Using Iodine Vapour Staining to Visualize Starch Distribution in a Dry, Extruded Food

Abstract

Food ingredients are often made by extruding flours and starches derived from cereal grains with proteins. Extrusion is carried out at high temperature, high shear and low water conditions to make low density, foamed pellets that are used as food ingredients. The structure of the crisp matrix varies greatly with the ingredient proportion and is important in forming the organoleptic properties of the crisps. However, it is very difficult to analyse the structure of the matrix with respect to the distribution of the major components, and the authors have been unable to find references for these materials. Furthermore, the materials must be stained without wetting as water will destroy the integrity of the crisps.