/NIR) spectrometric techniques was studied. In the wavelength region from 350 to 1800 nm, calibration models relating Vis/NIR spectra to soluble solids content (SSC) and firmness were developed based on multi-linear regression (MLR), principal component regression (PCR) and partial least squares regression (PLSR) with respect to the logarithms of the reflectance reciprocal log (1/R), its first derivative D, log (1/R) and its second derivative D-2 log (1/R). The best combination, based on the reliable and robust models obtained, was the PLS models with respect to log (1/R) at an equatorial position of the fruit. Prediction with the PLS model with respect to log (1/R) resulted in correlation coefficients (r(p)) of 0.9121 and 0.8541, and root mean standard error of prediction (RM-SEP) of 0.6619 and 1.2324 for SSC and firmness, respectively. The experimental results indicate that the Vis/NIR spectrometric technique could provide an accurate, reliable and non-destructive method for assessing internal quality indices of pear fruit, especially for SSC.