Authenticity testing of environment-friendly Korean rice (Oryza sativa L.) using carbon and nitrogen stable isotope ratio analysis

•δ13C and δ15N in rice samples change as a function of cultivation conditions.•δ13C and δ15N allow discrimination of environment-friendly and conventional rice.•δ15N is more useful than δ13C for discrimination of environment-friendly rice.•Two-dimensional δ13C/δ15N plots facilitate authentication of organic rice.•Conventional and environment-friendly rice samples lack pesticide residues.