Comparison of mixing and non-linear viscoelastic properties of carob germ glutelins and wheat glutenin

Carob germ glutelins were compared to wheat glutenin from a rheological standpoint to provide a basis for the possible use of carob germ glutelins as a non-gluten protein in gluten-free dough systems. Molecular weight distributions, mixing and non-linear viscoelastic properties of carob germ glutelins and wheat glutenin were compared, while the impact of mixing on non-linear rheological properties of these protein fractions were evaluated over short (4-min) and long (35-min) mixing times. Development time was 13 min for carob germ glutelins, while reaching 500 BU consistency took 34 min for wheat glutenin, suggesting faster hydration for carob germ glutelins due to their relatively lower molecular weight distribution and more hydrophilic nature. Phase angle values revealed similar linear viscoelastic properties for both proteins after 4-min and 35-min mixing. However, Large Amplitude Oscillatory Shear (LAOS) tests indicated type I non-linear behavior for carob germ glutelins and type III non-linear behavior for wheat glutenin after 35-min mixing at which both proteins had similar consistencies, pointing out to weaker stability for carob germ glutelins when exposed to large deformations. Higher degree of strain stiffening and shear thinning behaviors were found for carob germ glutelins in the non-linear region. Increasing mixing time caused a decrease in the strain stiffening behavior of wheat glutenin under large strain-high frequency deformations, while strain stiffening behavior of carob germ glutelins remained similar. Comparing the mixing and LAOS properties of carob germ glutelins to those of wheat glutenin unraveled the processing needs of dough systems where carob germ glutelins could be used as a nongluten protein to produce alternative gluten-free baked products with improved quality.