This study investigated the effect of fat fractionation on the conjugated l
inoleic acid (cis-9, trans-11-C-18 : 2) content of bovine milk fat. Anhydro
us milk fat was fractionated into hard and soft fractions using controlled
cooling and agitation. Fractionation of milk fat pre-melted at 60 degrees C
using a temperature programme of 33-10 degrees C and a cooling rate of 0.5
8 degrees C h(-1) yielded a soft fraction containing 63.2% more conjugated
linoleic acid (2.22 g 100 g(-1) FAME), which was also enriched in polyunsat
urated fatty acids and vaccenic acid (trans-11-C-18 : 1) compared with the
parent fat. Agitation following fractionation was found to have a negative
effect on the conjugated linoleic acid content of the soft fraction. Refrac
tionation of the soft fraction did not increase the yield of conjugated lin
oleic acid. The conjugated linoleic acid and trans fatty acid content of 26
selected food products ranging in milk fat content from 0 to 100% is repor
ted. Conjugated linoleic acid concentrations ranged from 0 to 16.2 mg g(-1)
fat and were generally lower than the trans fatty acid content which range
d from 0 to 155.7 mg g(-1) fat. Spreads containing vegetable oils contained
higher trans fatty acid and lower conjugated linoleic acid contents than m
ilk fat-containing products. This study highlights that a milk fat fraction
enriched in conjugated linoleic acid may be achieved by dry fractionation.
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