Discrimination between Glutinous and Non-Glutinous Rice by Vibrational Spectroscopy. II: Effects of Spectral Pre-Treatment on the Classification of the Two Types of Rice

Abstract

To measure the amylose content of rice, discrimination between glutinous and non-glutinous rice by vibrational spectroscopy was performed. It was previously demonstrated that classification of raw spectra by the SIMCA method showed the FT-Raman technique provided the best discrimination of classes. In this paper, the effects of spectral pre-treatments such as differentiation and multiplicative scatter correction (MSC) on classification of the rice samples are presented. For FT-NIR DRIFT measurements, differences in classification following different pre-treatments were relatively small but the best classification was obtained with the 2nd derivative pre-treatment, although precision was generally poor. With the PAS spectral sampling method, the classification was better after MSC pre-treatment of raw spectra than either after conversion to the 1st derivative or 2nd derivative. For FT-Raman, the best result was obtained with the MSC pre-treatment. The different effects of pre-treatment on the classification of spectra of the two types of rice probably reflect the information contained in the width of the absorbance bands, because the spectra were collected at 4 cm−1 step with 8 cm−1 resolution. Since the differentiation procedure follows the moving average, very small bands would be eliminated in the process, and would not contribute to the classification analysis. It was noted that effects of fluorescence in the FT-Raman spectra were not removed, even after the MSC pre-treatment.