The old adage you are what you eat (and drink) is perhaps the greatest indicator of culture, status and ethnic identity. In anthropological terms this is referred to as foodways analysis. We will use resonant ionization mass spectrometry to provide direct evidence of foodways from ancient ceramic drinking vessels. Our group is currently preforming a study that builds off of previous research looking for the presence of cacao in Mayan pottery in El Pillar, Belize. Cacao is identified in ancient ceramics through the identification of key molecules that act as biomarkers. Biomarkers are molecules that are found in high concnetrations in the substance of interest, can survive after being burried, and are unique to that substance. For cacao, theobromine, theophylline and caffeine are the biomarkers. We utilize our technique which offers extremely low limits of detection to determine if cacao is present in pottery sherds.
Our studies of foodways are not limited to the Maya but are also extended to ancient Nubia to look for wine in fortress sites. By determining the presence of wine in ancient Egyptian and Nubian vessels, we hope to shed new light on the cultural dynamics between these two rival ethnic groups and how this changed across time and political power shifts. This is done by determining the presence of tartaric acid and malvidin in pottery sherds.
Anthocyanins in wine have been shown to survive over time and their associated phenolic acids can be recovered by alkaline fusion for analysis. The figure below shows the R2PI spectra for five phenolic acids, which we measured in our laboratory. Although in solution, they absorb in the same wavelength region, they each have unique resonance wavelengths under the jet-cooling conditions of our experiment. These specific resonances allow us to selectively ionize each of these components without ionizing any other compounds. Furthermore, comparison of on- and off-resonance mass spectra firmly establishes molecular identification by optical spectroscopy in addition to mass spectrometry.
We have successfully detected these wine markers in a model experiment using modern wine absorbed in a clay vessel. We have also addressed issues of contamination during our preliminary study to exclude any cross-contamination when sampling liquid extracts by employing disposable graphite discs as a desorption substrate. The next phase of this research will focus on analyzing archaeological vessel fragments. Resonant ionization mass spectrometry is highly specific and sensitive and its application would be a first for analyzing archaeological samples.