Functional properties of plant proteins Part 7. Rheological properties of succinylated protein isolates from faba beans (Vicia faba L.)

The flow behaviour of unmodified and succinylated protein isolates from faba beans (FBPI) was studied in dependence on the degree of succinylation, temperature and protein concentration. The dispersions of exhaustively succinylated I-BPI which represent unfolded proteins show structural viscosity and high yield values at room temperature and tend to jellify without heating. There exists a critical degree of succinylation (between 50 and 80%) at which the unfolding of the proteins begins. In the unmodified and moderately succinylated proteins this unfolding is characterized by a minimum of viscosity at a transition temperature and a sharp viscosity increase by further heating in the cyclic heating-cooling diagram. The “transition” temperature of unmodified FBPI is identical with the “critical” temperature of aggregation in dilute solution. Flow curves of 10% dispersions of FBPI show a decrease of shear stress t with increasing succinylation up to a moderate degree of modification. The 49% succinylated sample shows the lowest value of t and nearly Newtonian fluid behaviour.