Compound-specific δ13C and δ15N analyses of fatty acids and amino acids for discrimination of organic, pesticide-free, and conventional rice (Oryza sativa L.)

Herein, we improve the procedure for organic rice authentication using compound-specific delta C-13 and delta N-15 analyses of fatty acids and amino acids, addressing the increasing demand for accurate methods to confirm organic authenticity. Organic rice (OR) and pesticide-free rice (PFR) featured higher values of delta N-15(bulk) than conventional rice (CR), whereas the corresponding differences between OR and PFR were insignificant. Additionally, OR, PFR, and CR could be discriminated based on some delta C-13(amino-acid) and delta N-15(amino-acid) values. delta C-13(bulk) was correlated with most delta C-13(fatty-acid) (r >= 0.596) values, and delta N-15(bulk) was strongly correlated with most delta N-15(amino-acid) (r >= 0.834) values. The first component in the orthogonal projection to latent structure-discriminant analysis model allowed for a clear separation between OR and PFR, and good predictability (Q(2)Y = 0.506). Thus, the present study improves the reliability of organic authentication when bulk stable isotope ratio analysis alone is insufficient for the accurate discrimination of OR, PFR, and CR.