Stable isotope ratio analysis for the authentication of milk and dairy ingredients: A review

As consumers become more conscious of socio-economic, environmental, and welfare implications of their food choices, the authenticity of foods is increasingly important. For dairy products, legal cases challenging “grass-fed” and country of origin claims further highlight the need to scientifically underpin product claims. Stable isotope ratio analysis (SIRA) measures small, naturally occurring differences, arising from known isotopic fractionations, in heavy to light isotope ratios of chemical elements. These ratios provide background information on dairy products including geographic origin, production system, seasonality, and manufacturing processes. This review examines the potential of SIRA to authenticate dairy products, considering commonly used light elements (H, C, N, O, S), and identifies areas for investigation including measurement of less commonly used elements (e.g., Sr, Pb, Ca), analysis of a common component (e.g., casein), and development of comprehensive datasets and isoscapes. The potential for SIRA to authenticate dairy ingredients in complex, processed products is examined.