Visible and Near infrared reflectance spectroscopy for determining soluble solids content of navel orange

Soluble solids content (SSC) is one of the most important quality attributes of navel oranges, either for fresh or for processing market. Since, SSC can be measured only destructively, the results are representative only if carried out on large samples and do not allow classifying marketable fruit one by one according to their specific SSC. As a nondestructive method, Vis/NIR measurement of SSC of fruits is widely studied all over the world. The objective of this research is to determine how Vis/NIR measurements of SSC of navel oranges were affected by spectra pretreatment and various spectroscopic ranges (Vis:400-799 nm; NIR1:800-999 nm; NIR2:1000-1800 mn) using partial least squares (PLS) regression. Spectra correction algorithms, such as multiplication scatter correction (MSC), first derivative (FD) and second derivative (SD) were used and evaluated in this work. The FD correction and PLS produced best noise removing capability and obtained optimal calibration models. This model could predict SSC of navel oranges of prediction set with correlation coefficient (Rpre) of 0.8553 and standard errors of prediction (RMSEP) of 1.6330.