268 Calcium in corn tortillas.

D. Sahai, M. Buendia, M. Rowe, I. Surjawan, J. P. Mua, and D. S. Jackson. Dept. of Food Science & Technology, 123b Food Industry Building, University of Nebraska– Lincoln, Lincoln, NE 68583-0919.

Corn tortillas are an important source of calcium and a daily staple for many people in Mexico and Central America. Corn nixtamalization and tortilla preparation methods are not standardized; process variables influence tortilla nutritional characteristics. Cook temperature, cook time, steep time, lime concentration and extent of washing, critically influence nixtamal calcium uptake and tortilla calcium levels. Response Surface Methodology (RSM) was used to study the impact of four processing variables (cook temperature, cook time, steep time and lime concentration) on changes in tortilla calcium. A central composite design with 27 experimental trials was used as an experimental design. Tortilla calcium content was measured by atomic absorption spectrophotometry. Tortilla calcium exhibited significant RSM linear regression models with all measured processing variables (p < 0.05). Besides lime concentration, steep time was observed to be an important factor influencing tortilla calcium. Under processing conditions studied, tortilla calcium was 320–480% greater than initial corn calcium. Overnight steeping (12 hours) is essential for the production of high calcium tortillas, when initial added lime is in the range of 0.88 to 1.6% (corn weight basis).