Sample and sample preparation: pottery sherds 

  • Analysis for microremains can be taken from the charred layer or the clay matrix underneath; however, the charred layer is preferred as the clay matrix contains abundant minerals, which make the recording of the microremains complicated. In ideal cases, both layers should be sampled. 
  • The samples of the charred layer and the clay matrix are usually taken from the inner surface of the pot 
  • To avoid multiple sampling of the same pot, rim sherds are preferred 
  • Foodcrust sample should be thick enough to allow the removal of the uppermost layer to reduce the risk of modern contamination 
  • For comparison, additional samples could be taken from the outer surface of the sherd 
  • Once the uppermost layer is removed, a little amount of foodcrust (minimally 1 mg) is scraped from the sherd with a clean disposable scalpel, wearing sterile nitrile gloves and a lab coat.  
  • The foodcrust is transferred to clean Eppendorf vials, labelled properly (see #) and the weight of the sample added to lab notebook.  
  • Up to 0.2 ml of clean Milli-Q ultrapure water is added to each vial 
  • Vials are sonicated in an ultrasonic bath for 3 minutes.  
  • One drop (approximately 0.05 ml) of the sonicated sample is placed on a microscope slide with a new disposable pipette and a drop of a 1:1 mixture of ultrapure water and glycerole is added to the slide with a new disposable pipette 
  • A coverslip is placed on the slide and secured with nail polish at the corners 
  • The slide is viewed immediately, or if viewing is continued the next day, a drop of ultrapure water is added before viewing.  
  • The sample preparation workflow is described in Chen et al. 2023, Tõrv et al. in prep, and Oras et al. in prep. 

 

Sample and sample preparation: dental calculus 

  • When choosing the tooth for sampling for dental calculus, it should be ensured that the tooth will not be sampled for proteomics or aDNA, as HCl may damage proteins.  
  • The tooth is weighed and photographed. 
  • The sampled tooth is soaked in ultrapure water for a few hours to a few days. 
  • For cleaning the dental calculus from any soil attached to it, an acupuncture needle dipped into 0.1 M HCl is used 
  • Cleaned calculus is removed from the tooth and transported to a clean Eppendorf vial and labelled properly (see #) 
  • The amount of calculus is weighed, and the weight of the sample is added to the lab notebook.  
  • The calculus sample is left in Eppendorf with 0.1 M HCl for about 5 minutes and sonicated in an ultrasonic bath in bursts of 10 seconds to 30 seconds to remove the outermost layer. 
  • The first liquid is pipetted out into a separate Eppendorf and marked as the outermost layer 
  • A few additional drops of HCl are added to the calculus and left until dissolved completely, and then sonicated if necessary 
  • For mounting the slide, one drop of HCl-dental calculus mixture is pipetted out to a clean slide with glycerine-water (1:1) mixture 
  • A coverslip is placed on the slide and secured with nail polish at the corners 
  • The slide is viewed immediately, or if viewing is continued the next day, a drop of ultrapure water is added before viewing. 
  • The sample preparation workflow is described in Unt 2024. 

 

Data Acquisition and Export 

  • Microremains data is generated by scanning through the slide under a microscope with transmitted and cross-polarised light (magnifications 100–500x), so that no spot remains unrecorded. 
  • The observed microremains will be added to an Excel table and structured by kingdoms (plants, animals, fungi) and type of microremains (phytoliths, starch grains, etc.) 
  • The observed microremains will be counted by type and the count added to the table. The table is stored in SharePoint. 
  • Observed microremains will be photographed and the photographs stored in SharePoint as .tiff and .jpg files 

Data Analysis Procedures 

  • The identification of the microremains is done with reference to collection, published literature and databases (PhytCore).  

 

Data reliability/limitations of the method 

  • The process is time-consuming, and only a very small amount of foodcrust will be analysed 
  • There are several limitations regarding the identification of microremains:  
  • The archaeological context can affect the preservation of microremains, e.g. starch grains are destroyed in the presence of water and heat 
  • The food preparation methods can destroy the characteristics of microremains necessary for identification, e.g. grinding damages the phytoliths 
  • The identification of phytoliths can be complicated because of multiplicity (a single taxon produces a range of phytolith shapes and sizes) and redundancy (same shapes are produced by many different taxa) 
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