Determination of Maximum Viscosity of Milled Rice Flours Using Near-Infrared Transmittance Spectroscopy

The objective of this study was to develop a partial least squares regression (PLS) calibration method of maximum viscosity determination of Japanese milled rice flours using near-infrared transmittance (NIT) spectroscopy. The diversity of spectra and maximum viscosity of wide ranging of rice subfamilies were much more than those of japonica type rices. The variations of spectra and maximum viscosity were found to influence PLS loading weights. C-H and O-H in ROH and H2O absorbances presented by the loading weights were significant in the 8th loading of the PLS model for japonica type rices. The performance of this PLS calibration model (11 components) for maximum viscosity of a rapid visco analyser (RVA) was the standard error of prediction (SEP) of 17.7, square of regression coefficient (R2) of 0.75 and the ratio of the SEP to the standard deviation of the original data (RPD) of 1.9. This method can be applied to the determination of maximum viscosity of japonica type rices

Application of Visible/Near-Infrared Transmittance Spectroscopy for the Improvement of Amylose Determination Accuracy

The performance of partial least squares (PLS) calibration models developed using NIR and visible transmittance were examined in order to improve the accuracy of the calibration model for amylose content. The regression coefficients in the PLS calibration model developed by a full-cross validation using the wavelength region from 570 to 1000 nm (Model B) were smoother and the fluctuations of the coefficients were smaller than the model developed by a full-cross validation using the wavelength region from 850 to 1048 nm (Model A). Significant peaks in the regression coefficients of Model A were characterized by two absorption bands at 928 and 990 nm, and those of Model B were characterized by four absorption bands at 607, 760, 928 and 990 nm. The samples were separated into calibration sets and validation sets, and PLS calibration and validation were also performed. The statistics performance (standard error of performance (SEP), a coefficient of determination (R2)) of the model developed using the wavelength region from 570 to 1000 nm (Model D), was better than those of the model developed using the wavelength region from 850 to 1048 nm (Model C). The SEP of 0.64% on model D examined here was smaller than that of 0.99% on Model C. Therefore, the absorption bands at 607 and 760 nm play an important function in improving the performance of the PLS calibration model