Physical Chemistry of Foods

sitytends to enhance the aggregation rate somewhat, even for spheres, because the effects of particle size on collision radius a ...

then often diffuse back again after coming so close that it senses significant repulsion. This implies that the particle concent ...

square of the valence. For the data in Figure 13.4, the proportionality would be toz3.5. The results also depend on the absolute ...

illustrates the large effect of ionic strength on the stability of colloids stabilized by electric charge. Hydrodynamic Retardat ...

Note The theory does not apply for fluid particles in the absence of surfactant, where slip occurs at the particle surface; see ...

These relations imply that foru!0 alsoD!0, or in other words the particles would never touch each other. Although the theory bre ...

Reaction-limited aggregation. This occurs ifWis larger than a critical value (of the order of 100?); presumably, the critical v ...

by small-molecule surfactants. If then aggregation will only occur when protein covered patches come very close to each other, t ...

concentrationNwill be
dN dt ¼ 1 2 JorthoN¼ 2 3 d^3 N^2 C¼ 4 p jNC ð 13 : 8 Þ where C is the velocity gradient, which here equa ...

particles. In a situation as in Figure 13.6, position 3, the particles are pressed together, but a moment later, in position 4, ...

whereDris the density difference between particle and continuous phase. Especially for emulsions with droplets over 2mm in diame ...

ongoing aggregation leads to the formation offractal aggregates. Figure 13.7a shows an example: it is seen that the aggregate ha ...

dimensionality.* Actually, the equation should also contain a proportion- ality constant; whenRis taken as the radius of the sma ...

Note This does not imply that the density decreases when going from the center to the periphery of a cluster: that would be inco ...

The clusters formed should not show significantsedimentationbefore they reach the size Rg, since otherwise demixing would occur. ...

structures formed are not truly fractal any more. However, diffusion-limited aggregation is the exception rather than the rule i ...

should now be transformed into Np np ¼ R aeff D ð 13 : 19 Þ Moreover, the value ofDis generally increased, by an amount up to ...

Answer The aggregates formed will be most likely of a fractal nature. The main question is whether sedimentation (creaming) of c ...

may eventually become visible to the eye (1); the volume fraction of particles jdoes not alter. Nearly the same situation arises ...

tvis¼ 63? 107 s&20 years. For case (2), assuming D¼2, we obtain tg¼6300 s& 1 :8 h, i.e., smaller than for case (1) by a ...