Food | Yield stress determination of mayonnaise with the rotational rheometer RheolabQC
The yield stress of mayonnaise is important for its processability and spreadability. This report describes the yield stress determination with RheolabQC using a flow curve and the shear stress/deformation method for 25% fat and 80% fat mayonnaise.
Mayonnaise is a semi-solid oil-in-water emulsion, containing 70% to 80% vegetable oil, an acidic aqueous phase, and emulsifiers such as egg yolk. In recent years reduced-fat mayonnaise variants containing 20% to 30% fat have been developed, where oil is partially substituted with water and thickening agents. From a rheological point of view, mayonnaise has a viscoelastic, non-Newtonian character with pronounced shear-thinning behavior and a distinct yield stress.
Yield stress
The yield stress of mayonnaise is an important parameter as it defines the minimum shear stress required to initiate flow. Mayonnaise should flow during processing and spreading, but remain in place during storing and on food. Different methods can be used to determine the yield stress, like flow curve fitting, the shear stress/deformation method or controlled deformation tests. The former two are presented in this report.
Experimental
Two types of mayonnaise were tested (80% fat / 25% fat). Of each sample, 500 mL were filled into a 600 mL beaker, centered by the flexible cup holder. The mayonnaise was then stirred using a spoon to get rid of air pockets. The spindle was immersed and connected to the coupling.
All measurements were carried out with RheolabQC using a vane stirrer (ST22-4V-40) at 22 °C.
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