Food Chemistry

8.15 Surface-Active Agents 459

Cubic: Cubic space- and face-centered water ag-
gregates 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 emulsi-
fier 1-monoelaidin (Fig. 8.17, b) crystallizes at

Fig. 8.17.Binary phase diagrams for the system emul-
sifier/water (according toKrog, 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

Fig. 8.18.Ternary phase diagram for the system mono-

glycerides (from sunflower oil)/water/soybean oil at

40 ◦C (according toLarssonandDejmek, 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 theα-form, has no emul-

sifying 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 tem-

peratures and an inverse hexagonal mesophase

appears.

The phases of simply constituted food emulsions,

which are present at a certain temperature de-

pending on the composition, show a ternary phase

diagram, e. g., in Fig. 8.18.

8.15.2.3 HLB-Value

A tenside with a relatively strong lipophilic group

and weak hydrophilic group is mainly soluble

in oil and preferentially stabilizes a w/o emul-

sion, and vice versa. This fact led to the de-

velopment of a standard with which the rela-

tive strength or “activity” of the hydrophilic and

lipophilic groups of emulsifiers can be evaluated.

It is called theHLB value(hydrophilic–lipophilic

balance). It can be determined, e. g., from dielec-

tric constants or from the chromatographic be-

havior of the surface-active substance. The HLB

value of the fatty acid esters of polyhydroxy al-

cohols can also be calculated as follows (SV =