Studies on bioavailability of some bulk and trace elements in mexican tortilla using an in vitro model

An in vitro gut model was used to investigate the bioavailability of calcium, magnesium, cadmium, chromium, iron, manganese, and lead in the Mexican (maize) tortilla. The samples (4 g) were digested in quartz tubes using concentrated nitric acid (12 mL) at 65‡C (2 h) and then at 120‡C (4 h). Total element concentration was determined by atomic absorption spectrometry. Enzymatic hydrolysis was carried out in two steps: first, with pepsin in a hydrochloric acid medium (pH 1.8) and then after neutralization with sodium bicarbonate (pH 6.0), with the mixture of pancreatine, amylase, and bile salts extract. Elements under study were determined in the supernatant by atomic absorption spectrometry. The bioavailable fraction of each element in tortilla was evaluated as the percentage of total element content found in the solution after enzymolysis. The obtained results showed relatively low bioavailability of the selected elements (from 2% to 32%), which possibly may be ascribed to the presence of dietary fiber in tortilla.