Deuterium depletion in the fatty acids from beef

Abstract

We examined stable hydrogen (δD, ‰ relative to V-SMOW) and carbon isotopic compositions (δ 13 C, ‰ relative to V-PDB) of fatty acids extracted from beef, and compared them with those from feeds (mixtures of plant materials) for the cattle. The δD value of stearic acid in beef is similar to that in the feeds, whereas the palmitic and oleic acids in beef are both significantly depleted in D (by ca. 60‰) as compared with the corresponding acids in the feeds. On the other hand, these fatty acids in beef are enriched in 13 C (by up to 5.7‰) relative to the corresponding acids in the feeds. Thus, the isotopic compositions of fatty acids in beef are not identical to those in the feeds. These results suggest that fatty acids in beef are an admixture of fatty acids derived from de novo biosynthesis in the cattle and from the feeds, and may imply that a considerable D-depletion process (e.g., hydrogenation of feed-derived fatty acids and/or dehydrogenation–hydrogenation cycling) occur in the fatty acids of the cattle.