Apparent amylose content of milled rice by near-infrared reflectance spectrophotometry
1995
Delwiche, S.R. | Bean, M.M. | Miller, R.E. | Webb, B.D. | Williams, P.C.
Amylose content is considered to be the most important factor influencing cooking and processing characteristics of rice. Traditional methods for measurement entail titrimetric, amperometric, or colorimetric measurement of an iodine-binding complex of solubilized starch, but these methods are time-consuming and prone to random error. A method for determining apparent amylose content (AAC), based on the near-infrared (NIR) reflectance spectrum (1,100-2,498 nm) of ground milled rice, was developed on a diverse population of 50 commercial rice varieties or experimental lines grown in the five major rice-producing states of the United States. Three laboratories possessing NIR spectrophotometers participated in a cooperative study. Each laboratory ground, scanned, and developed AAC models by partial least squares analysis, using common sets of samples for calibration (n = 150) and validation (n = 97). Validation set statistics typically indicated r2 = 0.95 and standard error = 1.0% AAC for models consisting of 16-18 factors. Within-laboratory repeatability error of the NIR method was comparable to the reference colorimetric method. Between-laboratory reproducibility error (0.5% AAC) indicated that the NIR models were consistent across laboratories. Such accuracies are considered sufficient for selection in rice breeding programs.
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