- Agitation. This has a strong effect, as illustrated in frame (b). The
following mechanisms play a part. (a) The encounter frequency is
proportional to the velocity gradient (shear rate) C. For some systems
nearly the same holds for the aggregation rate: see curve 1. (b) The chance
that a protruding crystal does indeed reach the film between two globules is
greatly enhanced by the globulesrollingover each other, as they do in a
shear field: see Figure 13.20b. The effect is substantial, but it does not
depend on the magnitude ofC. (c) Generally, the globules repel each other,
FIGURE13.21 Effect on the rate of partial coalescence (Q) in protein-stabilized
O–W ‘‘emulsions’’ of the variables: (a) volume fraction (j); (b) shear rateðC=s^1 Þ;
(c) globule diameter (d/mm); (d) fraction of the fat being solid (jS); (e) protein surface
loadðG=mg?m^2 Þ; and (f) concentration of small-molecule surfactant added (c/%).
Only meant to illustrate trends. In some frames results for different systems are
shown.