Partial Least-Squares Regression Analysis. A PLSR model was used to predict the added starch concentration in onion powder. The samples were categorized on the basis of the adulterant concentration, and a PLSR model was developed using the preprocessed spectra of samples from both FT-NIR and FT-IR spectroscopy. The highest correlation coefficient value, Rp 2 , of 0.98 with a standard error of prediction (SEP) of 1.18% was observed by using the SNV-preprocessed FT-NIR