Effect of total solids content and temperature on the rheological behaviour of reconstituted whole milk concentrates

This work investigated the combined effect of solids content, heating and storage temperatures on the rheological behaviour of reconstituted whole milk concentrates. The powder was reconstituted at 35 degrees C in a custom built recombination rig to various total solids content (TS) from 10-48% TS. The concentrates were then heated to 45-85 degrees C and stored at the heating temperature. The rheological behaviour shifter from Newtonian behaviour (below 30% TS) to power law (below 40% TS), with the yield stress observed from 40% TS upwards and time-dependent behaviour was noticed above 44% TS. Higher heating temperatures tend to promote non-Newtonian behaviour at lower solids content. The viscosity-solid content curve showed an exponential relationship, while the viscosity-temperature curve exhibited a minimum at 65-75 degrees C above 46% TS. During age thickening, the yield stress and the consistency coefficient increased, while the flow behaviour index decreased with storage time. This indicated that the milk concentrates deviated away from Newtonian behaviour during age thickening.