Compositional variation in aged and heated Pistacia resin found in Late Bronze Age Canaanite amphorae and bowls from Amarna, Egypt

Abstract

This study examines resinous deposits from the interior surfaces of sherds of imported Canaanite amphorae and locally produced bowls from the 18th Dynasty site of Tell el-Amarna, Egypt. Archaeological evidence indicates that the Canaanite amphorae were used for resin transport, whilst the bowls are associated with burning resin as incense. A number of characteristic triterpenoids identify all the resinous deposits from both vessel types as Pistacia spp. No other resins were observed and there was no evidence of mixing with oils or fats. The composition of the archaeological resins is more complex than that of modern pistacia resin, due to degradation and generation of new components. Experimental heating alters the relative abundance of the triterpenoid composition of modern pistacia resin. One component, the triterpenoid 28-norolean-17-en-3-one, is produced by such heating; however, an increase in its relative abundance in ancient samples is not matched by the archaeological evidence for heating. It is therefore not possible to use this component reliably to identify heated resin. However, additional unidentified components with a mass spectral base peak at m/z 453 have been associated with seven (out of 10) bowls and are not observed in resins associated with Canaanite amphorae. It is proposed that these components are more reliable molecular indicators of heating.