Detailed chemical composition of tequesquite, a pre-Hispanic and traditional mineral resource used in Mexico for culinary purposes

Abstract

T equesquite is an alkaline mineral complex used in Mexico with culinary purposes since pre- Hispanic times. It is produced through evaporation and crystallization of remnant for mer Lake Texcoco brackish waters. Despite pre-Hispanic background use of this mineral complex, it was only until the first half of the XX century that analyses were performed to determine its gross chemical composition. However, more detailed information is unavailable in spite of recent technological advances in analytical procedures. In this study samples from different sources were obtained and analyzed to obtain more information about its chemical and elemental composition and to determine possible variations in their composition. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDXRA) and X-ray (XRD) diffraction were employed to determine composition of raw and depurated samples (in which clays and sands were removed through solubilization in deionized water). SiO 2 , NaCl, Na 2 CO 3 , and trona were identified in raw samples, whereas NaCl, trona, K 2 SO 4 , and KCl were detected in samples free of insoluble material. SEM images showed diverse crystal morphology types with different elemental composition, whereas XRD pat terns revealed that tequesquite depicts the same diversity of chemical species despite dif ferent origin. Presence of toxic compounds was discarded, thus confirming its safe use for human consumption. This is the first report of detailed composition of an ancient mineral resource mainly used for culinary purposes that could be of potential use in other applications (e. gr. Spirulina cultivation).