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A viscometric study of the flocculation of the components in stored homogenized ultra-heat-treated cream

Published online by Cambridge University Press:  01 June 2009

Leslie W. Phipps
Leslie W. Phipps
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading RG2 9 AT, UK
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Summary

The apparent relative viscosity (ηr) of stored homogenized ultra-heat-treated ‘coffee’ cream increased with time (t) at a rate which was a function of mean fat globule diameter (d) and fat volume fraction (ø); the rate was also influenced by Na2CO3 and Na citrate when present as stabilizing additives. Viscosity increases were attributed to the progressive flocculation of fat globules and to the strengthening of the structure formed by the gradual accretion of casein micelles on to globule surfaces and their points of contact (bridging). The expression

where t is in days and d in μm, was found to hold over a 12-week storage period for a batch of creams (ø = 0·143) of different d values prepared from the bulk cream containing carbonate and citrate stabilizers; η0 is the relative viscosity at t = 0 and k is a rate parameter. In the absence of stabilizers the parameter k assumed a smaller value and so appeared to be a function of chemical composition of the cream and of forces of particle interaction; seasonal factors were also suspected of influencing k. The effect of the fat volume fraction on storage behaviour was not fully resolved, but there was some evidence that the proportionality log ηrα1/ø½ was appropriate.

Type
Original Articles
Information
Journal of Dairy Research , Volume 49 , Issue 4 , November 1982 , pp. 655 - 664
Copyright
Copyright © Proprietors of Journal of Dairy Research 1982

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References

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