ASSESSMENT OF A PIN DEFORMATION TEST FOR MEASUREMENT OF MECHANICAL PROPERTIES OF BREAKFAST CEREAL FLAKES

Abstract

ABSTRACTA pin deformation test is assessed for the measurement of the mechanical properties of breakfast cereal flakes where well‐defined procedures like the three point bend test are not easily carried out. These properties are compared with the literature on formed specimens of cereal components, starch polymers and proteins. A classical analysis of a centrally loaded disc on a circular support was used to obtain the Young's modulus, the maximum stress and the maximum strain from the force‐displacement curve. The technique was validated for synthetic polymer discs of known modulus. The Young's modulus for formed discs of starch and gluten as a function of water content agreed reasonably well with independent results using a three point bend test. Formed discs of ground flake showed a similar response to that of gluten. The technique was then applied to individual flakes which were flattened by a hydration‐dehydration procedure and conditioned to different water contents. The stiffness and stress at failure decreased with increasing water content as reported for gluten but their magnitudes were lower, which was attributed to the greater porosity relative to pressed specimens. Some unflattened and low water content flakes were also tested and (although not conforming to the planar geometry of the analysis) showed similarity in stiffness (although not in strength) with their flattened counterparts.