Physical Chemistry of Foods

15 Crystallization Crystals are often formed in foods and during food processing. It concerns ice, sugars, salts, triacylglycero ...

have to be subject to the same interaction forces (magnitude and direction), i.e., be in the same environment. As a result the e ...

FIGURE15.1 Two-dimensional illustration of crystalline order. (a) Example of a crystal lattice with perfect order. (b) Example o ...

the water molecules present allow a closer packing and/or a greater number of hydrogen bonds. Crystal Systems. To understand sev ...

illustrated in Figure 15.3, which gives theprimitive cells, i.e., only the shape; the number of Bravais lattices in each system ...

FIGURE15.3 Crystal systems. Shown is the shape of the unit cell for each system, the number N of different Bravais lattices in e ...

envisaged. Hence, cubic crystals can have angles between faces that do not equal 90 8 but also, for instance, 135 8. The angles ...

value is indicated by a dash above the number). If a crystal has a face (110), it likely also has the facesð 110 Þ,ð 110 Þ,andð ...

Compound Crystals. Several molecular crystals contain more than one component. Substances crystallizing with solvent (mostly wat ...

Question Does the absence of certain crystal faces necessarily imply that such faces do not grow at all? Answer No. It can also ...

supersaturation. According to Eq. (15.1) the supersaturation ratio b ¼ a/aeq, but it is usually taken asc/ceq, wherecis concentr ...

Thermodynamic Roughening. A crystal in a solution that is precisely saturated may have faces that are not flat and smooth on a m ...

faster than at a smooth surface for a given supersaturation. The sticking probability of a molecule at a smooth surface is small ...

connected-network theory) from the various crystal bond energies, if they are known. It follows thatDG* will generally be differ ...

growing sucrose crystals. The spirals greatly enhance crystal growth rate. A calculated curve (S) is in Figure 15.6 (the calcula ...

consequence is that the face does not remain flat on amm scale, but becomes curved(convex). For most crystal faces a very high s ...

Crystallization Regime. This has been discussed in the previous section. It should be realized that properties of the crystal pr ...

about perpendicular to the surface, this misorientation causes an additional decrease in growth rate. This may be the main reaso ...

Competition. It often happens that some kinds of ‘‘foreign’’ molecules fit more or less in a vacant site in the crystal. These m ...

low supersaturation. It has a very strange shape. The crystal has started to grow at the apex i.e., at the top in the picture, a ...