Estimation of soluble solids content of intact citrus fruit by Vis/NIR spectroscopy

Visible/Near-infrared (Vis/NIR) spectroscopy has become a very popular technique for the non-invasive assessment of intact fruit. The feasibility of using Vis/NIR spectroscopic technology for rapid quantifying soluble solids content (SSC) of citrus fruit was investigated by means of spectral transmittance mode. A total of 110 citrus fruit samples were used to develop the calibration and prediction models. The relationship between actual SSC and Vis/NIRS spectra of citrus fruit samples was analyzed via pricipal component regression (PCR) and partial least squares (PLS) regression method using TQ 6.2 spectral analysis software. Models based on the different spectral pre-processing methods were compared in the present research. Performance of different models was assessed in terms of root mean square errors of prediction (RMSEP) and correlation coefficients (r(2)) of prediction set of samples. The best predictive models feature a RMSEP of 0.538% and correlation coefficient (r(2)) of 0.801 for SSC. The results show that the Vis/NIR transmittance technique is a feasible, accurate and fast method for non-invasive estimation of citrus fruit SSC.