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Title: Stone-boiling maize with limestone: experimental results and implications for nutrition among SE Utah preceramic groups

Author
item EMILY, ELLWOOD - Washington State University
item Scott, Marvin
item LIPE, WILLIAM - Washington State University
item MATSON, RICHARD - University Of British Columbia
item JONES, JOHN - Washington State University

Submitted to: Journal of Archaeological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2012
Publication Date: 1/24/2013
Citation: Emily, E.C., Scott, M.P., Lipe, W.D., Matson, R.G., Jones, J.G. 2013. Stone-boiling maize with limestone: experimental results and implications for nutrition among SE Utah preceramic groups. Journal of Archaeological Science. 40:35-44.

Interpretive Summary: Archaeologists investigating sites inhabited by Native Americans between 200 and 400 A.D. in southeastern Utah believe these people cooked some foods by dropping hot stones into the food because they did not have containers that could withstand direct heating over a fire. Interestingly, limestone seems to be the preferred type of stone used for this purpose. In this manuscript, the authors compare cooking methods in the laboratory and show that when corn is cooked using pre-heated limestone, it is more nutritious than when it is cooked by normal boiling. This is because limestone heated in water produces a chemical that is used in modern-day processing of corn. Thus, the method by which modern tortillas and corn chips are produced may have originated when Native Americans cooked corn by dropping hot stones into a container of corn porridge. This work benefits society by providing historical background to a deep-rooted cultural practice. Further, methods developed for this study may be useful for evaluation of the nutritional quality of corn, benefiting modern corn processors and consumers of corn products.

Technical Abstract: The presence of limestone among midden scatters associated with Grand Gulch phase (A.D. 200 to 400) Basketmaker II period habitation sites (Matson et al. 1988) on Cedar Mesa, southeastern Utah has suggested that these fragments are remnants of stone boiling activities that may have altered nutritional properties of maize (Matson 1991:7). Recent experimental evidence reveals that heating limestone from natural sources on Cedar Mesa to 600° C or higher produces calcination that, in combination with water, creates calcium hydroxide, or slaked lime. Nutritional data from adding the heated natural limestone to a maize and water mixture suggest that this early form of nixtamalization, or lime treatment, produces beneficial results when compared to maize that has simply been boiled. In experimental samples boiled with limestone, the levels of several essential amino acids - tryptophan, lysine, and methionine - are significantly higher than in the control set. As early Basketmaker II groups were largely dependent upon maize (Chisholm and Matson 1994; Coltrain et al. 2006; Matson and Chisholm 1991; Reed 2002:9), and the grain is nutritionally insufficient on its own (Mertz et al. 1970; Wacher 2003), higher levels of these amino acids may have been made available through nixtamalization.