Rheological and Structural Characteristics of Nanometre-Scale Food Protein Particle Dispersions and Gels

Abstract

Globular whey proteins can be used to create either heat-set gels or cold-set gels. The sizes of aggregates and the creep-compliance behaviour of cold-set gels made from mixing β-lactoglobulin (β-lg) and α-lactalbumin (α-la) depended on the proportion of each protein in the mixture. The particle size (nm) decreased linearly with an increasing proportion of α-la (%) at pH 7.5. The parameters of Burger’s model for creep-compliance data –instantaneous modulus G ₁ , retarded elastic modulus, G ₂ , and viscosity, η – decreased with an increasing proportion of α-la. Fibrils with nanometre-scale diameters from β-lg and α-la were used to create gels with different rheological characteristics. However, more studies have been conducted with β-lg than with α-la. Values of the gelation time, t _c , the critical gel concentration, c ₀ , and the equilibrium value of the storage modulus, ${{G^{\prime}}_{\inf }}$, at long gelation times, derived from experimental rheological data during gelation of β-lg fibrils, are discussed. Fibrils created from β-lg using ethanol-water incubation and heating at pH 2 resulted in gels with different rheological properties, probably because of different fibril microstructures (e.g. persistence and contour lengths) and fibril densities. Partial hydrolysis of α-la with a serine proteinase from Bacillus licheniformis resulted in fibrils that are tubes approximately 20 nm in diameter.