Geographical origin of polished rice based on multiple element and stable isotope analyses

Abstract

We determined carbon and nitrogen contents (C and N contents) and stable carbon, nitrogen, and oxygen isotopic compositions (δ13C, δ15N, and δ18O) of polished rice in order to develop a simple method to discriminate its geographical origin. As a first attempt, we examined a single cultivar, Koshihikari rice, from 14 different cultivation areas including Australia (n=1), Japan (n=12), and USA (n=1). For all rice samples, C and N contents and the isotopic compositions are consistent with those of general plant materials, being 37.2–40.0% (C content), 0.8–1.4% (N content), −27.1 to −25.4% (δ13C), +0.4 to +9.0% (δ15N), and +18.8 to +22.9% (δ18O). However, its cultivated area is clearly distinguished by a pentagonal radar plot based on the elemental and isotopic compositions. Thus, the comparison of C and N contents and δ13C, δ15N, and δ18O values would potentially be useful for rapid and routine discrimination of geographical origin of the polished rice.