δ13C values and phytanic acid diastereomer ratios: combined evaluation of two markers suggested for authentication of organic milk and dairy products
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Authentication of organic milk by suitable markers is currently attracting more and more interests in food control. In this study, we aimed to compare the efficiency of the markers stable carbon isotope ratio (δ13C value) with the SRR/RRR phytanic acid diastereomer ratio (SRR/RRR) of milk fat for distinguishing different feeding systems. For stable carbon isotope ratio analysis by elemental analysis–isotope ratio mass spectrometry (EA-IRMS), we first developed a simple sample preparation method based on milk fat extracts allowed to evaporate the solvent in tin capsules for liquid samples. The δ13C values and reproducibility measured with this alternative sample pre-treatment method excellently matched those obtained with the current standard method. Applied to milk samples, the results of the EA-IRMS analysis were linked to the SRR/RRR, and both markers allowed to distinguish milk from cows fed with hay (δ13C value > −28.0 ‰, SRR/RRR <1.5) from feed used in conventional milk production which contained maize silage (C4-plants) (p < 0.001). Milk fat of organic retail cheese samples was also highly depleted in 13C (δ13C value −30.0 ‰ ± 1.1), and the SRR/RRR was low (<1.5). However, seven cheese samples showed inconsistent δ13C values and SRR/RRR, most likely due to the feeding of grass silage. Both parameters (δ13C values and SRR/RRR), together with the phytanic acid content of milk fat, also allowed distinguishing between the feeding of high amounts of pasture, hay, and/or grass silage.
KeywordsFood authentication Organic food EA-IRMS δ13C values Milk fat Dairy products Phytanic acid
We are grateful to Raoul von Schmettow and Rainer Funk at the research farm of the University of Hohenheim (Agricultural Experiment Station of the University of Hohenheim, Location Meiereihof, Stuttgart, Germany) for design and performance of the feeding study with the cows and Wolfgang Armbruster for the technical support during the IRMS measurements.
Conflict of interest
The authors declare that they have no conflict of interest.
Compliance with Ethics Requirements
This article does not contain any studies with human or animal subjects.
- 1.Bund Ökologischer Lebensmittelwirtschaft (2011) http://www.boelw.de/uploads/media/pdf/Dokumentation/Zahlen__Daten__Fakten/ZDF2011.pdf, Accessed 9 May 2012
- 11.Boutton TW, Tyrrell HF, Patterson BW, Varga GA, Klein PD (1988) J Anim Sci 66:2636–2645Google Scholar
- 26.Weichbrodt M, Vetter W, Luckas B (2000) J AOAC Int 83:1334–1343Google Scholar
- 30.Fiebig H-J (2011) Deutsche Gesellschaft für Fettwissenschaft: Deutsche Einheitsmethoden zur Untersuchung von Fetten, Fettprodukten. Tensiden und verwandten Stoffen, Wissenschaftliche Verlagsgesellschaft, StuttgartGoogle Scholar