Biomedical Engineering Reference
In-Depth Information
A recently identified food contaminant, 3-chloropropane-1,2-diol (3-MCPD-esters) is
formed from glycerol or acylglycerols and chloride ions. For refined vegetable oils the
average content of 3-MCPD-esters increases in the order rapeseed oil, soybean oil, sunflower
oil, safflower oil, walnut oil to palm oil. Deodorization was clearly identified as the critical
step in the formation of 3-MCPD-esters (Weißhaar, 2008). It appears that a significant
reduction of 3-MCPD-esters in foods is not simple but current research and development
efforts are expected to bring solutions to this issue.
4.4.5 Winterization
Winterization is a separation process by which higher melting point acylglycerides and
waxes, which are responsible for the turbidity of some edible oils at cold temperatures, are
crystallized and removed (Leibovitz and Ruckenstein, 1984). Composition of the oil, rate of
cooling, temperature of crystallization and mobility of TAG molecules in the oil are critical
factors affecting efficiency of winterization. These factors play a significant role both in
formation of the solid phase and then separation of the solids from the liquid portion. The
edible oil industry utilizes the liquid fraction to make high quality salad oils whereas the
solid fraction is used in shortening or margarine formulations. During the winterization
process, the oil is cooled from room temperature to a predetermined temperature of
crystallization. The cooled oil is kept at this temperature for a certain period prior to the
separation of solid phase from the liquid oil by filtration of the oil-solid fat slurry. In a
winterization process, cooling rate and temperature of crystallization are extremely
important. Too low a temperature and high cooling rates will result in high viscosity and
reduce crystal growth rate. A mild agitation is recommended to provide a gentle motion to
the crystals to enhance their growth rate and keep the temperature and composition uniform
in the bulk oil. The agitator design should be such that no shear to break the crystals is
generated. In commercial winterization operations crystal modifiers or an appropriate
solvent are used to facilitate filtration of solid phase from the liquid oil.
The presence of high concentrations of waxes and mucilagenous materials in the oil
makes winterization of some oils difficult. In such cases filtration of the oil is hindered by
the high viscosity of the cold oil, the lack of uniformity in crystal formation of the waxes,
and the presence of mucilaginous materials which coat the wax crystals (Morrison and
Robertson, 1975). Washing crude oil with emulsifiers removes waxes and the majority of
PLs and helps with the subsequent winterization process. Solvent winterization from acetone
or an 85/15 acetone-hexane mixture is shown to be effective in peanut and sunflower oil
winterization by reducing viscosity. In addition, small amounts of diatomaceous earth
addition increased the filtration rate of cold sunflower seed oil by a factor of four.
4.5 CONCLUSIONS
The oil and oilseed processing industry has gone through many changes over the last two
decades. Major developments in the industry have been technical improvements in unit
operations and equipment. Changes in technology have been in reaction to the more strict
environmental regulations imposed on processors, industry consolidation, consumer
awareness and agricultural and biotechnical advances. Liquid or solid waste generated
during oil and oilseed processing has always been a major concern. Today solvent emissions
and waste disposal, that is spent bleaching clay, waste water, soapstock and deodorizer
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