Properties of partially denatured whey protein products: Viscoelastic properties
View/ Open
Date
2018-02-07Author
Euston, Stephen R.
Lonchamp, Julien
Campbell, Lydia
Arrighi, V.
Zhang, Z.
Metadata
Show full item recordCitation
Euston, S., Lonchamp, J., Campbell, L., Arrighi, V. & Zhang, Z. (2018) Properties of partially denatured whey protein products: Viscoelastic properties. Food Hydrocolloids, 80, pp. 298-308.
Abstract
Partially denatured whey protein products (PDWPC's) can be classified based on the viscoelastic properties of their
solutions. Strain sweeps show that PDWPC-A and -B and microparticulated WPC (MPWPC) with compact, spherical
aggregated particles exhibit a strong strain overshoot. PDWPC-C and -D, on the other hand, which have open,
elongated porous particles show a weak strain overshoot. The concentration dependence of the elastic modulus G' in
the linear viscoelastic region has a biphasic power law dependence with concentration for all protein products studied,
except for WPC where G' is independent of protein concentration. Frequency sweeps suggest that MPWC solutions
form a strong physical gel at all concentrations above 14% (w/w). PDWPC-A and -B form weak gels over the same
concentration range. PDWPC-C and -D also form weak gels at 14% protein (w/w) but strong physical gels at higher
concentrations. The frequency dependence of G' and G'' for all aggregated proteins show a power law dependence
indicating fractal type structures. For all solutions above a critical concentration, the fractal dimensions span the range
1.6-2.3, indicating a range of gel network structures from open and diffuse to compact and dense. Adherence to the
empirical Cox-Merz rule was observed in PDWPC-A, -C and -D at concentrations of 14 and 16% (w/w) protein,
suggesting liquid-like behaviour. At higher protein concentrations the deviations from the Cox-Merz rule suggest more
pronounced elasticity in the structure. For PDWPC-B, the behaviour is complex, with deviation from the Cox-Merz rule
at low frequencies/shear rates, but correspondence at higher frequencies/shear rates at all concentrations. This
indicates a frequency-dependent change from liquid-like behaviour over long timescale deformations, to a solid-like
behaviour at short timescale deformations. MPWPC solutions of all concentrations do not follow the Cox-Merz rule,
suggesting solid-like behaviour. The PDWPCs exhibit a complex rheological behaviour which suggests they could be
versatile thickening, texturizing and fat replacement