15
Crystallization
Crystals are often formed in foods and during food processing. It concerns
ice, sugars, salts, triacylglycerols, and other, generally minor, components.
Crystallization can have large effects on food properties, especially on
consistency, mouth feel, and physical stability. Crystallization is mostly
preceded by nucleation, which is discussed in Chapter 14. Effects on
consistency are given in Chapter 17. Freezing of foods, i.e., freezing most of
the water in a food, has several ramifications; it is the main subject of
Chapter 16.
We will only consider ‘‘true,’’ i.e., solid and three-dimensional,
crystals. Liquid crystalline phases can be formed in aqueous solutions of
some amphiphilic molecules (briefly mentioned in Section 10.3.1), and some
materials in a densely packed adsorption layer can attain a two-dimensional
crystalline order. Unless mentioned otherwise, crystallization from solution
is implied in this chapter.
15.1 THE CRYSTALLINE STATE
Order. A crystal consists of a material in a solid state in which the
building entities—molecules, atoms or ions—are closely packed so that the
free energy of the material is at minimum. To achieve this, all of the entities