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

Abstract

Herein, we improve the procedure for organic rice authentication using compound-specific δ¹³C and δ¹⁵N 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 δ¹⁵N_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 δ¹³C_amino-acid and δ¹⁵N_amino-acid values. δ¹³C_bulk was correlated with most δ¹³C_fatty-acid (r ≥ 0.596) values, and δ¹⁵N_bulk was strongly correlated with most δ¹⁵N_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 (Q²Y = 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.

Keywords: Chemometric model; Compound-specific isotope analysis; Conventional rice; Organic rice; Pesticide-free rice.