RHEOLOGICAL CHARACTERISTICS OF MILKFAT AND MILKFAT-BLEND SUCROSE POLYESTERS

Sucrose polyesters (SPE) are non-absorbable, non-caloric potential fat substitutes in foods. Since SPE will be substituted for fats in foods, it is important to determine and compare the rheological properties of SPE with natural fats. The viscous and viscoelastic properties of milkfat were compared to those of milkfat SPE and SPE synthesized from mixtures of 75% milkfat and 25% fatty acids from tallow, myristate, or coconut oil. Liquid viscosities of milkfat and SPE at 50-degrees-C were Newtonian. Viscosities of milkfat, milkfat SPE and milkfat-blend SPE were significantly different (P less-than-or-equal-to 0.05). Milkfat was the least viscous of the samples. The viscoelastic behavior of the fats was characterized at 20-degrees-C by oscillatory tests. SPE storage and loss moduli (G' and G'') were frequency-dependent while the values for milkfat were not. The magnitudes of the storage and loss moduli of the SPE were different. Milkfat was more elastic at 20-degrees-C as revealed by a smaller loss tangent (tan delta = G''/G'). The viscous and viscoelastic properties of milkfat SPE can be adjusted by the addition of small amounts of other fatty acids during synthesis. The rheological properties of milkfat and milkfat-blend SPE were different from those of milkfat.