Detection of Variety Contamination in Milled Japanese Rice Using a Single Kernel near Infrared Technique in Transmittance Mode

Abstract

An authentication system for identifying the purity of a milled rice bulk using near infrared (NIR) protein determination was established. NIR spectra from 1100 nm to 1800 nm of single kernels acquired with fibre optics in transmittance mode were used. First, the effect of the degree of milling (DOM) on the NIR protein determination was examined. Then, to obtain a robust and accurate protein measuring system, a calibration equation was developed with variety and DOM compensation. Finally, by examining the normal distribution of the protein content measured by the single kernel NIR spectroscopy, a blended bulk could be separated from a pure bulk as it did not exhibit a normal protein distribution while a pure one did. However, the system would have less capability if the average protein content of the contrasting variety was close to that of the main variety. In the naturally acquired protein histogram, the system proposed had the capability to detect the blending when the Koshihikari bulk included 5% or more Akitakomachi kernels.