VISCOELASTIC PROPERTIES OF MIXED DAIRY GELS

Pure and mixed gels prepared from a whey protein isolate (WPI) and ski m milk powder (SMP) by heating to 90-degrees-C at pH 4.3-4.6, with or without fat globules, were studied by mechanical testing. The testing involved compression to 20% deformation and oscillatory rheometry (sto rage and loss moduli, G' and G'', respectively). Compressive stresses of mixed gels varied between 0.7 and 1.9 kPa. Gels containing WPI reac hed higher G' values and had shorter gel-set times than those containi ng SMP. SMP based gels were more elastic than WPI based gels as reveal ed by the lower loss tangent (tan delta = G''/G') values achieved afte r 17 min (0.18-0.23 versus approx. 0.38, respectively). Addition of fa t resulted in higher compressive stresses and shorter gel-set times bu t did not affect the initial gelation rate. Gels with different viscoe lastic and mechanical properties were prepared with varying amounts of WPI, SMP and emulsified fat.