Fatty Acid- and Amino Acid-Specific Isotope Analysis for Accurate Authentication and Traceability in Organic Milk.

The present study describes compound-specific δC and δN analyses of fatty acids and amino acids for improving the accurate authentication of organic milk (OM) against conventional milk (CM) collected in Korea. Most δC and δC values were lower in OM than in CM ( P < 0.05); however, most δN values displayed weak discriminative power for OM authentication. Higher isotopic fractionation was observed in δC than in δC and δN, with fractionation trends differing with individual amino acids. In particular, δC of -33.5‰ and δC of -28‰ were determined to be promising year-round threshold values for Korean OM authentication. The δC was highly correlated with δC ( r = 0.92) and δC ( r = 0.77), and strong positive correlations were observed between δC and δC ( r = 0.98) and between δN and δN ( r = 0.90). Chemometric modeling for OM authentication produced a high quality model ( R X = 0.547, R Y = 0.865, and Q = 0.689) with reliable chemical markers, notably δC, δC, and δC. Furthermore, the models developed for seasonal separation in OM ( Q = 0.954) and CM ( Q = 0.791) were of good quality. Our findings, based on compound-specific isotope data, improve the reliability of OM authentication in cases where bulk stable isotope ratio analysis alone is insufficient. They also provide valuable insight into the control of fraudulent OM labeling in Korea, with potential application in other countries.