Traceability of origin enhances the branding and safety of agricultural products. This study developed a subregional milk origin tracing method by selecting thirty large-scale farms: twenty-seven in Ningxia and three in Beijing. The farms were classified into six groups based on subregions: A (Yinchuan), B (Shizuishan), C (Qingtongxia), D (Yanchi), E (Zhongwei), and F (Beijing). Milk, soil, and drinking water samples were analyzed using isotope mass spectrometry and ICP-MS. Multivariable statistics revealed significant differences among groups. A strong positive correlation existed among milk, soil, and water. Positive correlations were found between δ2H and δ18O in milk and water, as well as δ15N in milk and soil. Four key variables (K, Na, Ca/Sr, and δ2H in milk water) were identified for differentiating milk origin, achieving a 93.8 % correct classification rate. This study showed that milk from contiguous subregions has different isotopic and element fingerprints that can be utilized for traceability.
Keywords: Discriminant analysis; Isotope fingerprint; Ningxia milk; Origin traceability; Trace elements.
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