Rheological behaviour of wheat endosperm - Proposal for classification based on the rheological characteristics of endosperm test samples

A simple, rapid method for the preparation of parallelepiped-shaped samples from a grain is used in the proposal of a study of the rheological behavio ur of wheat endosperm. Compression rupture, creep and relaxation tests are used. A series of compression rears on mealy and vitreous endosperm of different wheat varieties (soft, hard and durum) shows that the rheological propertie s are influenced by both the generic origin and grain vitreousness. The mai n mechanical characteristics Young's modulus, elastic and rupture stresses, rupture energy and rupture strain-were determined at moisture contents of 12 to 17%. The influence of the moisture content on rheological behaviour i s demonstrated. The vitreous endosperm of some wheat varieties displays considerable ductil ity before rupture. The nature of this plasticity was analysed by creep and relaxation tests on hard and soft wheats. Comparison of the different endosperm rheology values clarifies the notions of vitreousness and hardness. Wheal classification based on endosperm mech anical characteristics is proposed. It seems that Young's modulus character ises hardness whereas rupture energy is related to the vitreousness of the different varieties studied. Entering the results in a Youngs modulus ruptu re energy system leads to a classification of wheats according to two essen tial factors: hardness of varietal origin and vitreousness of cultural orig in. (C) 2001 Academic Press.