Tool detects maize cooking in archaeological record

A new method can spot a specific way of cooking maize to boost its nutrition—nixtamalization—in the archaeological record.

Two questions motivated the research: How did people interact with plants in the past? And how did they use food as an expression of their identities?

“I am particularly interested in understanding the ways that this identity and the role of food production was negotiated as societies become increasingly hierarchical, and politically and economically complex,” says paleoethnobotanist Emily Johnson, a doctoral student in anthropology at the University of California, Santa Barbara.

“The increased reliance on a few staple crops, such as maize, that often occur with this shift can be detrimental unless adaptations are made to the diet.”

What’s nixtamalization?

Those adaptations include nixtamalization, a production process for maize known to play a significant role—for thousands of years—in the foodways of indigenous communities throughout North America, yet never before explicitly affirmed in the archaeological record.

Johnson, based in the Integrative Subsistence Laboratory of her advisor, professor Amber VanDerwarker, has developed the first direct method to identify nixtamalization in the past. Her research appears in the Journal of Archaeological Science.

“Prior to this paper, it was not possible to directly identify the process of nixtamalization in the archaeological record—it could only be hypothesized to occur at sites with proxy evidence such as grinding stones and ceramic griddles,” Johnson says. “However, these items can also be used for a variety of other processing activities distinct from nixtamalization. Now, archaeologists can better understand the inception and spread of this significant cooking practice throughout time and space.”

How to make maize nutritious

The research is significant, says VanDerwarker, because “it allows a path forward for archaeologists to identify when maize-growing groups throughout North and Central America adopted the technology of nixtamalization. We know that native groups adopted this technology before European contact, but until now it has been impossible to identify directly when this transition occurred archaeologically.”

The process of cooking maize in an alkaline solution, VanDerwarker explains, dramatically improves the nutritional content of maize, which is deficient in various amino acids, vitamins, and minerals. Doing so helps to prevent severe malnutrition in populations dependent on maize as a staple food source.

“Emily’s work has been able to demonstrate that maize starch grain morphology changes during this process, and the starches from before versus after nixtamalization are highly diagnostic,” she says.

Traces of starch in cookware

For the research, Johnson replicated the nixtamalization of maize in an effort to understand whether the damage from cooking impacted the starch granules—the primary component of maize—in significant and identifiable ways. By identifying these changes, nixtamalization could then be directly identified in the archaeological record by recovering the damaged starch granules from objects such as cooking and serving vessels and ground stone used to process the maize.

“While some studies have looked at how processes such as grinding, roasting, and boiling have affected starch granules, no one has previously looked at how nixtamalization affects starch granules,” Johnson says. “Unique to this region, nixtamalization has become a way to not only boost the nutritional profile of maize, but a cultural element in its own right. The first step in the process of turning maize into masa for tortillas, tamales, and more, it is clear that this cooking technique is still relevant to the health and cultures of people today.”

The next step in continuing this line of research, Johnson says, is to identify these modified starch granules in the archaeological record. She and VanDerwarker already have identified sites in the Southern Gulf lowlands in Mexico with long occupation histories and existing evidence of maize-dominated diets that “would be ideal for investigating when, where, and how this process began.”

Coauthor John Marston of Boston University oversaw Johnson’s undergraduate work on the project.

Source: UC Santa Barbara