Steam vs. SC-CO2-based extrusion: Comparison of physical properties of milk protein concentrate extrudates

Milk protein concentrate (MPC) is an attractive high protein and low lactose containing ingredient. However, its utilization in extruded products remains a challenge because of its sensitivity to high temperature and shear. This study compares the physicochemical properties of MPC80 extrudates generated with steam vs. supercritical CO2(SC-CO2)-based extrusion. Compared to steam, SC-CO2 extrudates prevented Maillard browning, evident in a significant (P < 0.01) increase in lightness (87.57-89.65), decreased yellowness (16.06-8.31), and increased whiteness (79.49-86.59) indices. SC-CO2 samples had a radial expansion ratio 52% higher than steam and correlated with a reduction in piece and bulk densities (0.21-0.07 g/cm(3) and 0.16 to 0.04 g/cm(3)). The internal morphological structures visualized with SEM showed SC-CO2-expanded extrudates possessing substantially smaller cells and higher cell density. Texture analysis indicated that hardness and Young's modulus of SC-CO2 extrudates were significantly lower than those of the steam-expanded extrudates (35.71-18.35 N and 70.26 to 5.14 kPa).

Automated summary

This study compares the physicochemical properties of MPC80 extrudates generated with steam vs. supercritical CO2-based extrusion. It found that SC-CO2 extrudates had a lighter, whiter appearance, higher expansion ratio and smaller, denser cell structure compared to steam extrudates. Additionally, the hardness and Young's modulus of SC-CO2 extrudates were significantly lower than those of steam-expanded extrudates.