Salt-modulated structure formation in a dense calcium caseinate system

A 30 wt% calcium caseinate dispersion can be transformed in an anisotropic and fibrous structure by applying well-defined flow and enzymatic gelation. The formation of an anisotropic structure is thought to be due to the micellar structure of the caseinate and the mild adhesion between the micelles caused by the divalent calcium ions. Both micellar structure and interaction can be influenced by the presence of salt in the solution. This paper therefore describes the effect of salt addition on the structure formation. It turned out that the presence of sodium chloride (NaCl) facilitated the structure formation and led to clear development of fibres. Addition of a low concentration of the sequestrant sodium triphosphate (pentabasic; STP) had a similar effect on fibrousness, but reduced the fibre strength. A higher concentration of STP led to homogeneous gel formation and inhibited the formation of a fibrous structure. Rheological measurements were used to explain the results. Dispersions containing NaCl and low concentrations of STP showed non-linear behaviour just as the dispersion to which no salt was added. This rheological behaviour suggested a rearrangement of the internal structure in the protein mixture. The higher STP concentrations resulted in a slightly shear-thinning behaviour of the material, suggesting that the material became less susceptible to structure changes due to shear flow.