Ad. Errington et Ea. Foegeding, FACTORS DETERMINING FRACTURE-STRESS AND STRAIN OF FINE-STRANDED WHEY-PROTEIN GELS, Journal of agricultural and food chemistry, 46(8), 1998, pp. 2963-2967
Whey proteins form translucent heat-induced gels at low and high pH th
at differ in fracture properties. Gels formed at pH 7.0 and 6.5. were
strong (fracture stress of 59-92 kPa) and rubbery (fracture strain of
1.7-1.2). Gels formed at pH 3.0 and 2.5 were weak (fracture stress of
17-19 kPa) and brittle (fracture strain of 0.33-0.39). Altering disulf
ide bond formation changed gel texture. Addition of a disulfide reduci
ng agent (dithiothreitol) at concentrations greater than or equal to 2
5 mM, at pH 7.0, caused the gel to weaken (>46% reduction in fracture
stress) and become brittle (fracture strain of 0.30-0.32). Increasing
the number of disulfide bonds in gels formed at pH values 13.5 increas
ed fracture strain to 2.0 while causing a minor increase in fracture s
tress. Formation of disulfide bonds appears to be essential to the def
ormability of heat-induced whey protein gels.