Determination of Apparent Amylose Content in Japanese Milled Rice Using Near-Infrared Transmittance Spectroscopy

The objective of the present study was to develop a method to analyze apparent amylose content (AAC) of Japanese milled rices using near-infrared transmittance spectroscopy (NIT). Samples (n=110, varieties=37), harvested in 1996, were collected at various sites throughout Japan. Whole-grain milled rice was scanned using a near-infrared range (833-1050 nm with 8 nm steps and 27 wavelengths) transmittance filter type spectrometer. The AACs of samples were in the range of 13.1% to 20.7% (SD: 1.53). The wide range AAC (0-35.3%) partial least squares (PLS) model was found to be inadequate for accurate prediction of the narrow AAC range (13.2-20.7%) of the rice samples. The statistical performance of PLS modeling (11 factors) for narrow range AAC analyses gave a standard error of cross-validation (SECv) of 0.78 and square of regression coefficient (R2) of 0.74. The AAC model was applied to 20 unknown samples of products from different crop year (1997), and gave a standard error of prediction (SEP) of 1.25, R2 of 0.49 on the validation set. These results suggested that this model based on NIT spectroscopy could be applied for rapid and nondestructive measurement of narrow range AAC of Japanese milled rices.