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An empirical test of shell tempering as an alkaline agent in the nixtamalization process

Upton, Andrew J., Lovis, William A., Urquhart, Gerald R.
Journal of archaeological science 2015 v.62 pp. 39-44
American Indians, archaeology, calcium carbonate, calcium hydroxide, calcium oxide, catalysts, ceramics, corn, diet, fabrics, leaching, nixtamalization, population growth, seeds, shell (molluscs), society, tempering, woodlands, North America, South America
It has been argued that the transition to maize based diets across much of the Eastern Woodlands of North America ca. A.D. 1000 was the primary catalyst for the population increases, technological innovations, and fundamental shifts in social and cultural organization characteristic of Late Woodland, Mississippian, Upper Mississippian, and Iroquoian societies. However, raw or uncooked maize kernels alone are known to be a nutritionally inadequate subsistence staple. Nixtamalization, or the alkaline processing of dried raw maize to produce hominy, yields a more readily digestible and therefore healthier food resource. Such processing is ubiquitous amongst maize-based societies in the Americas. The timing of the transition to maize agriculture was also closely associated with the adoption of shell-tempered ceramics. As a result, an hypothesis has been offered by multiple authors that burned and crushed mollusc shell aplastic may act as an alkaline agent in the nixtamalization process. The research reported here provides a formal empirical test of this hypothesis. Findings indicate that no substantial structural or chemical changes to maize kernels result from the leaching of shell tempering alkaline products from the fabric of a ceramic vessel. Two constraints are noted in this process: the reduction in adherence of wet paste due to the addition of mussel shell derived calcium oxide (lime) or calcium hydroxide (slaked lime) as a tempering agent, and the necessity to avoid the decomposition of calcium carbonate to lime or slaked lime in order for the successful firing of shell-tempered vessels.