Applicability of organic milk indicators to the authentication of processed products

The validity of established threshold values for the analytical authentication (stable isotopes and fatty acids) of organic drinking milk in Germany was determined for more strongly processed organic dairy products (n = 56). Milk fat extracted from both soft and semi-hard cheeses, butter, cream, sour cream, buttermilk, yoghurt and low-fat milk always possessed an α-linolenic acid (C18:3ω3) content above the minimum level of 0.50% and a stable isotope ratio of carbon (δ13C) below the maximum level of −26.5‰ required for organic milk. Noncompliant results were obtained for whey as well as both Italian ice creams and cheeses. Analyses of German cream cheese and curd lipids revealed that 7 out of 39 samples did not comply with the two thresholds. An additional analysis of δ13C in the defatted dry matter showed that these reconstituted products apparently contained a combination of organic skim milk and conventional or imported organic cream. The inherent correlation between δ13C in the fat and defatted dry matter indicates their different origins, which may provide evidence of fraud. This study showed that the previous C18:3ω3 and δ13C thresholds are generally applicable to processed dairy products from Germany. An analysis of δ15N in defatted dry matter confirmed the recently proposed threshold of ⩽5.5‰ for organic dairy products.