Question
A food company makes a product that is an oil-in-water emulsion. To check on its
physical stability, a sample of each day’s production is stored overnight in a
thermostat and it should then not show visible creaming. One day, significant
creaming is observed. Make a list of the possible causes and also give the methods
used to establish which of the possibilities was the real cause.
BIBLIOGRAPHY
Most texts on colloid science give ample information on some of the changes
discussed, especially on aggregation. The classical treatment of aggregation kinetics
still is
J. T. G. Overbeek. Kinetics of flocculation. In H. R. Kruyt, ed. Colloid Science.
Vol. I. Irreversible Systems. Elsevier, Amsterdam, 1952, Chapter 7.
A monograph on various aspects of aggregation is
K. J. Ives, ed. The Scientific Basis of Flocculation. Sijthoff and Noordhoff, Alphen
aan de Rijn, 1978.
Especially the chapters by Ives on rate theories (pp. 37–61) and by L. A. Spielman on
hydrodynamic aspects of flocculation (pp. 63–88) are recommended. An extensive
and detailed treatment is in
T. G. M. van de Ven. Colloidal Hydrodynamics. Academic Press, London, 1988.
This especially stresses the hydrodynamic aspects of aggregation and coalescence. An
overview of fractal aggregation is
P. Meakin. Fractal aggregates. Adv. Colloid Interface Sci. 28 (1988) 249–331.
The effects on aggregation times of fractal aggregation and of other particulars of the
process are treated by
L. G. B. Bremer, P. Walstra, T. van Vliet. Estimations of the aggregation times of
various colloidal systems. Colloids Surf. A 99 (1995) 121–127.
A discussion on the various types of instabilities in emulsions is
P. Walstra. Emulsion stability. In: P. Becher, ed. Encyclopedia of Emulsion
Technology. Vol. 4. Dekker, New York, 1996, Chapter 1.
Emulsion stability is also treated in
B. P. Binks, ed. Modern Aspects of Emulsion Science. Roy. Soc. Chem., Cambridge,
1998.