Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
2.2.4.3 Crystallisation of edible oils and fats
Crystallisation of edible oils and fats, also called fractionation, is based on the principle that the
solubility of the higher melting components in the liquid phase change at different temperatures.
This difference can be extended by using an organic solvent which has the effect of decreasing
the viscosity and leading to better washing of the crystals.
The equipment includes tanks for preheating; stirred and cooled tanks for crystallisation; band
or membrane filters for the separation of the crystals from the liquor and distillation vessels for
solvent recovery. The oil is heated to 10 ºC above the melting point of the highest
triacylglycerol present, to give a fully liquid starting material, e.g. the heating point is typically
75 ºC for palm oil. The molten oil is then cooled and stirred to form crystal nuclei, and the
temperature is maintained at a lower temperature to induce crystal growth, typically for
12 hours at 28 – 30 ºC for palm oil. If a solvent is used, it is added to the molten oil prior to
cooling. The mixtures containing the crystallised solids and the dissolved liquids are separated
by filters. If a solvent is used, it is removed from the fractions by distillation.
2.2.4.4 Further processing of edible oils and fats – margarine
The main products manufactured from edible oils and fats are margarine, edible fats, edible oils
and mayonnaise. In view of its major outstanding importance, only margarine production is
described here.
Most installations carry out hydrogenation to produce fats with superior retention qualities and
higher melting points. Hydrogenation is usually carried out by dispersing hydrogen gas in the
oil, in the presence of a finely divided nickel catalyst supported on diatomaceous earth. The
resultant hydrogenated fats are filtered to remove the hydrogenation catalyst, subjected to a light
earth bleach and deodorised before they can be used for edible purposes. After hardening, the
oil is mixed with an aqueous solution to produce an emulsion. The emulsified mixture is then
pasteurised, cooled and crystallised to obtain the final product.
2.2.4.5 Olive oil
The words “olive oil” mean the product obtained from Olea europea. It is composed of
about 98 % glycerides with the remaining 2 % being various components naturally present in
olives, some of which play a fundamental role in the olfactory and taste characteristics and
which are also important for the stability and quality of the product. Olive oils and husk oils are
classified on the basis of denominations and definitions from Regulation 136/66/EEC of
22 September 1966 on the establishment of a common organisation of the market in oils and
fats [215, EC, 1996].
Extra virgin oils, virgin oils and ordinary virgin oils are edible; yet only extra virgin oils and
virgin oils can be commercialised as they are for direct consumption. Ordinary virgin oils are
commonly used mixed with refined olive oils and refined husk oils. Acid oils with an acidity
higher than 3.3 degrees must be refined.
The quality of the olive oil depends on the ripeness of the olives, the type of harvesting, e.g.
picking or shaking, the type of intermediate storage, and the type of processing carried out.
Olives contain 38 to 58 % oil and up to 60 % water. Ripe olives should be processed as quickly
as possible since lipases in the pulp cause rapid hydrolysis of the oil, impairing its quality for
edible purposes. Top-grade oils are made from fresh, handpicked olives by size reduction,
pasting, and cold pressing. In the production of olive oil, there are three systems currently in use
for the extraction of the oil; traditional, by pressing; three-phase separation or two-phase
separation.
78 January 2006 RHC/EIPPCB/FDM_BREF_FINAL