Food Residue

Food residue includes numerous different types of remains.  Some examples are:

1) the residue that appears to be charred or burned onto ceramics,

2) charred food residue that occurs as lumps in hearths or on floors or storage pits of burned structures B these are usually noted in macrofloral samples

3) invisible food residue B although these exist, they are not the topic of this page

Any burned or charred residues can be examined for phytoliths, which do not suffer from exposure to temperatures used to cook foods, nor to methods used to breakdown the carbonized food residue.  Sometimes starches survive both cooking and later lab extraction.  Sometimes the larger pieces of charred residue either have structure that is identifiable on a macro level or contain macrofloral remains.  Pollen is not expected to survive the charring process if it involved direct contact with open flame, although pollen can be present in some of the residue adhering to ceramics.

Food residue adhering to ceramics might be the result of accumulation of froth that accumulates when cooking starchy foods.  When froth is present, it usually adhers to the rim of vessels and to the outer surface of the vessel.  Especially when indentations or incised lines are present as part of the design, food residue can fill these spaces and be retained for sampling.  We have successfully retrieved Zea mays phytoliths from this type of residue adhering to ceramic cooking vessels.

Method for Sampling Food Residue Adhering to Ceramics

We would be quite happy to remove the residue for you.  If you want to do it yourself, this is an outline of or process.  We would like to talk to you before you start this process yourself.  First, thoroughly clean the ceramic, including the residue, of loose dirt.  Next, dry brush the area to remove loose dirt.  If possible, sonicate the ceramic with the residue to coax out any dirt that has infiltrated the porous residue.  You would see this as a cloud coming from the residue during sonicating.  Use distilled water with a few drops of detergent as the liquid in which to sonicate the ceramic.  Next, dry the ceramic with the residue.  When the residue is thoroughly dry, remove it with a dental pick onto a clean piece of paper.  Then transfer the bits to a clean, tiny zip-lock bag (1 2@ X 2" or 2" x 3") or to a 1.5 ml. centrifuge vial.  You may then send this for analysis.

One More Note:

When examining charred or burned residue to identify what food(s) is/are represented, one should take into account which foods produce phytoliths prior to requesting analysis.  If phytolith-producing foods are not available in your geographic area or time period, we should talk about appropriate analysis.

Updated 6/20/03