RHEOLOGICAL PROPERTIES OF GUM AND MILK PROTEIN INTERACTIONS

Three different gums (kappa-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-degrees-C for 30 min) or HTST (81-degrees-C for 25 s) pasteurized. Rheological properties were measured the following day using a viscometer. Measurements were made at 4-degrees-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 carrageenan-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.