André Huyghebaert

High pressure-induced gel formation of a whey protein and haemoglobin protein concentrate

High pressure-induced gel formation of whey protein concentrate (WPC), egg white concentrate (EWC), blood plasma concentrate (BPC), and haemoglobin protein concentrate (HPC), was studied at operating pressures up to 4 kbar without additional supply of heat to the pressure vessel. High pressure (4 kbar: 30 min) generated weaker gel networks for WPC and HPC compared to heat set gels (80°C: 30 min) at a given protein concentration of 90 to 180 g/L for WPC, and 80 to 140 g/L for HPC. A minimum operating pressure of 2 kbar for WPC and 3 kbar for HPC, combined with a minimum protein concentration of 160 and 120 g/L respectively, were necessary for network formation to occur. Longer durations generated stronger gel networks, while the effects of repeated compression remained limited. For WPC, only strong high pressure-induced gels were formed in the alkaline pH region. Pressure-sensitive buffer salts (e.g. phosphate) reduced the strength of high pressure-induced WPC gels, presumably caused by lowering the pH under pressure. For BPC and EWC, which easily form heat set gels, no visual gel formation occurred after a pressure treatment of 30 min at 4 kbar.

A comparative rheological study of heat and high pressure induced whey protein gels

Abstract The rheological properties of whey protein concentrate (WPC) gels induced by high pressure (4000 bar/30 min), were compared to those induced by heat (80 °C/30 min) at protein concentrations ranging from 110 up to 183 g/liter. Oscillation measurements at 1 Hz and 0.001 strain showed the highest storage and loss moduli for heat set gels, while creep experiments at a stress level of 40 Pa gave larger sample deformations for high pressure induced gels. Relaxation experiments performed at 17 and 33% deformation were characterized by a higher force decay as a function of time for the high pressure gels, while during compression the compression modulus was always higher in the case of heat set gels. Electron microscopy showed a higher level of cross links in the heat induced gels; high pressure generated a more porous network with a lower amount of intermolecular cross links.