RHEOLOGICAL PROPERTIES OF WHEAT GLUTEN

Glutens were prepared from four wheat varieties (Kadet, Timmo, Extrem, San Pastore), which perform very differently in cereal products. The dynamic rheological and tensile properties of the glutens were measured by: (i) small angle oscillatory deformation of hydrated glutens in the temperature range 25–100 °C using a Rheometrics mechanical spectrometer to determine dynamic storage (G′) and dynamic loss (G″) moduli; and (ii) large deformation tensile measurement at ambient of heat-set glutens using an Instron Universal testing instrument to measure breaking stress, breaking strain and tensile modulus. The dynamic storage modulus (G′) of hydrated gluten was observed to be wheat variety dependent. When hydrated gluten was heated, G′ decreased steadily until ∼60 °C, when it began to increase, and at approximately 90 °C it increased dramatically. Oxidizing agents increased the dynamic storage modulus (G′), while the use of reducing agents led to a large decrease in G′ and a smaller decrease in loss modulus (G″) resulting in an increase in tan δ (i.e. reduced elasticity). Large deformation tensile properties were dependent on both water content and heat-setting temperature. For heat-set gluten the tensile modulus decreased with increasing water content. The decrease was greater than if water acted solely as a network diluent and suggests that it affects the mobility and interactions of the proteins. Maximum values for the modulus occurred after heat-setting the gluten at approximately 130 °C. Oxidants produced a lower modulus, and particularly a lower breaking stress, while reducing agents caused a dramatic loss of gluten structure prior to heat-setting by reduction of disulphide links. Interestingly, after heat-setting, there appeared to be some reformation of network structure. © 1990, Academic Press Limited. All rights reserved.