Organic Residue Analysis (ORA)

Using Organic Residue Analysis (ORA) we can extract and characterise lipid residues that become absorbed within the porous fabric of ceramic vessels or the charred matrix of visible crusts, both of which offer added protection to the absorbed lipid residues, therefore increasing their survival potential over archaeological timescales. By studying the lipid profile, vessel content can be identified and we gain significant knowledge on how natural products were used in the past. We do this using a targeted biomarker and isotopic approach, and Gas Chromatography and Mass Spectrometry techniques to separate and characterise our lipid biomarkers.

ORA provides a wide breadth of data, including which organic products were used in the past and how they were processed. ORA is key in palaeodietary studies as it will identify food products processed in cooking pots or trapped within the fabric of serving (e.g. cups and bowls) or storage (e.g. amphorae) vessels. Our approach allows us to identify local and non-local products, hence addressing wider archaeological questions. The ability of ORA to identify pot content will provide direct evidence for vessel function. Tars, pitches and resins used in technological processes, such as the production of adhesives and sealants (e.g. pine, birch bark, and beehive products) are regularly identified using ORA, as are fats and oils used in embalming processes, ancient medicines and cosmetics. More recently, Sequential Thermal Desorption/Pyrolysis-Gas Chromatography-Mass Spectrometry has been used to identify lipids trapped within dental calculus. This methodology has already revealed a myriad of information pertaining to diet, the surrounding environment and the use of the mouth as a third hand.