REPORT ON THE ANALYSES OF THE ORGANIC RESIDUES IN ...

REPORT ON THE ANALYSES OF THE ORGANIC RESIDUES IN ARCHAEOLOGICAL SAMPLES FROM THE PROJECT “EXCAVATING

THE ROMAN PEASANT”.

A. Pecci, ERAUUB, Universitat de Barcelona M.A. Cau Ontiveros, ICREA/ ERAAUB, Universitat de Barcelona

Analyses of the organic residues in ceramics and plasters from the project Excavating the Roman peasant

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ANALYSIS OF THE ORGANIC RESIDUES IN CERAMIC AND PLASTERS FROM THE PROJECT “EXCAVATING THE ROMAN PEASANT” A. Pecci, ERAUUB, Universitat de Barcelona M.A. Cau Ontiveros, ICREA/ ERAAUB, Universitat de Barcelona 1. Introduction

Porous materials absorb the liquid and semi-liquid substances that came in contact with them. In

particular, almost 40 years of research have shown that through the chemical analysis of samples it

is possible to try to understand the original content of ceramic vessels (Condamin et al. 1976,

Evershed 2008).

This kind of analyses has an important application for the study of amphorae, and therefore of the

economy in the Mediterranean area in ancient times. The early stage of chemical analyses of

archaeological materials corresponded essentially to the study of amphorae content (Condamin et

al. 1976, Formenti et al. 1978, Rotshild-Boros 1981, Passi et al. 1981, Heron, Pollard 1988) and in

later years the study of contents has had a new impulse (Garnier 2004, 2007a, 2007b Brun 2004,

Romanus et al. 2009, Pecci 2009). Still, there is still a lot of work to do. Sometimes, in fact, the

analyses offer data that are consistent with those proposed by the literature, while some other times

the content is similar to that one expected, although a little different. Finally, in some cases, they

show new and unexpected data (Pecci et al in press.). This is why it is more and more important to

establish on scientific bases the contents of the different types amphorae, in order to give

consistency to the hypothesis on the goods stored and transported in them, and therefore to

understand ancient economy.

The analyses carried out on some materials recovered during the Project “Excavating the Roman

peasant” have the objective of clarifying if several local-regional amphorae were devoted to contain

wine and to understand the food prepared in two coarse ware cooking vessels.

Residues analysis can also be performed on porous materials different from ceramics, such as

plasters (Barba 1986, 2007). At La Pievina, the plaster coating of a basin was sampled, in order to

try to understand the function of the basin and therefore try to identify food production markers at

the site.

A. Pecci and M.A. Cau, Equip de Recerca Arqueològica i Arqueomètrica de la Universitat de Barcelona

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2. Materials and methods

Materials

Two samples (1-2) were taken from the plastered coatings of a basin. Six samples were

taken from amphorae locally and/or regionally produced, showing a different chronology to test if

changes raised in time, and in particular in Late Antiquity. Two samples were taken from import

amphorae (one K26 and one K25 or 26) and, finally, two samples were taken from Late Roman

cooking ceramic vessels (a testo or pan and a pot) to verify the food cooked in them (Table 1).

Table 1. Samples analysed. sample n. sample id.

laboratory n. part sampled

1 CN2010 -1-US 5005 62 basin us 5005 Plaster 2 CN2010 -2 US 5005 63 basin us 5006 Plaster 3 inv.1010157 64 amphora local-regional Neck 4 inv.1010036 65 amphora local-regional Bottom 5 inv. 1010144 66 amphora local-regional Wall 6 US 5048 67 amphora local-regional Wall 7 US 5014 70 amphora local-regional Wall 8 US 5014 71 amphora local-regional Wall 9 inv.1010130-US 1019 68 amphora K26 Bottom 10 inv.1010090-US 1026 69 amphora K25 or 26 Botom 11 olla inv.1010180-US 1006 72 Cooking pot Bottom 12 testo inv 1010090- 73 Cooking pan Bottom

Methods

Each sample was cleaned mechanically before it was sub - sampled in the laboratory. No

samples of the earth that was in contact with the ceramic vessels and the basin were recovered,

therefore we could not have a blank sample for the analysis.

The samples were studied by the ERAAUB, using the infraestructure of the Archaeometric

Laboratory of the Departament de Prehistòria, Història Antiga i Arqueologia of the Facultat de

Geografia i Història (UB), where the samples were crushed, and the infraestructure of the Serveis

Científico-Tècnics de la Universitat de Barcelona, where the samples were analyzed with

gaschromatografy – mass spectometry (GC-MS).

The ceramic and plaster samples were analysed using the following methodology:

a. The total lipid extract was obtained following the procedure described by Mottram et al. (1999):


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1g of grounded sample was extracted twice with CHCl3/MeOH (2:1 v/v, 3 ml) in sonicated bath for

40 min. at 70°C. 5 µl of a standard solution of octacosane (3 mg/ml) were added to the powder before

extraction. The liquid fraction was recovered after centrifugation and dried using a gentle stream of

nitrogen.

b. Half of the total lipid extract was extracted with KOH in methanol (1 M, 6 ml), leaving overnight.

The day after 6 ml of water were added and acidified. CHCl3 (2x3 ml) was added and mixed with a

vortex. The extract was separated and dried using a gentle stream of nitrogen.

c. For some samples, the solid fraction of each sample was extracted with KOH (1 M, 3 ml) in a

sonicated bath at 70°C for 90 min. After cooling and centrifugation, the liquid fraction was recovered

and acidified. CHCl3 (2x3 ml) was added and mixed with a vortex. The extract was separated and

dried using a gentle stream of nitrogen.

d. For the identification of wine markers, the extraction with KOH was repeated with 500 mg of

sample. This time 3 ml of ethyl acetate were added twice to the liquid fraction and mixed with the

vortex. They were then separated and dried using a gentle stream of nitrogen.

All the extracts were derivatized adding 25µl of N,O-bis(trimethylsilyl)trifluoroacetamide

(BSTFA, Sigma-Aldrich) and heating at 70°C for 1h. 75 µl of hexane were added and 5 µl of a

standard (dotriacontano - 1 mg/mL). For the analysis 1 µl was injected.

The analysis were performed with a chromatographer Thermo Scientific TS GC ultra, with a

30 m x 0.25 mm (i.d.) x 0.25 µm film thickness fused silica capillary column and a mass

spectrometer Thermo Scientific ITQ 900 operated in electronic ionization (70 eV).

The mass range was scanned in the range of m/z 40-650. The oven temperature of the GC was

kept at 50°C for 1 min, and then raised of 5°C/min until the 330°C and kept constant for 10 min.

3. Results

Samples 1-2 sample n. sample id.


1 CN2010 -1-US 5005 62 basin us 5005 Plaster 2 CN2010 -2 US 5005 63 basin us 5006 Plaster

In the total lipid extract of sample 2 the main picks after the standard are oleanitrile and

oleammide (Figures 1 and 2). Also in the hydrolisis of the total lipid extract oleamide is the main

pick. The presence of these compounds could be due to a reaction of oleic acid in a basic

environment, and could therefore be attributed to the presence of a vegetable oil in the sample.


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These compounds were also identified in African amphorae filled with

lime and/or plaster and supposed to have contained oil, that were recovered at Pompei during the

“Garum Workshop project” directed by Bernal and Cottica and studied by the authors of this

contribution.

In the ethyl-acetate extraction, also traces of azelaic acid are present. This compound is

considered to be a by-product of the degradation of oleic acid (Dudd et al 1998).

Figure 1. Chromatogram of the total lipid extract of sample 2 (basin).

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Standard

Standard

Oleanitrile Oleamide

? ?

C16:0 C18:0


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Figure 2. Spectra of the oleanitrile in the sample (top) and in the Nist library (bottom).

Figure 3. Oleamide spectra in the sample (top) and in the Nist library (bottom).

a.(TextFile)10091312#1848RT:32.98AV:1 40

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Samples 3, 4 and 5

sample n. sample id.


3 inv.1010157 64 amphora local-regional Neck 4 inv.1010036 65 amphora local-regional Bottom 5 inv. 1010144 66 amphora local-regional Wall

Samples 3, 4 and 5 come from local-regional amphorae.

While sample 3 is not rich in residues, sample 4 shows very abundant traces of resin/pitch:

dehydroabietic acid is in fact the main pick together with 7 oxodehydroabietic, and abietic acid is

also present.

The abundance of resin in sample 4 could be due to the fact that the amphora was coated with a lot

of pitch, and part of this pitch could have accumulate in the bottom of the amphora

Although in sample 4 the tartaric acid, usually considered to be the marker of wine (Guash Jané et

al 2004, Mc Govern 2004) is absent, there are other compounds that are present in wine, such as

malonic, benzoic, vanillic, succinic, and cinnamic acids, that in sample 9 were identified together

with tartaric acid. These acids, could support the archaeological hypothesis that the amphora

contained wine. In this case, the resin could have also had the function of flavouring the wine.

Sample 5 is also rich in residues. Here, like in sample 4, although no tartaric acid was identified,

other compounds that are usually found in wine are present in the ethylacetate extract (succinic,

benzoic, malonic and vanillic acids). Traces of resin were identified also in this sample, while no

traces of vegetables oils were present in the samples.

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C16:0

C18:0

Dehydroabietic acid

7 oxo dehydroabietic acid

Phtalic acid


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Fugure 4. Chromatogram of the total lipid extract of sample 4. METTERE figura ETO DI 4 e o 5 Figure 5. Ethyl acetate extract of sample... Samples 6, 7 and 8 sample n. sample id.


6 US 5048 67 amphora local-regional Wall 7 US 5014 70 amphora local-regional Wall 8 US 5014 71 amphora local-regional Wall

The analysis of samples 6, 7 and 8, taken from local or regional amphorae show almost no

residues, as the relative proportion to the standards in the total lipid extracts suggests (Figures 6 and

7). In samples 6 and 8, some traces of resin are present, possibly used to coat the amphorae, while

in sample 7, long chain fatty acids such as C20, C21, C22 and C24 were identified. These compounds

could be related with the presence of waxes.

Fugure 6. Chromatogram of the total lipid extract of sample 7 (laboratory 70).

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Fugure 7. Chromatogram of the total lipid extract of sample 8. Sample 9 (laboratory 68)



9 inv.1010130-US 1019 68 amphora K26 Bottom

The analyses of the K 26 amphora (sample 9) allowed to identify tartaric acid both in the

ethylacetate extraction and in the total lipid extract. Tartaric acid is commonly considered to be the

marker of wine. Besides this acid, also other compunds that are typical of wine were identified

(malic, malonic, benzoic, and succinic acids).

Traces of resin are present in all the extractions of the sample.

Azelaic acid and 9,10 - dihydroxyoctadecanoic acids are present in the hydrolyses. These

compounds are usually considered among the markers of oil. Nevertheless, C18:1 is not high and

more data are needed to establish if an oil could have been contained in the amphora. If this was the

case, we could suggest that the amphora was re-used, as it is possible to exclude that oil and wine

were carried together.

The data obtained for this amphora are interesting, as they provide more material for the

discussion on the goods that this kind of amphorae carried. They are in fact supposed to have

carried wine or fish sauces; but the analysis of five K 26 recovered in the port of Classe showed

castor oil residues (Pecci et al in press).

Like in the amphorae coming from Classe, this one had a resin/pitch coating.

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Figure 8. Chromatogram of the hydrolysis in ethyl acetate of sample 9.

Figure 9. Particular of the chromatogram of the hydrolysis in ethyl acetate of sample 9. The markers of wine can be observed here.

Sample 10 (laboratory 69)


Laboratory n. part sampled

10 inv.1010090-US 1026 69 amphora K25 or 26 Bottom

Sample 10, belonging to a K 25 or K 26 amphora, is very rich in pitch. Dehydroabietic acid,

together with 7 - oxodehydroabietic acid are in fact very aboundant in all the extracts. In the

hydrolisis of the total lipid extract also the methyldehydroabietic acid, considered to be the marker

of the distillation of pitch directly from the wood (Colombini et al 2005) is present (Figure..).

The pitch probably due to presence of the coating of the amphora, is so abundant that it might have

Tartaric acid

malonic acid

fumaric acid

malic acid

succinic acid

benzoic acid

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C16:0

C18:0

Phtalic acid

Azelaic acid

9, 10 dihydr

Isocitric acid

C18:1

Dehydroabietic acid


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prevent at least part of the residues of the content from penetrating the

ceramic body. In any case, malonic, benzoic, succinic, glutaric and vanillic acids are present in the

extraction for the wine markers, suggesting a wine content.

Fugure 10. Chromatogram of the hydrolisis on half of the total lipid extract of sample 10.

Fugure11. Spectra of the methyl dehydroabieticacid present in the NIST library (left) and obtained with the analysis of sample 10 (right).

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Dehydroabietic acid 7 oxo dehydroabietic acid

C1810


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Fugure 12. Spectra of the dehydroabieticacid obtained with the analysis of sample 10 and present in the NIST library (bottom).

Sample 11



11 olla inv.1010180-US 1006 72 Cooking pot Bottom Sample 11 was taken from a cooking pot. The abundance of the stearic acid together with the

cholesterol present in some of the extracts, suggests the animal origin of the fats. Although no

isotopic analyses were performed, the presence of branched odd fatty acids such as C15 and C17

suggest that the fat derives mainly from ruminant animals (Mottram et al 1999).

These data are simirar to those obtained with the analysis of Late Roman and Medieval cooking

pots analysed by the authors of this contribution.


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Fugure 13. Chromatogram of the hydrolisis on half of the total lipid extract of sample 11. Sample 12



12 testo inv 1010090- 73 Cooking testo/pan Bottom

Sample 12 was taken from a possible testo or pan. It has abundant residues as it is shown by the

proportion with the standards that can be observed in Figure 13. Like in sample 11, the presence of

cholesterol and the abundance of the stearic acid suggest the animal origin of the fats. Although no

isotopic analyses were performed, the presence of branched odd fatty acids such as C15 and C17

suggest that the fat derives mainly from ruminant animals (Mottram et al 1999).

The quantity of animal origin residues suggests that it is more likely that thevessel was a pan than a

testo. Testi are in fact usually considered to have been used to cook bread or similar foodstuff

(Quiros Castillo 1998, Pruno 2003). Although the analysis of some medieval testi coming from

Tuscan archaeological sites have shown that some of them were possibly used to cook animal origin

products or to serve them on the table (Pecci 2009), the amount of residues present in this ceramic

vessel suggests an intense use for the cooking of animal fats, similar to the one usually performed in

pots or pans.

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Standard C16:0

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C17 br C15 br


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Fugure 13. Chromatogram of the total lipid extract of sample 12.

4. Conclusiones

The results of the analyses allowed to recover in formation on the use of the amphorae and

the basin found at La Pievina.

Some of the amphorae showed residues that could be related with their use, such as the wine

markers present in the K26 and possibly in other amphorae. In other cases no residues were

identified. This could be attributed to the fact that they degraded because of the aging or the post-

depositional processes, nevertheless it is also possible that these amphorae were used for the

storage and transport of water and/or substances that do not leave traces that can be identified with

the analyses performed.

Aknoledgemnts

The samples were analized at the Serveis Científico-Tècnics of the Universitat de Barcelona

in the department of gas chromatography. This report is part of the activities of the project

“Production, trade and consumption of food in Late Antiquity” (PROFOLANT), PIEF-GA-2009-

235863, 7th Framework Programa, People, Marie Curie actions, IEF.

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C181

Standard C17:0 br C15:0 br

cholesterol


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