Rice quality by spectroscopic analysis: Precision of three spectral regions

Three types of spectroscopy were used to examine rice quality: near infrare d (NIR), Raman, and proton nuclear magnetic resonance (H-1 NMR). Samples fr om 96 rice cultivars were tested. Protein, amylose, transparency, alkali sp reading values, whiteness, and degree of milling were measured by standard techniques and the values were regressed against NIR and Raman spectra data . The NMR spectra were used for a qualitative or semiquantitative assessmen t of the amylose/amylopectin ratio by determining the 1-4 to 1-6 ratio for glucans. Protein can be measured by almost any instrument in any configurat ion because of the strong relationship between the spectral response and th e precision of the reference method. Amylose has an equally strong relation ship to the vibrational spectra, but its determination by any reference met hod is far less precise, resulting in a 10x increase in the standard error of cross-validation (SECv) or standard error of performance (SEP) with R-2 values equal to that of the protein measurement.