DETECTING RICE QUALITY AS INFLUENCED BY HULLING USING VISIBLE AND NEAR-INFRARED SPECTROSCOPY

Visible and near-infrared (VIS/NIR) spectroscopy calibration models for rice taste evaluation were developed Sakha, 101 short-grain rice variety. The best performance calibration model was obtained from original spectra of whole grain milled rice using multiple linear regression (MLR) analysis. The correlation coefficient (R^2) and the standard error of prediction (SEP) of the validation set was 0.83 and 0.31, respectively for estimated taste value. Near-infrared transmission (NIRT) spectroscopy was used in an attempt to predict moisture content, protein content and amylose content from un-dried whole grain rough and milled rice spectra. Using partial least squares calibration models obtained from un-dried whole grain rough and milled rice spectra, the coefficient of determination (R^2) and the standard error of prediction (SEP) of the validation set were R^2 = 0.96 and SEP = 0.46 for rough rice moisture content, R^2 = 0.82 and SEP = 0.31 for brown rice protein content, R^2 = 0.87 and SEP = 0.29 for milled rice protein content, and R^2 = 0.04 and SEP = 0.25 for milled rice amylose content. The results of the validation indicated that NIRT could be used to determine moisture content and protein content but not the amylose content. Thus, NIRT technology may be used to classify un-dried rough rice into qualitative groups such as high protein content rice and low protein content rice upon arrival at a rice-drying facility after harvesting. The results also indicated that VIS/NIR technology could be used for classifying rice samples into qualitative groups, such as poor taste, better taste and the best taste. However, taste of rice and its acceptability need to be considered to adopt lower degree of milling. A predicted equation was obtained for rice taste value depending on some physicochemical composition such as protein, amylose, moisture content, fat acid and taste value from the experiment data. According to the principle of the taste analyzer, rice taste value may be directly calculated with the content of the compositions measured at laboratory.