Differentiating cyclopropane fatty acids to support milk authenticity through GC-MS and NMR spectroscopy

Area of Science:

• Food Science
• Analytical Chemistry
• Animal Nutrition

Background:

• Cyclopropane fatty acids (CPFAs) are potential biomarkers for authenticating premium dairy products.
• Prohibiting silage in feed is crucial for products like Parmigiano Reggiano and Haymilk.
• Understanding CPFA profiles in milk is key to verifying dairy authenticity.

Purpose of the Study:

• To quantify dihydrosterculic acid (DHSA) and lactobacillic acid (LBA) in milk from cows with varying diets.
• To evaluate the efficacy of NMR spectroscopy and GC-MS for CPFA analysis.
• To establish CPFAs as reliable markers for differentiating silage-based feeding regimes.

Main Methods:

• Utilized Nuclear Magnetic Resonance (NMR) spectroscopy for rapid, non-destructive screening of CPFAs.
• Employed a refined Gas Chromatography-Mass Spectrometry (GC-MS) method for precise quantification and separation of DHSA and LBA.
• Analyzed milk samples from cows fed diets with and without silage.

Main Results:

• DHSA levels were approximately threefold higher in milk from cows fed maize silage compared to those on non-silage diets.
• The DHSA/LBA ratio proved to be a robust indicator of the cows' feeding regime.
• LBA showed stable levels across diets and was detected in Haymilk, suggesting alternative metabolic pathways.

Conclusions:

• Combined NMR and GC-MS offer a powerful approach for accurate CPFA quantification in dairy analysis.
• DHSA and its ratio with LBA are effective markers for identifying silage-fed cows.
• Further research into LBA's metabolic origins is warranted for comprehensive dairy authentication.