Nondestructive evaluation of jujube quality by visible and near-infrared spectroscopy

This study compared prediction ability of interactance, transmission measurements of visible and near-infrared (Vis/NIR) spectroscopy in detecting the soluble solids content (SSC) of jujubes. Calibration models relating Vis/NIR spectra to SSC were developed based on partial least squares regression (PLSR) with respect to the logarithms of the reciprocal absorbance (log (1/R)), its first and second derivatives (D(1)log (1/R), D(2)log (1/R)). The PLSR models for prediction samples resulted correlation coefficients (r(p)) of 0.74-0.91 and root mean square error of prediction (RMSEP) of 2.018-3.200 degrees Brix for interactance; r(p) of 0.63-0.73 and RMSEP of 3.517-3.863 degrees Brix for transmission, respectively. The results indicate that interactance displays an obvious advantage over transmission measurement. The reflectance measurement was used to access the discrimination potential in sorting external insect-infested jujubes from intact class. Stepwise discriminant analysis (SDA) was performed to identify the effective wavelengths that best discriminated the insect-infested jujubes from intact jujubes and to derive a discriminant function in classifying the jujubes showing external infestation and those that were free of infestation. The results showed that log (1/R) had better correct classification rate than D(1)log (1/R), and D(2)log (1/R) for classifying intact, insect-infested and stem-end classes. (C) 2010 Elsevier Ltd. All rights reserved.