Influence of ph and sodium chloride on the high pressure-induced gel formation of a whey protein concentrate

Whey protein concentrate (WPC) gels induced by high pressure (4000 bar/ 30 min) at a protein concentration of 132 g/liter in the presence and absence of NaCl, 0.5 mol/liter, and at pH-values ranging from 3 to 9, were characterized by rheology, electron microscopy, and gel dissolution tests performed in the presence of bond breaking agents (salts, urea, SDS, DTT). A weak coagulum was formed around the IEP (pH 4-5). Below the IEP, gel formation did only occur in the presence of NaCl. At pH 3, gels showed a high force decay during relaxation, and were stabilized by electrostatic and hydrogen bonds. Gel networks produced above the IEP showed a high gel strength and G′-value, and a low force decay during relaxation. NaCl acts negatively on their rheological properties, while disulfide bonds contribute significantly to the stabilization of these gels. © 1997 Elsevier Science Ltd