The team looked at differentiating cheeses from cows fed silage and those that were not.
Cyclopropane fatty acids (CPFA), as lactobacillic acid and dihydrosterculic acid, have been detected in milk and in dairy products from cows fed with corn silage, when they are not, CPFA is not found.
A quantitative gas chromatography–mass spectrometry (GC–MS) method to detect CPFA was developed, and quality parameters (limit of detection, limit of quantitation, and intra-laboratory precision) were assessed.
Limit of detection and quantitation of CPFA were, respectively, 60 and 200 mg/kg of cheese fat.
GC–MS analysis was carried out on an Agilent Technologies 6890N gas chromatograph coupled to an Agilent Technologies 5973 mass spectrometer. A low-polarity capillary column (SLB-5 ms, Supelco) was used.
Mérieux NutriSciences said earlier this year it had created a testing method to identify authentic Parmigiano Reggiano cheese which involved high resolution accurate mass (HRAM) and statistical software to develop a model to distinguish between closely related cheeses.
Higher prices of protected denomination of origin (PDO) products encourage more frequent counterfeiting.
Parmigiano Reggiano cheeses with the PDO label must be produced in a restricted area of Italy and made out of milk from cows that are not fed silage, a fermented cereal product often used in animal feed. It costs more than double what generic similar cheeses cost.
The method was applied to 304 samples of PDO cheeses of certified origin, including 200 samples of Parmigiano Reggiano (Italy), 68 of Grana Padano (Italy), 16 of Fontina (Italy) and 10 each of Comté (France) and Gruyère (Switzerland).
Results showed that CPFA were absent in all of the cheeses whose Production Specification Rules forbid the use of silages (Parmigiano Reggiano, Fontina, Comté, and Gruyère).
CPFA were present in variable concentrations (300–830 mg/kg of fat) in all samples of Grana Padano cheese (silages admitted).
Traditional analysis by the Parmigiano Reggiano Cheese Consortium (CFPR) to differentiate Parmigiano Reggiano from major commercial hard-type cheese brands are determination of soluble nitrogen and free amino acids (evaluation of ripening time), presence of the added lysozyme and amount of copper.
Researchers said spectroscopic techniques had been tested to determine the degree of ripening and the geographical origins of Parmigiano Reggiano (for example, nuclear magnetic resonance, stable isotope analysis combined with multielemental analysis and middle and near-infrared spectroscopy coupled with statistical techniques).
A mix of grated Parmigiano Reggiano and Grana Padano also showed the method could detect the counterfeiting of Parmigiano Reggiano with other cheeses up to 10–20% Grana Padano content.
Presence of CPFA could be used as one of the markers of Parmigiano Reggiano authenticity, said the researchers.
“The quantitative method proposed is relatively simple, assures a quick sample preparation, and relies on available instrumentation, thus making it suitable for the screening of a large number of samples with a good cost-per-analysis ratio.”
Source: Journal of Agricultural and Food Chemistry, 2016, 64 (20), pp 4158–4164
“Development of a Quantitative GC–MS Method for the Detection of Cyclopropane Fatty Acids in Cheese as New Molecular Markers for Parmigiano Reggiano Authentication”
Authors: Augusta Caligiani, Marco Nocetti, Veronica Lolli, Angela Marseglia and Gerardo Palla