Steam vs. SC-CO_2-based extrusion: Comparison of physical properties of milk protein concentrate extrudates

摘要

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).