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Measurement of electrophoretic mobilities and zeta-potentials of particles from milk using laser Doppler electrophoresis

Published online by Cambridge University Press:  01 June 2009

Douglas G. Dalgleish
Douglas G. Dalgleish
Affiliation:
Hannah Research Institute, Ayr, Scotland KA6 5HL
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Summary

The use of a commercial laser Doppler electrophoresis apparatus to measure electrophoretic mobilities of milk constituents is demonstrated, and calculations of apparent ζ-potentials from these mobilities are given. Systems studied were: native and renneted casein micelles suspended in milk ultrafiltrate and different buffers containing Ca2+, particles from homogenized milk before and after renneting, fat globules, and homogenized fat/caseinate systems. The results confirmed previous estimates of the ζ-potentials of these materials, but also extended to cover the effect of changing the concentrations of Ca2+ and other salts on the electrokinetic properties of the particles. Increasing concentration of Ca2+ caused considerable decrease in the ζ-potentials of native and renneted casein micelles, and temperature increase caused the apparent ζ-potential to increase in both cases. Particles from homogenized milk showed ζ-potentials very similar to those of native casein micelles, and renneting of the homogenized milk gave behaviour similar to renneted casein micelles. The ζ-potential of the homogenized materials could be distinguished clearly from those of native fat globules. Likewise, milk fat which had been homogenized using whey protein showed distinct differences in its surface properties from particles based on caseinate or casein micelles.

Type
Original Articles
Information
Journal of Dairy Research , Volume 51 , Issue 3 , August 1984 , pp. 425 - 438
Copyright
Copyright © Proprietors of Journal of Dairy Research 1984

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