Enrichment of the conjugated linoleic acid content of bovine milk fat by dry fractionation

This study investigated the effect of fat fractionation on the conjugated linoleic acid (cis-9, trans-11-C-18 : 2) content of bovine milk fat. Anhydrous 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 0.58 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 polyunsaturated 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. Refractionation of the soft fraction did not increase the yield of conjugated linoleic 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 reported. 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 ranged 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 milk fat-containing products. This study highlights that a milk fat fraction enriched in conjugated linoleic acid may be achieved by dry fractionation. (C) 2000 Elsevier Science Ltd. All rights reserved.