Hans Barnard: In order to better understand the organic residues found in 4th-6th century CE potsherds (Eastern Desert Ware, from the desert between the Nile and the Red Sea), twenty-five food stuffs were prepared in new vessels (tagen). The crushed walls of these vessels were analyzed using various methods of mass spectrometry and gas chromatography to be compared with data from archaeological material. Sherds of one vessel (X-11) were circulated among participants of this symposium (the round robin experiment), which was initiated as a platform to discuss the problems and possibilities of archaeological  residue analysis.

Jim Cassidy: Global climatic instability 3,700 years ago correlates with the expansion of northeast Asian core-periphery interaction into the frontier area of the Russian Far East. These processes led to the expansion of food production in the form of millet and barley cultivation. In an attempt to gain a more direct understanding of subsistence practices and potential food production represented in deposits dating to this time period a total of 18 Neolithic and 41 Margarita Culture ceramic sherds were subjected to fatty acid residue analysis. This analysis revealed significant data pertaining to subsistence practices, as well as to possible patterns of seasonality.

Marlize Lombard and Lyn Wadley: Fifty-four stone flakes were produced for a series of four blind tests. Some were hafted and used for the processing of plant and animal products. Tools for tests 1,3 and 4 were used to assess the identification skills of the analist who was not provided with any information prior to conducting the analysis. High scores for recognition of residues and tasks performed were obtained (between 85 and 100%). Tools for test 2 were used to study the effects of acidic, organic-rich deposits on plant and animal residues. Sixty-seven additional tools with residues were produced to address problems identified during the first three blind test sessions (tests 1-3). These were used together with those from the blind tests in preparation for performing the fourth blind test in the series, which resulted in the highest score.

Robert Lusteck: While much of this symposium focuses on chemical residues, I would like to highlight the physical residues. Food residues, such as encrustations on pottery, provide an excellent media for the preservation and recovery of micro-botanical remains, especially opal phytoliths. Phytoliths are extremely durable and do not degrade in this context. Once the organic matrix is dissolved, the remaining silica may be analyzed to determine what plants were being prepared in the pot. Therefore, they make a great source of data that complements chemical residue analysis. In this paper, I will discuss my findings from North American samples.

Sean Rafferty: Most residue analysis projects in archaeology focus on recovering evidence of food remains by identifying characteristic protein or lipid compounds. This leaves out many compounds in the natural environment, some of which with pharmacological properties. Most common in this category are alkaloids, which occur naturally in a variety of plants. This paper reviews the potential of alkaloids to provide valuable information on past ways of life, and the current instrumental approaches to their recovery.

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Eleanora Reber: A combination of absorbed residue analysis and typological study is one of the best ways to interpret archaeological pottery use. Applying these techniques to 28 sherds from the Lower Mississippi Valley shows a widely varied diet that continued through time as maize was introduced to the region. Residues provide a new way of looking at archaeological typology and human bevavior.

Henry Schwarcz and Shannon Coyston: We analysed sherds from Preclassic and Classic Mayan sites in El Salvador, Guatemala and Belize. Lipids were found to be adsorbed on sherds which had been used for cooking. Isotopic analysis of charred food residues showed them to be derived from stews with fish as a major constituent. Lipids in these sherds also resembled those of fish. Fatty acid spectra on other sherds were not sufficiently diagnostic to define dietary constituents but indicated a heterogeneous diet including some meat and much plant food. Low concentrations of lipids and lack of specificity in food types make unique identifications difficult.

Questions and discussion mediated by Jelmer Eerkens, Ran Boytner and Hans Barnard.

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Dana Beehr and Stan Ambrose: Carbon and nitrogen isotopes of carbonized residues were analyzed from interior surfaces of 88 ceramic vessel from five contemporary early Mississippian American Bottom sites. Average proportions of maize in upland Richland Complex sites ranged from 7% at a small rural farmstead, to 17% to 42% at three larger sites. Sherds from the Cahokia sub-Mound 51 feasting pit averaged 36% maize, even though macrobotanical remains of maize were very rare. Nitrogen isotope ratios of  eight sherds from Cahokia show meat was cooked in one vessel. Potsherd residue isotopic analysis provides a powerful tool for reconstructing dietary practices in Eastern North America.

Hanneke Hoekman-Sites: Chemical analysis of residues from sherds discovered at Pella of the Decapolis (Jordan) was conducted to examine how the role of the site changed over time. Gas chromatography/mass spectrometry (GC/MS) was used to analyze compounds extracted from 43 Late Byzantine and Medieval sherds. Instead of identifying all possible residues, this study utilized biomarkers to identify specific plant species. Results uphold the view of Pella as a trade center during Byzantine times and suggest trade connections with China and Europe. In the Medieval Period, Pella seemed to have lost its position as a trade center as only local goods were found on Medieval sherds.

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Mary Malainey: Archaeological food residues extracted from areas of fat accumulation in artifacts can be characterized on the basis of relative fatty acid composition. Compositions of ancient residues are compared to experimental residues subjected to periods of oven storage, which simulates the effects of oxidative decomposition over time. Levels of medium and very long chain saturated fatty acids, octadecanoic acid (C18:0) and octadecenoic acid (C18:1) isomers indicate the fat content of the material of origin and probable presence of animal or plant material. This techniques performs well in blind tests of decomposed residues of previously unknown foods and identification criteria remain valid over time.

Micala Rider, Paul Fish, William Longacre, Matthew Young and Mark Malcomson: Due to the highly variable state of the preservation of the organic materials that archaeologists deal with, conclusions drawn on the basis of the primary data from residue analysis are usually ambiguous. Sherds from a Hohokam site in Marana (Arizona) are analyzed by gas chromatography/mass spectrometry (GC/MS) at different stages of their excavation and accession to determine to what extent these processes affect the degradation of the fatty acid residues preserved in the sherd. Preliminary results indicate that fatty acids, particularly the unsaturated acids, do not degrade at the same rates which is of great importance to the analysis and its interpretation.

Robert Parr and Robert Yohe: Visible residues are frequently found in prehistoric ceramic cooking vessels or interior pottery sherds, many seemingly thermally altered. Such residues are apt candidates for residue studies of various types, including analyses focusing on lipids, waxes, carbohydrates, and proteins. Given the low percentage of positive results for identifiable proteins using counter-immunoelectrophoresis (CIEP) on ceramic residues, an experiment was designed to test the viability of immunoproteins following exposure to temperatures at and above 100°C. This paper reports on the results of this study, which suggest that the detection of any protein that has been exposed to high temperatures using CIEP will be severely compromised.

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Questions and discussion mediated by Jelmer Eerkens, Ran Boytner and Hans Barnard.