Agriculture Reference
In-Depth Information
Fractionated milkfats
Fractionated milkfats may be made by different methods, but the most commonly
used and preferred method is that of dry fractionation: so called because it does
not involve solvent extraction. Dry fractionation processing is considered in detail
by Deffense (2000), Gibon (2002) and Timms (2005). The dry fractionation
process is based on 'winterisation', which Gunstone (2008) recognises as a simple
process in which, for example, cottonseed oil stored in tanks in winter allows the
high-melting point triacylglycerols to crystallise such that the liquid low-melting
point fraction can be drawn off for domestic use including storage in refrigerators.
The phenomenon of differential fat crystallisation at low temperature is seen in
olive oil kept in cold kitchens.
In the production of fractionated milkfats, AMF or butteroil is heated above
75°C in a temperature-controlled jacketed vessel to ensure that all triacylglycerols
are completely melted. Pure stearic acid has a melting point of 73°C. The stepwise
reduction in temperature with carefully controlled agitation of the oil causes fi rst
the crystallisation of the higher melting point fractions. The crystallised fats and
liquid oil are pumped from the jacketed vessel through a vacuum fi lter which
separates the hard fat fraction from the oil, which is returned to the vessel. Further
controlled reductions in temperature coupled with fi lter separations yields fractions
ranging from those that are solid at room temperature (stearins) to those that are
liquid at room temperature (oleins) and even under refrigeration. In contrast to
fractions made from simpler vegetable oils such as palm oil, the complexity of
tiacylglycerols in milkfat results in fractions which when close together in the series
do not exhibit distinctly different functional properties (Gunstone 2008). As milkfat
is fractionated, the
β
-carotene is partitioned with the olein fraction which obtains a
golden-yellow colour in contrast to the hardest fractions which are almost white.
AMF and butteroil are used as ingredients in many foodstuffs worldwide. A
common use is in recombined milk products where milkfat is combined with NFMS
to make a variety of dairy products, including milk, evaporated milk, sweetened
condensed milk, cream and cheese. Both are used in catering and industrial
processing as a heat transfer medium and as an ingredient in product manufacture.
In industrial food manufacture, AMF and butteroil are used widely in yellow-fat
spreads, ice cream, confectionery (e.g. toffees and caramels) and bakery applications.
Fractionated milkfats are used in confectionery and baked goods manufacture. The
hard fractions are used predominantly in laminated and puff pastries where they aid
lift during cooking and help to retain structure by crystallising quickly as products
cool. The soft fractions, which are rich in colour and fl avour, are used in
confectionery. Milkfat fractions can also be of benefi t in chocolate, where they
bring consistency to texture, hardness, gloss, snap and mouthfeel.
17.5 Future trends
Trends in relation to dairy products in which natural additives, ingredients and
fl avourings are used and in relation to the use of dairy products as natural additives,
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