Non-Destructive Measurement of Soluble Solids Content and Vitamin C in Gannan Navel Oranges by Vis-NIR Spectroscopy

The potential of visible and near-infrared (Vis-NIR) spectroscopy was investigated for its ability to non-destructively measurement soluble solids content (SSC) and vitamin C (VC) in intact Gannan navel oranges. A total of 238 navel oranges were used for diffuse reflectance Vis-NIR in 350–1800 nm range. In this study, calibration models relating Vis-NIR spectra to SSC and VC were developed based on partial least squares regression (PLSR) with respect to the standard normal variate (SNV) absorbance spectra. Reasonable prediction results (r_p = 0.77, SEP = 0.65 Brix and RSE = 4.96%) were obtained for SSC, while prediction results (r_p = 0.54, SEP = 4.40 mg/100 g and RSE = 8.50%) for VC could not be unacceptable. Multiple linear regression (MLR) models combined with the fingerprint spectra could obtain better prediction performance for SSC and VC in navel oranges, resulting in r_p of 0.80 and 0.55, and SEP of 0.61°Brix and 4.36 mg/100 g for SSC and VC, respectively. The fingerprint spectra analysis is very useful in the field of food chemistry, and further study on other materials is needed to apply this technique.