Identification of Aromatic Fatty Acids in Butter Fat

Bovine milk fat contains a large variety of structurally different fatty acids. In this study, we describe the presence of aromatic fatty acids in a butter fat sample. Fatty acids were released from butter fat and converted into the corresponding methyl esters (FAME). Urea complexation was used to separate the main saturated fatty acids. GC/MS screening of the FAME in the filtrate of the urea complexation indicated the presence of aromatic fatty acids. By (1) conversion of two representatives into picolinyl esters which were analyzed by GC/MS, (2) linear log tR over carbon number plots (R 2 = 0.95) and by the use of two reference standards we were able to show that the phenyl unit was located on the terminal carbon of the straight acyl chain of the FAME. In a fraction gathered by countercurrent chromatography we were able to identify 3-phenylpropionic acid (Ph-3:0), 4-phenylbutyric acid (Ph-4:0), 5-phenylpentanoic acid (Ph-5:0), 6-phenylhexanoic acid (Ph-6:0), 7-phenylheptanoic acid (Ph-7:0), 8-phenyloctanoic acid (Ph-8:0), 9-phenylnonanoic acid (Ph-9:0), 10-phenyldecanoic acid (Ph-10:0), 11-phenylundecanoic acid (Ph-11:0), 12-phenyldodecanoic acid (Ph-12:0), 13-phenyltridecanoic acid (Ph-13:0), along with one unsaturated phenyldecenoic acid (Ph-10:1) isomer. Preliminary results indicate that the aromatic fatty acids may have been formed exogenously in the rumen of the cows. The total amount of the aromatic fatty acids was estimated at 0.15 mg/g butter fat, which corresponds with an average daily intake of ~5 mg per day in Germany and ~4.4 mg per day in Europe.