Physical Chemistry of Foods

are in Table 12.2. It is seen that the values tend to increase with molar mass for a homologous series and are higher for a crys ...

act except hard-core repulsion. The latter is taken care of by assuming that very strong repulsion prevails below a certain valu ...

less well known; assumingA¼ 4? 10
^21 J, we arrive atpdisj&
210 Pa, i.e., much smaller than for air–water–air. Question 2 W ...

a charge sign opposite to that at the interface) accumulate near the interface, whereas coions (same charge sign as at the inter ...

ions is governed by two opposing effects. The attractive energy between ions of opposite charge pulls the counterions to the sur ...

are closely packed; it is called theStern layer. In practice, however, one may take forc 0 the potential at the Stern layer (see ...

protein, which adsorbs onto the W–O interface, thereby giving rise to a surface charge and thus to a surface potentialc 0. The o ...

longer distances than does double layer repulsion. For two spheres of equal size it is given by VEl;s¼ 4 p[ 0 [R^2 c^20 2 Rþh &a ...

FIGURE12.4 Examples of the colloidal interaction energyVT(in units ofkBT) as a function of interparticle distanceh, calculated a ...

The Hamaker constant does not vary greatly in most of the systems considered (see Table 12.2). Nevertheless, the variation may ...

Complications. Below are some factors of importance: Particle shape. Calculation of the interaction energy works well for perfec ...

film does not rupture, drainage will go on until the net colloidal disjoining pressure in the film equals the mentioned Laplace ...

12.3.1 Steric Interaction Themode of adsorptionof various polymers is illustrated in Figure 10.12. Polymers can also be ‘‘grafte ...

Conformations similar to ‘‘pancakes’’ and ‘‘brushes’’ can also occur for adsorbed polymers. To achieve substantial repulsive act ...

force will act. The repulsive free energy is very large: several timeskBTfor each polymer chain involved, and the number of poly ...

be applied to situations in foods: it needs knowledge of the magnitude of a number of variables, which is generally not availabl ...

interaction, van der Waals attraction is taken into account. The number densitysof polymer molecules at the surface is kept cons ...

If the magnitude ofIis around 0.1 molar, asalted brushcan be obtained. Due to the Donnan effect, discussed in Section 6.3.3, the ...

of the hairs is close to zero, and the brush collapses as predicted. This leads to rapid aggregation. A third cause is the addit ...

repulsion hardly depends on pH or ionic strength but becomes greatly reduced at high temperatures, say over 60 8 C. Question In ...