Characterization of Mayonnaise with DWS Microrheology

 

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From the MSD data, the software of the DWS RheoLab calculates the frequency dependent elastic modulus G'(ω) and the loss modulus G''(ω). As normalization parameter, the average size of the oil droplets is required and is directly entered in the corresponding field in the RheoLab software. To predict the rheological properties we assume a mean value of 10 µm based on the optical microscope studies by Hou-PinSu et al. [4]. Figure 3 shows the resulting data for the model mayonnaise (only three xanthan concentrations are shown for better readability) and the commercial low-fat mayonnaise. All data sets show a solid behavior (i.e. G'>G'') over the accessed frequency range, except at very high frequencies (>104 rad/s). With increasing xanthan content, the curves shift towards higher moduli. This observation, combined with the shape of G' and G'', is in line with the assumption that the xanthan in the continuous phase of the emulsion forms a weak gel where the gel strength increases with the xanthan concentration [5]. The mesh size of the xanthan gel is on the order of 40 nm for a xanthan concentration of 0.5 wt% [5], and is thus much smaller than the oil droplets.

 

At low xanthan concentration, the gel has low stiffness (see Figure 3) and the oil droplets are relatively free to diffuse which leads to a MSD with pronounced positive slope towards large lag times (see Figure 2). In contrast, at high xanthan concentrations, the gel has sufficient stiffness to trap the oil droplets, which reduces the MSD values at larger times significantly.

 
 

Storage moduli (full lines) and loss moduli (dashed lines) of the model mayonnaise with different xanthan content compared to the commercial product.

 

Figure 3. Storage moduli (full lines) and loss moduli (dashed lines) of the model mayonnaise with different xanthan content compared to the commercial product.

 
 

Conclusion

 

We applied DWS microrheology to a series of model low fat mayonnaises with different contents of thickener (xanthan) and to a commercial low fat mayonnaise. We could show that this novel characterization technique allows quantitative measurements of the effect of the thickener in the formulation and enables us to carry out a comparison with a commercial product.

This study demonstrates the advantages of DWS microrheology to support the formulation process of emulsions stabilized by hydrocolloids during the development and for quality control. All measurements were conducted with the DWS RheoLab.

 

 
 

Acknowledgements

 

This work was supported by Marie Curie Initial Training Network: SOMATAI (“Soft Matter at Aqueous Interfaces”).

 

 

 

Learn more about Marie Curie Initial Training Network: SOMATAI (“Soft Matter at Aqueous Interfaces”).

 
 

References

 

[1]   D.A. Weitz, and D.J. Pine, Diffusing-Wave Spectroscopy. In Dynamic Light Scattering; Brown,W., Ed.; Oxford University

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[2]   Petr Stern, Helena Valentová, Jan Pokorny, Rheological properties and sensory texture of mayonnaise, J. Lipid Sci.

        Technol., 103 (2001).

[3]   Wendin, K. Aaby, K. Edris, A. Ellekjaer, M. P. Bergenstahl, B. Johansson, L. Willers, E. P. Solheim, Low-fat mayonnaise:

        influences of fat content, aroma compounds and thickeners. Food Hydrocolloids, 11 (1997).

[4]   Hou-PinSu, Chuang-Ping Lien, Tan-Ang Lee and Ruo-Syuan Ho, Development of low-fat mayonnaise containing

        polysaccharide gums as functional ingredients, J Sci Food Agric, 90 (2010),

[5]   K.v Gruijthuijsen, H. Vishweshwara, R. Tuinier, P. Schurtenberger, and A. Stradner, Origin of suppressed demixing in

        casein/xanthan-mixtures, Soft Matter, 8 (2011).

 

 

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