Geographical differentiation between South Korean and Chinese onions using stable isotope ratios and mineral content analysis.

Abstract

Geographical origin authentication of onions has become significant owing to origin labelling fraud in South Korea. Various analytical techniques based on stable isotope ratios, organic and inorganic constituents, or their combinations, can distinguish agricultural products geographically. However, studies on the geographical classification of South Korean and Chinese onions using stable isotopes and minerals remain scarce. This study aimed to discriminate geographically between South Korean and Chinese onions using stable isotope ratios (δ¹³C, δ¹⁵N, and δ³⁴S) and mineral contents (K, Ca, Mg, Na, P, Fe, Zn, Mn, Cu, and Sr) combined with multivariate statistical analysis. Fifty-eight onion samples cultivated in South Korea and China were collected in 2023. The two stable isotope ratios (δ¹⁵N and δ³⁴S) and six minerals (K, Ca, Na, Fe, Zn, and Sr) significantly differed between these onions. These variables were applied in orthogonal partial least squares discriminant analysis to classify the onion samples regionally. The predictive ability and goodness-of-fit parameters (R²X and R²Y) were 0.671, 0.383, and 0.677, respectively. K, Sr, δ³⁴S, and Na served as potential markers contributing to the classification. Therefore, stable isotopes and mineral elements may serve as effective indicators for the geographical discrimination of South Korean and Chinese onion samples using multivariate analyses.