Concentrations of phytanic acid and pristanic acid are higher in organic than in conventional dairy products from the German market

Abstract

Abstract Differentiation of organic and conventional dairy products is an important, yet difficult task in food authentication. In this study it was tested whether phytanic acid and pristanic acid can be used as markers for this purpose. Phytanic and pristanic acid cannot be de novo synthesised by mammals, and the predominant source for uptake is chlorophyll in food. Highest concentrations (but still in the sub-gram per 100 g lipids range) are found in ruminants because rumen bacteria are able to release phytol from chlorophyll and transforming it into phytanic acid. Degradation of phytanic acid leads to pristanic acid, and both fatty acids usually co-exist in biota. Owing to the unique source of grass-based feedstuffs in organic farming it was tested whether organic cheeses (n = 13) and other organic dairy products (n = 5) are higher in phytanic and pristanic acid concentrations than conventional products (n = 12). For this purpose, a sensitive gas chromatography–mass spectrometry method in the selected ion monitoring mode was developed. Organic cheeses contained on average 50% more phytanic acid and 30% more pristanic acid, while concentrations of 14-methylhexadecanoic acid (a17:0), i.e. another minor fatty acid in ruminants, were only slightly increased by 8%. A target value of at least 200 mg/100 g phytanic acid was suggested for the verification of grass-fed, organic dairy products. Some conventional products also reached the target value, and this indicated that the cows that gave the milk were also fed with grass-silage. On the other hand, only one organic cheese fell below this target value. It is recommended to control manufacturers whose organic dairy products show concentrations of below the target value of 200 mg phytanic acid per 100 gram lipids in order to confirm the application of organic principles.