Gas chromatographic mass spectrometric detection of dihydroxy fatty acids preserved in the 'bound' phase of organic residues of archaeological pottery vessels

Fatty Acids and Starch Identification within Minute Archaeological Fragments: Qualitative Investigation for Assessing Feasibility

Within the realm of archaeology, the analysis of biomolecules assumes significant importance in elucidating historical dietary patterns and their implications for contemporary contexts. To achieve this, knowledge and tools of both chemistry and archaeology are essential to yield objective outcomes and conduct analyses of archaeological materials for the detection of biomolecules. Usually, only minuscule remnants of ceramic fragments are retrieved from excavations, which limits the feasibility of comprehensive laboratory analysis. This study aimed to establish a protocol for analyzing fatty acids and starch from archaeological food utensils with minimal sample quantities. Various experiments were conducted to replicate preparations that might have occurred in archaeological vessels, aiming to establish the optimal protocol. The analyses were performed using clay griddles, subjecting vegetable oil to varying temperatures for fatty acid assessment. For starch analysis, a series of experiments encompassed diverse forms of potato preparations (pulp, chuño, tortilla, carbonization, and freeze-drying) and maize (flour, tortilla, and carbonization). The verification of the experiments was confirmed by conducting identical analyses, as developed in the current study, on authentic archaeological fragments. The principal outcomes of this investigation include the successful extraction of both types of biomolecules using only 0.25 g of the sample, obtained through direct scraping from the vessel. Soxhlet extraction was identified as the most efficient strategy to recover fatty acids. Additionally, a comprehensive protocol for the identification of starch extraction was developed. This study has, for the first time, elucidated two detailed methodologies for the extraction of fatty acids and starch in scenarios in which researchers can obtain limited quantities of archaeological food utensil fragments.

Chemical analysis of pottery reveals the transition from a maritime to a plant-based economy in pre-colonial coastal Brazil

Understanding long-term dynamics of past socio-ecological systems is essential for their future management. The southern Atlantic Forest coast of Brazil with its biodiverse littoral zone and artisanal fishing communities, is a priority for conservation. Traditional maritime knowledge is thought to have a deep-history and indeed, marine exploitation can be traced back to the middle Holocene. As part of one of South America's largest diasporas, Guarani groups reached the southern Brazilian coast at around 1000 years ago. Their impact on the long-standing coastal economy is unknown, due to poor preservation of organic remains. Through the first organic residue study on Guarani pottery, we show that maize rather than aquatic foods was the most dominant product in pottery at this time. By developing a mixing model based on carbon isotope values of saturated and mono-unsaturated fatty acids we propose new criteria for the identification of maize, opening up avenues for future research. Our data confirms the importance of maize to the pre-colonial Guarani, even in a highly productive coastal environment. The Guarani occupation of this region marks a significant departure from previous socio-economic systems, potentially leading to loss of traditional knowledge and alleviating anthropogenic pressure, albeit temporarily, on the marine environment.

A Novel Microwave Hot Pressing Machine for Production of Fixed Oils from Different Biopolymeric Structured Tissues

A microwave hot pressing machine (MHPM) was used to heat the colander to produce fixed oils from each of castor, sunflower, rapeseed, and moringa seed and compared them to those obtained using an ordinary electric hot pressing machine (EHPM). The physical properties, namely the moisture content of seed (MCs), the seed content of fixed oil (S_cfo), the yield of the main fixed oil (Y_mfo), the yield of recovered fixed oil (Y_rfo), extraction loss (EL), six Efficiency of fixed oil extraction (E_foe), specific gravity (SG_fo), refractive index (RI) as well as chemical properties, namely iodine number (IN), saponification value (SV), acid value (AV), and the yield of fatty acid (Y_fa) of the four oils extracted by the MHPM and EHPM were determined. Chemical constituents of the resultant oil were identified using GC/MS after saponification and methylation processes. The Ymfo and SV obtained using the MHPM were higher than those for the EHPM for all four fixed oils studied. On the other hand, each of the SG_fo, RI, IN, AV, and pH of the fixed oils did not alter statistically due to changing the heating tool from electric band heaters into a microwave beam. The qualities of the four fixed oils extracted by the MHPM were very encouraging as a pivot of the industrial fixed oil projects compared to the EHPM. The prominent fatty acid of the castor fixed oil was found to be ricinoleic acid, making up 76.41% and 71.99% contents of oils extracted using the MHPM and EHPM, respectively. In addition, the oleic acid was the prominent fatty acid in each of the fixed oils of sunflower, rapeseed, and moringa species, and its yield by using the MHPM was higher than that for the EHPM. The role of microwave irradiation in facilitating fixed oil extrusion from the biopolymeric structured organelles (lipid bodies) was protruded. Since it was confirmed by the present study that using microwave irradiation is simple, facile, more eco-friendly, cost-effective, retains parent quality of oils, and allows for the warming of bigger machines and spaces, we think it will make an industrial revolution in oil extraction field.

Fishing intensification as response to Late Holocene socio-ecological instability in southeastern South America

The emergence of plant-based economies have dominated evolutionary models of Middle and Late Holocene pre-Columbian societies in South America. Comparatively, the use of aquatic resources and the circumstances for intensifying their exploitation have received little attention. Here we reviewed the stable carbon and nitrogen isotope composition of 390 human individuals from Middle and Late Holocene coastal sambaquis, a long-lasting shell mound culture that flourished for nearly 7000 years along the Atlantic Forest coast of Brazil. Using a newly generated faunal isotopic baseline and Bayesian Isotope Mixing Models we quantified the relative contribution of marine resources to the diet of some of these groups. Through the analysis of more than 400 radiocarbon dates we show that fishing sustained large and resilient populations during most of the Late Holocene. A sharp decline was observed in the frequency of sambaqui sites and radiocarbon dates from ca. 2200 years ago, possibly reflecting the dissolution of several nucleated groups into smaller social units, coinciding with substantial changes in coastal environments. The spread of ceramics from ca. 1200 years ago is marked by innovation and intensification of fishing practices, in a context of increasing social and ecological instability in the Late Holocene.

Comparison of Neutral Compound Extraction from Archaeological Residues in Pottery Using Two Methodologies: A Preliminary Study

This study compares chloroform/methanol extraction and acidic methanol extraction of neutral compounds in absorbed lipid pottery residues from fourteen archaeological sherds. Previous studies have established that fatty acid extraction is more effective with acidic methanol extraction. This study suggests that acidic methanol extraction of neutral compounds, including sterols, alkanols, alkanes, and terpenoids, is more effective than or comparable to chloroform/methanol solvent extraction in most cases. The acidic methanol method extracts sterols, terpenoids, and alkanes more effectively than or comparably to chloroform/methanol extraction.

MASS SPECTROMETRIC FRAGMENTATION OF TRIMETHYLSILYL AND RELATED ALKYLSILYL DERIVATIVES

This review describes the mass spectral fragmentation of trimethylsilyl (TMS) and related alkylsilyl derivatives used for preparing samples for analysis, mainly by combined gas chromatography and mass spectrometry (GC/MS). The review is divided into three sections. The first section is concerned with the TMS derivatives themselves and describes fragmentation of derivatized alcohols, thiols, amines, ketones, carboxylic acids and bifunctional compounds such as hydroxy- and amino-acids, halo acids and hydroxy ethers. More complex compounds such as glycerides, sphingolipids, carbohydrates, organic phosphates, phosphonates, steroids, vitamin D, cannabinoids, and prostaglandins are discussed next. The second section describes intermolecular reactions of siliconium ions such as the TMS cation and the third section discusses other alkylsilyl derivatives. Among these latter compounds are di- and trialkyl-silyl derivatives, various substituted-alkyldimethylsilyl derivatives such as the tert-butyldimethylsilyl ethers, cyclic silyl derivatives, alkoxysilyl derivatives, and 3-pyridylmethyldimethylsilyl esters used for double bond location in fatty acid spectra. © 2019 Wiley Periodicals, Inc. Mass Spec Rev 0000:1-107, 2019.

Digging deeper - A new data mining workflow for improved processing and interpretation of high resolution GC-Q-TOF MS data in archaeological research

Gas chromatography-mass spectrometry profiling is the most established method for the analysis of organic residues, particularly lipids, from archaeological contexts. This technique allows the decryption of hidden chemical information associated with archaeological artefacts, such as ceramic pottery fragments. The molecular and isotopic compositions of such residues can be used to reconstruct past resource use, and hence address major questions relating to patterns of subsistence, diet and ritual practices in the past. A targeted data analysis approach, based on previous findings reported in the literature is common but greatly depends on the investigator’s prior knowledge of specific compound classes and their mass spectrometric behaviour, and poses the risk of missing unknown, potentially diagnostic compounds. Organic residues from post-prehistoric archaeological samples often lead to highly complex chromatograms, which makes manual chromatogram inspection very tedious and time consuming, especially for large datasets. This poses a significant limitation regarding the scale and interpretative scopes of such projects. Therefore, we have developed a non-targeted data mining workflow to extract a higher number of known and unknown compounds from the raw data to reduce investigator’s bias and to vastly accelerate overall analysis time. The workflow covers all steps from raw data handling, feature selection, and compound identification up to statistical interpretation.

Regional diversity in subsistence among early farmers in Southeast Europe revealed by archaeological organic residues

The spread of early farming across Europe from its origins in Southwest Asia was a culturally transformative process which took place over millennia. Within regions, the pace of the transition was probably related to the particular climatic and environmental conditions encountered, as well as the nature of localized hunter-gatherer and farmer interactions. The establishment of farming in the interior of the Balkans represents the first movement of Southwest Asian livestock beyond their natural climatic range, and widespread evidence now exists for early pottery being used extensively for dairying. However, pottery lipid residues from sites in the Iron Gates region of the Danube in the northern Balkans show that here, Neolithic pottery was being used predominantly for processing aquatic resources. This stands out not only within the surrounding region but also contrasts markedly with Neolithic pottery use across wider Europe. These findings provide evidence for the strategic diversity within the wider cultural and economic practices during the Neolithic, with this exceptional environmental and cultural setting offering alternative opportunities despite the dominance of farming in the wider region.

Combined organic biomarker and use-wear analyses of stone artefacts from Liang Bua, Flores, Indonesia

Organic biomarker and lithic use-wear analyses of archaeological implements manufactured and/or used by hominins in the past offers a means of assessing how prehistoric peoples utilised natural resources. Currently, most studies focus on one of these techniques, rather than using both in sequence. This study aims to assess the potential of combining both methods to analyse stone artefacts, using a set of 69 stones excavated from the cave site of Liang Bua (Flores, Indonesia). Prior to chemical analysis, an initial inspection of the artefacts revealed potential use-wear traces but no visible residues. Gas chromatography mass spectrometry (GC-MS) analysis, including the targeting of 86 lipids, terpenes, terpenoids, alkanes and their analogues, found compounds with plant or animal origin on 27 of the 69 stones. The artefacts were subsequently cleaned, and use-wear analysis identified traces of use on 43 artefacts. Use-wear analysis confirmed traces of use on 23 of the 27 artefacts with potential use-residues that were determined by GC-MS. The GC-MS results were broadly consistent with the functional classes identified in the later use-wear analysis. This inclusive approach for stone artefact analysis strengthens the identifications made through multiple lines of enquiry. There remain conflicts and uncertainties in specific cases, suggesting the need for further refinement and analyses of the relationships between use-wear and residues.

Contrasting patterns of prehistoric human diet and subsistence in northernmost Europe

Current archaeological evidence indicates the transition from hunting-fishing-gathering to agriculture in Northern Europe was a gradual process. This transition was especially complex in the prehistoric North Fennoscandian landscape where the high latitude posed a challenge to both domestic animal breeding and cereal cultivation. The conditions varied, the coastal dwellers had access to rich marine resources and enjoyed a milder climate due to the Gulf Stream, while those living in the inland Boreal forest zone faced longer and colder winters and less diversity in animal and plant resources. Thus, the coastal area provided more favourable conditions for early agriculture compared to those found inland. Interestingly, a cultural differentiation between these areas is archaeologically visible from the late 2^nd millennium BC onwards. This is most clearly seen in regionally distinct pottery styles, offering unique opportunities to probe diet and subsistence through the organic residues preserved in ceramic vessels. Herein, we integrate the lipid biomarker, compound-specific stable carbon isotopes (δ¹³C), and zooarchaeological evidence to reveal culturally distinct human diets and subsistence patterns. In northern Norway, some of the coastal people adopted dairying as part of their subsistence strategy, while the inhabitants of the interior, in common with northern Finland, continued their hunter-gatherer-fisher lifestyles.

Analytical Approaches Based on Gas Chromatography Mass Spectrometry (GC/MS) to Study Organic Materials in Artworks and Archaeological Objects

Gas chromatography/mass spectrometry (GC/MS), after appropriate wet chemical sample pre-treatments or pyrolysis, is one of the most commonly adopted analytical techniques in the study of organic materials from cultural heritage objects. Organic materials in archaeological contexts, in classical art objects, or in modern and contemporary works of art may be the same or belong to the same classes, but can also vary considerably, often presenting different ageing pathways and chemical environments. This paper provides an overview of the literature published in the last 10 years on the research based on the use of GC/MS for the analysis of organic materials in artworks and archaeological objects. The latest progresses in advancing analytical approaches, characterising materials and understanding their degradation, and developing methods for monitoring their stability are discussed. Case studies from the literature are presented to examine how the choice of the working conditions and the analytical approaches is driven by the analytical and technical question to be answered, as well as the nature of the object from which the samples are collected.

Different Analytical Procedures for the Study of Organic Residues in Archeological Ceramic Samples with the Use of Gas Chromatography-mass Spectrometry

The analysis of the composition of organic residues present in pottery is an important source of information for historians and archeologists. Chemical characterization of the materials provides information on diets, habits, technologies, and original use of the vessels. This review presents the problem of analytical studies of archeological materials with a special emphasis on organic residues. Current methods used in the determination of different organic compounds in archeological ceramics are presented. Particular attention is paid to the procedures of analysis of archeological ceramic samples used before gas chromatography-mass spectrometry. Advantages and disadvantages of different extraction methods and application of proper quality assurance/quality control procedures are discussed.

Neolithic dairy farming at the extreme of agriculture in northern Europe

The conventional 'Neolithic package' comprised animals and plants originally domesticated in the Near East. As farming spread on a generally northwest trajectory across Europe, early pastoralists would have been faced with the challenge of making farming viable in regions in which the organisms were poorly adapted to providing optimal yields or even surviving. Hence, it has long been debated whether Neolithic economies were ever established at the modern limits of agriculture. Here, we examine food residues in pottery, testing a hypothesis that Neolithic farming was practiced beyond the 60th parallel north. Our findings, based on diagnostic biomarker lipids and δ(13)C values of preserved fatty acids, reveal a transition at ca 2500 BC from the exploitation of aquatic organisms to processing of ruminant products, specifically milk, confirming farming was practiced at high latitudes. Combining this with genetic, environmental and archaeological information, we demonstrate the origins of dairying probably accompanied an incoming, genetically distinct, population successfully establishing this new subsistence 'package'.

Immediate replacement of fishing with dairying by the earliest farmers of the Northeast Atlantic archipelagos

The appearance of farming, from its inception in the Near East around 12 000 years ago, finally reached the northwestern extremes of Europe by the fourth millennium BC or shortly thereafter. Various models have been invoked to explain the Neolithization of northern Europe; however, resolving these different scenarios has proved problematic due to poor faunal preservation and the lack of specificity achievable for commonly applied proxies. Here, we present new multi-proxy evidence, which qualitatively and quantitatively maps subsistence change in the northeast Atlantic archipelagos from the Late Mesolithic into the Neolithic and beyond. A model involving significant retention of hunter–gatherer–fisher influences was tested against one of the dominant adoptions of farming using a novel suite of lipid biomarkers, including dihydroxy fatty acids, ω-(o-alkylphenyl)alkanoic acids and stable carbon isotope signatures of individual fatty acids preserved in cooking vessels. These new findings, together with archaeozoological and human skeletal collagen bulk stable carbon isotope proxies, unequivocally confirm rejection of marine resources by early farmers coinciding with the adoption of intensive dairy farming. This pattern of Neolithization contrasts markedly to that occurring contemporaneously in the Baltic, suggesting that geographically distinct ecological and cultural influences dictated the evolution of subsistence practices at this critical phase of European prehistory.