Mechanisms of lipid preservation in archaeological clay ceramics revealed by mass spectrometry imaging

Significance Lipids, preserved in archaeological ceramics, offer unique insights into past people’s diets and cultural practices. Yet, the fundamental question of how lipids are preserved for millennia is not clear. This study describes the direct visualization of lipids in wall cross-sections of archaeological potsherds using mass spectrometry imaging. Lipids were distributed unevenly in zones of >200-μm size, indicating that macroscopic structures and properties, and not only small pores, facilitate lipid preservation. We also show the formation of calcium fatty acid salts as an additional aspect of lipid preservation. These findings have important implications for the selection of appropriate methods for lipid analysis in potsherds and show that the analysis of lipid distribution patterns could improve and refine interpretations.