The experimental identification of nixtamalized maize through starch spherulites

Abstract Nixtamalization is a cooking technique that has played a significant role for thousands of years in the foodways of indigenous communities throughout the Americas. By cooking maize in an alkaline solution, often made from slaked lime, the process of nixtamalization increases the nutritional value of maize and helps to prevent severe malnutrition in populations dependent on maize as a staple food source. Due to the preservation bias against macrobotanical remains in tropical soils, microbotanical analyses of pottery residues are increasingly used to identify ancient plant use and preparation. However, to date no method has been developed to directly identify nixtamalization in the archaeological record via residue analysis. Through experimental replication of the nixtamalization process we have identified a unique product of the lime-based alkaline cooking process: residues that we conclude are starch spherulites. Here, we detail the range of diagnostic morphologies characteristic of starch spherulites and propose that the presence of starch spherulites found on cooking vessels and grinding stones, or within archaeological sediments, can act as a proxy for the use of the nixtamalization process. Through applications of polarized light microscopy, scanning electron microscopy, and SEM-EDS, this research lays the groundwork for the direct identification of nixtamalization in archaeological contexts, offering for the first time a direct mechanism with which to assess the inception and expansion of nixtamalization throughout the Americas.