Effects of exposure to nixtamalization liquid on bone collagen δ13C and δ15N and archaeological implications

Abstract

The use of stable isotopes in zooarchaeology is common; however, the effects of many cooking and post-depositional processes on the chemical composition of faunal remains are understood poorly. People of the Americas processed maize through nixtamalization, a method of preparing grains by soaking and cooking them in an alkaline solution. Once discarded, nixtamalization wastewater may have contacted other food waste, such as bone. We examine the effects of alkaline exposure on stable isotopes (δ13C and δ15N) in fish bone collagen. Bony structures of four modern shortnose gar (Lepisosteus platostomus), a commonly identified taxon in eastern North American zooarchaeological assemblages, were exposed to four treatments that varied in alkalinity and duration of exposure. No significant differences were observed between treated and untreated specimens in δ13C values. Prolonged exposure to a highly alkaline solution caused a shift in bone collagen δ15N values of approximately −0.44‰. The extreme conditions required to cause this shift suggests that the byproduct of nixtamalization would have negligible effects on archaeological bone collagen δ13C and δ15N values.