Rheological Properties of Gum and Milk Protein Interactions

Three different gums (κ-carrageenan, guar, and xanthan at concentrations of .05, .10, or .20%) were dispersed in 11% NDM, 11% whey protein concentrate, or double-distilled, deionized water. All solutions were either batch (69°C for 30 min) or HTST (81°C for 25 s) pasteurized. Rheological properties were measured the following day using a viscometer. Measurements were made at 4°C over a shear rate range of 1 to 875 s^–1. Apparent viscosities were calculated and compared at a shear rate of 250 s^–1. A four-factor interaction involving gum type, gum concentration, protein type, and heat treatment was significant. Differences among the means showed that carrageenan-NDM solutions were more viscous than carragman-water solutions when compared at equivalent gum concentrations. The flow behavior index values indicated that, at low gum concentrations, the solutions possessed Newtonian flow behavior, however, at higher concentrations, the flow behavior was pseudoplastic.