Zinc Bioavailability in a Semolina/Soy Protein Mixture Was Not Affected by Extrusion Processing

Effects of extrusion processing on zinc bioavailability in a product made from 85% semolina and 15% soy protein concentrate were determined using in vitro and in vivo techniques. Soluble and dialyzable zinc contents of the extruded product were 15.3 and 13.0 $\mu$g/g, respectively, compared to 15.6 to 15.0$\mu$g/g in the raw (unprocessed) ingredients. Zinc bioavailability in diets in which all of the zinc (14ppm) was provided either by the extruded product or by its raw ingredients was determined in two groups of male Sprague Dawley rats. No differences were found in concentrations of zinc in plasma, liver and femur between rats fed the two experimental diets. Apparent zinc digestibility was similar for both diets. These results are consistent with the in vitro results showing no effect of extrusion processing on zinc bioavailability.