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Rheology of milk foams produced by steam injection

Jimenez Junca, C. A., Gumy, J. C., Sher, A. and Niranjan, K. (2011) Rheology of milk foams produced by steam injection. Journal of Food Science, 75 (9). E569-E575. ISSN 1750-3841

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To link to this article DOI: 10.1111/j.1750-3841.2011.02387.x

Abstract/Summary

Rheology of milk foams generated by steam injection was studied during the transient destabilization process using steady flow and dynamic oscillatory techniques: yield stress (τ_y) values were obtained from a stress ramp (0.2 to 25 Pa) and from strain amplitude sweep (0.001 to 3 at 1 Hz of frequency); elastic (G') and viscous (G") moduli were measured by frequency sweep (0.1 to 150 Hz at 0.05 of strain); and the apparent viscosity (η_a) was obtained from the flow curves generated from the stress ramp. The effect of plate roughness and the sweep time on τ_y was also assessed. Yield stress was found to increase with plate roughness whereas it decreased with the sweep time. The values of yield stress and moduli—G' and G"—increased during foam destabilization as a consequence of the changes in foam properties, especially the gas volume fraction, φ, and bubble size, R_32 (Sauter mean bubble radius). Thus, a relationship between τ_y, φ, R_32, and σ (surface tension) was established. The changes in the apparent viscosity, η, showed that the foams behaved like a shear thinning fluid beyond the yield point, fitting the modified Cross model with the relaxation time parameter (λ) also depending on the gas volume fraction. Overall, it was concluded that the viscoelastic behavior of the foam below the yield point and liquid-like behavior thereafter both vary during destabilization due to changes in the foam characteristics.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Food and Nutritional Sciences > Food and Bioprocessing Research Group
ID Code:27485
Publisher:Wiley
Publisher Statement:Practical Application: Studying the transient rheology of milk foams during destabilization contributes to our knowledge of the relationships between the changes in foam properties: texture and mouth feel during the consumption of hot foamed beverages.

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