Influence of swelling of vegetable particles on structure and rheology of starch matrices

High volume fractions of dried broccoli particles (up to 20% v/v) were incorporated in a starch dough. The concentration of pre-gelatinized starch was varied between 10% and 30%. The addition of 20% v/v dried broccoli powder causes a significant increase in the shear modulus. For pure starch, the modulus increased with increasing pre-gelatinized starch concentration, whereas the shear modulus of starch containing broccoli particles decreased with increasing pre-gelatinized starch concentration. From viscosity measurements in the dilute regime, the swelling of the broccoli particles was determined. When dispersed in water the dried broccoli particles can swell to up to 7.6 times, and this swelling capacity has a significant effect in the rheological behavior of starch dough systems. When volume fractions up to 20% (v/v) are incorporated, the system acts as a cellular material, instead of a gelled matrix with dispersed particles. This observation was confirmed with confocal scanning laser microscopy.

► Adding high amounts of dried broccoli powder to starch dough affects its rheology.
► Swelling of the broccoli particles is a major factor in the system’s elasticity.
► Particles can swell to about 7.6 times their original volume.
► At 20% (v/v) dried broccoli powder the system behaves like a cellular material.