Food Emulsifiers and Stabilizers - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 213

When the only hydrophilic group present is ethylene oxide, and also for ethylene
oxide derivatives, this reduces to HLB = E/5. The W/O type emulsion will have a
low HLB of 4 to 6, an O/W emulsion has an intermediate HLB of 8 to 15, and a
solubilizing agent has a high HLB of 15 to 18. Several methods have been proposed
to determine the HLB of nonionic surfactants 32 and tables with the HLB values are
available in any surfactant science textbook. Moore and Bell 32 suggested the H/L
value. Greenwald et al. 33 suggested a water titration procedure (the water numbers)
of organic solution of surfactant, but the method has not been widely used. Davies 34
developed a method for calculating the HLB values of surfactants directly from their
chemical formula, using empirically derived group numbers.

HLB = Σ Hydrophilic group numbers - Σ Lipophilic group numbers

They gave the values of the group numbers in a single table and the match
between this method of evaluation of HLB and the empirical work is quite good.
The experimental determination of the HLB of a surfactant is not an easy task.
The HLB concept is based on a simplified picture of the coalescence and
formation process, and does not take into account the important role of liquid-film
thinning between droplets and the importance of shear and dilution properties of the
adsorbed layer of the surfactant around the droplets. Therefore, it is not surprising
that the literature is full of examples of emulsifications that do not obey the HLB
concept. While the validity of the HLB has been criticized, nevertheless it can be a
very useful concept in the formulation of emulsions. In practice, in formulating an
emulsion one must determine, with a set of known emulsifiers, the required HLB
of a given oil used for the preparation of the emulsion (by defining the minimum
oil separation at given conditions and constant concentration of a set of known
emulsifiers). Many of the common oils have required HLB values given in tables.
For any new emulsion to be prepared, the best set of emulsifiers will be determined
on the basis of the required HLB and the minimum oil separation after storage. The
HLB values are additive and can be easily calculated for a set of two nonionic
emulsifiers.
Shinoda and co-workers 35-38 devoted many years of research to find better con-
cepts to describe the relationship of the surfactant structure, its solubility, and the
emulsification parameters. Concepts such as phase inversion (PIT), HLB numbers,
and emulsion inversion point (EIP) were introduced and phase diagrams constructed.
The Shinoda concepts have a sound thermodynamic basis and explain many of the
phenomena attributed to the nonionic emulsifiers.
Typical examples of food emulsifiers are propylene glycol monostearate, which
is strongly lipophilic with an HLB of 3.4; polyoxypropylene stearate with an HLB
of 8; polyoxyethylene monostearate which is less lipophilic (more hydrophilic) with
an HLB greater than 11. HLB values of the many different types of food grade
emulsifiers have been given by Griffin 30,31 and Petrowski. 39
HLB values can be very useful for selecting an appropriate emulsifier, preparing
an emulsion, or for blending several emulsifiers to achieve a desired HLB value.
These HLB numbers are algebraically additive calculations which work well when
a given formula is composed of water and oil-type food emulsions or esters of