Olive oil or lard?: Distinguishing plant oils from animal fats in the archeological record of the eastern Mediterranean using gas chromatography/combustion/isotope ratio mass spectrometry
Article first published online: 5 NOV 2010
Copyright © 2010 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry
Volume 24, Issue 23, pages 3478–3484, 15 December 2010
How to Cite
Steele, V. J., Stern, B. and Stott, A. W. (2010), Olive oil or lard?: Distinguishing plant oils from animal fats in the archeological record of the eastern Mediterranean using gas chromatography/combustion/isotope ratio mass spectrometry. Rapid Commun. Mass Spectrom., 24: 3478–3484. doi: 10.1002/rcm.4790
- Issue published online: 5 NOV 2010
- Article first published online: 5 NOV 2010
- Manuscript Revised: 15 SEP 2010
- Manuscript Accepted: 15 SEP 2010
- Manuscript Received: 14 JUL 2010
Distinguishing animal fats from plant oils in archaeological residues is not straightforward. Characteristic plant sterols, such as β-sitosterol, are often missing in archaeological samples and specific biomarkers do not exist for most plant fats. Identification is usually based on a range of characteristics such as fatty acid ratios, all of which indicate that a plant oil may be present, none of which uniquely distinguish plant oils from other fats. Degradation and dissolution during burial alter fatty acid ratios and remove short-chain fatty acids, resulting in degraded plant oils with similar fatty acid profiles to other degraded fats.
Compound-specific stable isotope analysis of δ13C18:0 and δ13C16:0, carried out by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), has provided a means of distinguishing fish oils, dairy fats, ruminant and non-ruminant adipose fats, but plant oils are rarely included in these analyses. For modern plant oils where C18:1 is abundant, δ13C18:1 and δ13C16:0 are usually measured. These results cannot be compared with archaeological data or data from other modern reference fats where δ13C18:0 and δ13C16:0 are measured, as C18:0 and C18:1 are formed by different processes resulting in different isotopic values.
Eight samples of six modern plant oils were saponified, releasing sufficient C18:0 to measure the isotopic values, which were plotted against δ13C16:0. The isotopic values for these oils, with one exception, formed a tight cluster between ruminant and non-ruminant animal fats. This result complicates the interpretation of mixed fatty residues in geographical areas where both animal fats and plant oils were in use. Copyright © 2010 John Wiley & Sons, Ltd.