Properties of partially denatured whey protein products: Viscoelastic properties

摘要

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 ingredients that will offer food manufacturers greater control over the texture of formulated fluid foods. (C) 2018 Elsevier Ltd. All rights reserved.