A viscometric study of rheological interaction between selected commercial dairy proteins and selected gums in aqueous solution : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University

Abstract

Rheological interaction between solutions of four selected gum (locust bean gum (LB), sodium carboxymethycellutose (CMC), lambda-carrageenan (CR), xanthan gum (XN)) and solutions of four dairy proteins (sodium caseinate (SC), whey protein concentrate (WPC), coprecipitate (TMP), whey protein isolate (WPI)) were studied by steady shear viscometry using a Bohlin VOR Rheometer at 25°C, natural pH and natural ionic strength. The rheological properties of mixed solutions were greatly influenced by presence of gum, gum concentration and gum type. Rheological synergism, with no obvious shear rate dependence, occurred between LB and SC, LB and WPC, LB and TMP, CMC and all dairy proteins, CR and WPC, CR and TMP, and XN and WPC. The degree of synergism, which was determined in a new way, was relatively much greater with TMP. The results are discussed in terms of Ca2+ bridging for TMP synergism and in terms of electrostatic and molecular space occupancy effects for SC, WPC and WPI synergism. No significant interaction occured between LB and WPI or between CR and SC or between CR and WPI or between XN and SC or between XN and TMP or between XN and WPI. Quantitative measures of synergism in mixed solutions prepared from 0.5% gum solution and 6.0% dairy protein solution were in close agreement with similar measures of synergism in mixed solutions prepared from 1.2% gum, 10.0% daily protein and distilled water. Rheogical synergism was found to be unrelated to phase separation in the mixed solutions provided the phases remained intimately mixed. The relevance of this work to the use of the gum-dairy protein mixtures as rheologically-functional food ingredients is discussed.