Physical refining was originally developed for high(er) FFA oils (such as palm
oil) for which chemical refining is not economically attractive. Physical refining
results in more easily valorised side products (e.g. deodoriser distillate), but
generally requires better quality crude oil. It is therefore more suitable for
integrated crushing–refining plants with better control over the incoming
crude oil quality.
The broader industrial application of physical refining first requires an
efficient degumming process that can ensure a very good degummed oil
10 ppm) even when applied to lower quality crude (soft) oils.
The traditional classification of phospholipids into so-called hydratable
and nonhydratable components is well known in the literature. Hydratable
phospholipids can easily be removed during water degumming, which is
generally applied as first refining step in the oilseed extraction plant. The
resulting gums can either be added back to the deoiled meal or valorised
separately as lecithin.
Nonhydratable phospholipids are removed during so-called acid degum-
ming. This is usually the first stage of physical refining and can be considered
the equivalent process to alkali neutralisation in chemical refining. Important
developments in acid degumming date from the 1980s, driven by the first real
interest in physical refining. New features such as improved dosing systems,
more powerful mixing systems (to get finer dispersion of the degumming
acid), addition of caustic and oil cooling for gum hydration were successfully
implemented and resulted in a significant improvement in degumming effi-
ciency. Processes such as TOP degumming (Vandemoortele) and Super- and
Uni-degumming (Unilever), which are still used today in edible oil refining,
were developed during that period.
First-generation enzymatic degumming (Enzymax process), soft degum-
ming (Tirtiaux) and membrane degumming (Cargill, Desmet) were developed
in the 1990s. The need for a milder but still efficient degumming process
requiring less chemicals was the main driver. Unfortunately, these degum-
ming processes were never broadly implemented on an industrial scale.
Miscella membrane degumming (Lin & Koseoglu, 2004) was applied indus-
trially for a short time but was soon abandoned due to excessive problems
with irreversible membrane fouling. Industrial application of soft degumming
(Deffense, 2002) was hindered by the fact that ethylenediaminetetraacetic
acid (EDTA) was used as a chelating agent, which raised some acceptability
issues. The main drawbacks of the Enzymax process (Clausen, 2001) were the
high enzyme cost, the relatively poor stability and selectivity of the enzyme
and the fact that a porcine pancreas lipase was used.
A renewed interest in enzymatic degumming has been observed in recent
years. This is mostly due to the commercial availability of several new, cost-
efficient and stable phospholipases with sufficiently high enzyme activity,
developed and guaranteed by various suppliers (Table 5.1). In addition, there
is the new market approach of the enzyme producers, who no longer present
enzyme degumming as an efficient degumming process but rather as a process
that results in a significantly higher refined oil yield. With the current high
edible oil prices, oil refiners are very sensitive to this feature, making it the
most important driver for the wider application of ‘new-generation’ enzymatic
Current commercial phospholipases are all of microbial origin. Their mode
of action is illustrated in Figure 5.2. Phospholipase A1 (PL-A1, e.g. Lecitase
Ultra from Novozymes) and phospholipase A2 (PL-A2, e.g. Rohalase MPL
from AB Enzymes, GumZyme from DSM) both release a fatty acid from
the phospholipid molecule, resulting in a lysophospholipid and an FFA.