Rheological characterizations of texturized whey protein concentrate-based powders produced by reactive supercritical fluid extrusion

A powder blend comprising (by weight) 94% whey protein concentrate (WPC80), 6% pre-gelatinized corn starch, 0.6% CaCl2, and 0.6% NaCl was texturized using a supercritical fluid extrusion (SCFX) process. The blend was extruded at 90 °C in a pH range of 2.89 to 8.16 with 1% (db) supercritical carbon dioxide (SC-CO2) and 60% moisture content. The texturized WPC-based (TWPC) samples were dried, grounded into powder, reconstituted in water, and evaluated using a range of rheological studies. Most TWPC samples exhibited shear thinning behavior and their mechanical spectra were typical of weak gel characteristics. The TWPC produced under extremely acidic condition of pH 2.89 with SC-CO2 yielded the highest η∗ (10,049 Pa s) and G′ (9,885 Pa) compared to the unprocessed WPC (η∗ = 0.083 Pa s and G’ = 0.036 Pa). The SCFX process rendered WPC into a product with cold-setting gel characteristics that may be suitable for use as a food texturizer over a wide range of temperatures.