Archaeologists find that unglazed ceramic cookware absorbs the chemical residue from current and past meals.
If you happen to be digging an old ceramic pot, do not clean it. Chances are, it contains the culinary secrets of the past.
A research team led by UC Berkeley archaeologists has discovered that non-glazed ceramic cookware can retain the remnants of not only the last cooked dinner, but potentially previous dishes cooked over the life of a pot and open a window to the past.
The results reported in the journal Scientific reports, suggests that gastronomic practices go back millennia ̵
“Our data can help us better reconstruct the meals and specific ingredients that people ingested in the past, which in turn may shed light on social, political, and environmental conditions in ancient societies,” said study lead author Melanie Miller, a researcher at Berkeley’s Archaeological Research Facility. and a postdoctoral fellow at the University of Otago in New Zealand.
In a year-long cooking experiment led by Miller and Berkeley archaeologist Christine Hastorf, seven chefs each prepared 50 meals made from combinations of game, corn and wheat flour in newly purchased La Chamba ceramic pots. This rugged, polished black clay cookware originates from pre-Columbian South America, and the handmade vessels are still popular for preparing and serving traditional foods today.
The group came up with the idea in Hastorf’s archeology of food education seminar in Berkeley. By analyzing the chemical remnants of the meals cooked in each pot, the researchers tried to find out if the deposits found in old cooking containers would also reflect the remnants of the last cooked or previous meals.
In addition to receiving donated deer rides, they purchased large quantities of whole grains and a mill, which Hastorf set up in his garage to grind them. The group then developed a repertoire consisting of six recipes with venison and whole and ground grains.
They chose short ingredients that could be found in many parts of the world. For example, two recipes focused on hominy, which are made from softening corn in an alkaline solution, while two others used wheat flour.
“We chose the food based on how easy it would be to distinguish the chemicals in the food from each other, and how the pots reacted to the food’s isotopic and chemical values,” said Hastorf, a professor of anthropology in Berkeley who studies food archeology, among other things.
How they conducted the survey
Each of the seven chefs prepared an experimental meal weekly in a La Chamba pot using the group’s ingredients. “The mushy meals were boring and we did not eat them,” Miller remarked.
Every eighth meal was charred to replicate the kinds of carbonated residues that archaeologists often encounter in ancient pots and to mimic what would normally happen in the life of a pot. Between each meal, the pots were cleaned with water and a branch from an apple tree. Surprisingly, none of them broke during the study.
At the Berkeley Center for Stable Isotope Biogeochemistry, the team conducted an analysis of the charred debris and the carbonated patins that developed on the pots. Stable isotopes are atoms whose composition does not decay over time, which is useful for archaeological research. An analysis of the fatty lipids absorbed in clay cookware was performed on University of Bristol in England.
Overall, chemical analyzes of the food leftovers showed that different meal scales were represented in different leftovers. For example, the charred bits at the bottom of a pot contained evidence of the most recently cooked meal, while the remnants of previous meals could be found in the patina that built up elsewhere on the inside of the pot and in the lipid residues that were absorbed into the ceramic itself.
These results provide researchers with a new tool for studying diets that are long overdue, and also provide clues to food production, supply, and distribution chains from earlier eras.
“We have thrown the door open for others to take this experiment to the next level and record even longer timelines where food scraps can be identified,” Miller said.
Reference: “Interpretation of Ancient Food Practices: Stable Isotope and Molecular Analyzes of Visible and Absorbed Residues from a Year-Long Cooking Experiment” by Melanie J. Miller, Helen L. Whelton, Jillian A. Swift, Sophia Maline, Simon Hammann, Lucy JE Cramp, Alexandra McCleary, Geoffrey Taylor, Kirsten Vacca, Fanya Becks, Richard P. Evershed and Christine A. Hastorf, 27 August 2020, Scientific reports.
DOI: 10.1038 / s41598-020-70109-8
In addition to Miller and Hastorf, co-authors of the study are Alexandra McCleary and Geoffrey Taylor at UC Berkeley; Helen Whelton, Simon Hammann, Lucy Cramp and Richard Evershed at the University of Bristol; Jillian Swift at the Bernice Pauahi Bishop Museum in Hawaii; Sophia Maline at the University of Southern California; Kirsten Vacca of the University of Hawai’i-West O’ahu and independent scholar Fanya Becks.