INCORPORATION OF POLYUNSATURATED FATTY-ACIDS IN EGG-YOLK FAT AT VARYING DIETARY-FAT LEVELS AND COMPOSITIONS

One feeding trial was conducted to study the effects of different diet ary levels (0-3-6-9%) and combinations of lard, soybean oil, and flax seed oil on the fatty acid composition of the egg yolk lipid. Special attention was given to the compositional stability of these fats. The results were evaluated by response surface modeling. 2. The apparent d eposition rate of total lipid and fatty acids as well depended on both the dietary level and the metabolic pathway of the fatty acids (de No vo synthesis, rate of transfer,...). 3. The U/S-ratio of the yolk fat varied from 2.0 to 3.1. The major changes in yolk fatty acids were wit hin the C18-unsaturates, whereby changes in C18-PUFAs were balanced by proportional changes in oleic acid. The results indicated no de novo synthesis for the C18-PUFAs. The maximum incorporation levels for lino leic and linolenic acid were 33.5 and 19.8%, respectively. The omega-6 /omega-3-ratio's of the yolk Eat were obviously higher than those of; the respective dietary fat combinations. 4. No differences in sensory characteristics were observed.