2009_Book_FoodChemistry

8.15 Surface-Active Agents 459
Cubic: Cubic space- and face-centered water aggregates
in a matrix of emulsifier molecules; the
polar groups are oriented towards the water.
Phase diagrams show the mesophase present as
a function of water content and temperature.
In the phase diagram of the o/w emulsifier
lysolecithin (Fig. 8.17, a), micelles, a lamellar,
and a hexagonal phase appear. The w/o emulsifier
1-monoelaidin (Fig. 8.17, b) crystallizes at
Fig. 8.18. Ternary phase diagram for the system monoglycerides
(from sunflower oil)/water/soybean oil at
40 ◦ C (according to Larsson and Dejmek, 1990)
1 Microemulsion, 2 Cubic, 3 Hexagonal II, 4 Lamellar
temperatures below 30 ◦ C. The β-modification
formed first is converted to the more stable
β-form, which unlike the α-form, has no emulsifying
properties. The melted 1-monoelaidin
forms a microemulsion with little water and
lamellar and cubic mesophases with much water.
1-Monoolein (Fig. 8.17, c) melts at lower temperatures
and an inverse hexagonal mesophase
appears.
The phases of simply constituted food emulsions,
which are present at a certain temperature depending
on the composition, show a ternary phase
diagram, e. g., in Fig. 8.18.
8.15.2.3 HLB-Value
Fig. 8.17. Binary phase diagrams for the system emulsifier/water
(according to Krog, 1990) (a) Lysolecithin,
(b) 1-Monoelaidin, (c) 1-Monoolein
1 Crystals, 2 Micelles, 3 Microemulsion, 4 Hexagonal I,
5 Lamellar, 6 Hexagonal II, 7 Cubic
A tenside with a relatively strong lipophilic group
and weak hydrophilic group is mainly soluble
in oil and preferentially stabilizes a w/o emulsion,
and vice versa. This fact led to the development
of a standard with which the relative
strength or “activity” of the hydrophilic and
lipophilic groups of emulsifiers can be evaluated.
It is called the HLB value (hydrophilic–lipophilic
balance). It can be determined, e. g., from dielectric
constants or from the chromatographic behavior
of the surface-active substance. The HLB
value of the fatty acid esters of polyhydroxy alcohols
can also be calculated as follows (SV =