Journal oj Cereal Science 10 (1989) 189-197 Effect of Meal Composition and Phytate Content on Zinc Absorption in Humans from an Extruded Bran Product BARBRO KIVISTO*t, AKE CEDERBLADt, LENA DAVIDSSON*, ANN-SOFI SANDBERG§ and BRITTMARIE University of Gothenburg, Departments of * Clinical Nutrition and t Radiation Physics, Annedalsklinikerna S-413 45 GOteborg, Sweden, § Chalmers University of Technology, Department of Food Science, Goteborg, Sweden and the Royal Veterinary and Agricultural University, Research Department of Human Nutrition, Fredriksberg C, Denmark Received 7 April 1989 The effect of extrusion cooking of a high fibre cereal product on zinc absorption was studied using radioisotopic labelling of single meals and measurement of whole-body retention. Thirty-three subjects participated in the study. Three extruded products were tested containing 10% gluten, 20 or 30 % wheat bran and 60 or 70 % starch and compared to the corresponding non-extruded ingredients. One additional product was extruded after reduction of the phytate content. The test products were served with a cooked meal or with milk as the main ingredient of a breakfast. When served with a cooked high protein meal there was no difference in Zn absorption from an extruded product or corresponding raw materials, 36·6 ±2·0 % and 31-8 ±3·1 % respectively. Zn absorption from a breakfast including I SO g of an extruded product was only 6·2 ±0·6 %. However, Zn absorption was greatly improved when the extrusion was performed after reduction of the phytate content. Introduction Extrusion cooking is a widely used food processing technique. It is normally a high temperature-short time (HTST) process using high shearing forces at elevated pressure. It is used for a wide variety of foods such as vegetable proteins, breakfast cereals, weaning foods, crisp bread, snacks and sweets. The nutritional implications of extrusion cooking have been poorly investigated, most concern has been with protein digestibility and starch availabilityl-3 and the implications of the formation of amylose-lipid cornplexes 4 . Very little is known of the effect of extrusion cooking on mineral availability. Lykken et al. 5 found reduced absorption of zinc from a browned corn product (cornflakes) compared to that from an unbrowned product (corn grits) and attributed Abbreviations used: HPLC = high performance liquid chromatography. t To whom correspondence should be addressed. 0733-5210/89/060189+09 $03.00/0 © 1989 Academic Press Limited