Determination of Cheese Authenticity by Carbon and Nitrogen Isotope Analysis: Stelvio Cheese as a Case Study

Abstract

This work aims at demonstrating the potential use of isotope ratio mass spectrometry (IRMS) to trace milk samples during Stelvio cheese production chain, one of the most important cheese in the Alpine region. The results showed that isotope fractionation does not occur during the Stelvio cheese manufacturing, regardless to the type of milk used (raw or pasteurized). However, when the isotope values of the main two cheese fractions were independently analyzed (the fat and the resulting defatted cheese fraction), then, the samples prepared with raw milk can be discriminated from those prepared with pasteurized milk. In addition, we also demonstrated that it is possible to detect the presence in cheese of extraneous matter having different isotope values. Proof of the concept was given by replacing raw milk samples (with d13C of −25.1 ± 0.1 ‰) with reconstituted milk obtained from powdered milk samples (having δ13C of −20.4 ± 0.1 ‰). IRMS allowed to detect the presence in cheese of as low as 6.5 % of powdered milk. The results gave evidence that isotopic ratio mass spectrometry is able to trace milk samples along the cheese manufacturing and detect addition of milk or reconstituted powdered milk samples with significant different isotope value.