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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
Author(s) -
Steele Valerie J.,
Stern Ben,
Stott Andy W.
Publication year - 2010
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.4790
Subject(s) - chemistry , isotope ratio mass spectrometry , saponification , fatty acid , animal fat , chromatography , environmental chemistry , mass spectrometry , gas chromatography , ruminant , isotopes of carbon , food science , organic chemistry , biology , ecology , total organic carbon , crop
Abstract 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 δ 13 C 18:0 and δ 13 C 16:0 , 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 C 18:1 is abundant, δ 13 C 18:1 and δ 13 C 16:0 are usually measured. These results cannot be compared with archaeological data or data from other modern reference fats where δ 13 C 18:0 and δ 13 C 16:0 are measured, as C 18:0 and C 18:1 are formed by different processes resulting in different isotopic values. Eight samples of six modern plant oils were saponified, releasing sufficient C 18:0 to measure the isotopic values, which were plotted against δ 13 C 16:0 . 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.