Emulsifiers in Food Technology
Emulsifiers in Food Technology
Introduction to Food Emulsifiers and Colloidal System
Palsgaard A/S, Palsgaard vej 10, DK-7130 Juelsminde, Denmark
This chapter provides a short introduction to the most important parameters involved in multiphase system. As an introduction, the forces that interact between individual molecules are briefly mentioned, followed by a short review of the factors responsible for formation of, and stability of, systems consisting of two or more incompatible phases, as illustrated by emulsions and cake batters. This illustrates how forces related to amphiphilic substances like food emulsifiers on a molecular level can be thought of as complex foods, or how models of food can be formulated and described to get an idea of how food emulsifiers can act in the complex food and benefit from the emulsifiers. For monographs dealing extensively with interface chemistry see, for example, Israelachivili  or McClements .
Food and food ingredients are made up of a huge number of different types of molecules, and most foods will be amalgamates of numerous different constituents, ranging from small-sized molecules to much bigger biopolymers, altogether forming the compounded food. This means a substance or individual component will be associated with a number of similar, as well as different, substances, and together they will give the food its texture, sensory and other characteristics. In the food or food ingredient, individual components can be present in various forms-either in similar constituents, or as a mix of discrete components. Often, they will be organized into separate structural entities at the interface between different phases, or may be dispersed as separate accumulated bodies or aggregates in a bulk phase. The food components can also be elements of a internal three-dimensional lattice, forming an integrated structure and thus giving the food the characteristic physical and chemical properties recognized as texture and organoleptic profile.
This means that the properties of food originate from the substances present. Due to intermolecular interactions and forces combined with external factors like temperature, stress, etc. they combine into structural organizations like dispersions, foams, emulsions, gels and other composite systems.
At the molecular level, individual molecules will interact due to a number of attractive as well as repulsing forces see Table 1.1 page 3 between the molecules. These forces are recognized as Van der Waal forces and, compared to intramolecular forces (i.e. covalent bonding), are approximately two decades weaker. However, although weak, they play and important role when considering interaction within neighbour compounds. The Van der Wall forces can be classified into three distinct groups: Orientation forces, Debye forces and London forces.
Table 1.1 Some molecular and intermolecular forces.
Type Energy Ratio vs distance Type of forces Covalent <120 kJ 1/r (strong) electrons are shared Electrostatic 40-90 kJ 1/r (strong) ion-ion, ion-dipole, dipole-dipole Hydrogen bonds 6-25 kJ 1/r6 (weak) dipole-dipole + van der Waal Van der Waal 2-10 kJ 1/r6 (weak) induction, rotation, dispersion
The first of these, i.e. the orientation forces, take their onset from electrostatic interaction arising from unsymmetrical charge distributions within electrically neutral molecules-a charge displacement causing a permanent dipole moment. The presence of a permanent dipole moment will induce an electrostatic int