Abstract: Egg yolk oil is a concentrated source of egg bioactive compounds, such as fat-soluble vitamins, phospholipids, cholesterol, carotenoids and others. To extract lipids and other fat-soluble nutrients from liquid egg yolk, a two-step extraction process involving polar (ethanol) and non-polar (hexane) solvents were used. This extraction technique was based on egg yolk bioactive compounds polarities, where non-polar compound was extracted into non-polar hexane, but polar in to polar alcohol/water phase. But many egg yolk bioactive compounds are not strongly polar or non-polar. Egg yolk phospholipids, cholesterol and pigments are amphipatic (have both polar and non-polar regions) and their behavior in ethanol/hexane solvent system is not clear. The aim of this study was to clarify the behavior of phospholipids, cholesterol and carotenoids during extraction of egg yolk oil with ethanol and hexane and determine the loss of these compounds in egg yolk oil. Egg yolks and egg yolk oil were analyzed for phospholipids (phosphatidylcholine (PC) and phosphatidylethanolamine (PE)), cholesterol and carotenoids (lutein, zeaxanthin, canthaxanthin and β-carotene) content using GC-FID and HPLC methods. PC and PE are polar lipids and were extracted into polar ethanol phase. Concentration of PC in ethanol was 97.89% and PE 99.81% from total egg yolk phospholipids. Due to cholesterol’s partial extraction into ethanol, cholesterol content in egg yolk oil was reduced in comparison to its total content presented in egg yolk lipids. The highest amount of lutein and zeaxanthin was concentrated in ethanol extract. The opposite situation was observed with canthaxanthin and β-carotene, which became the main pigments of egg yolk oil.
Abstract: Egg yolk oil is a natural source of bioactive
compounds such as unsaturated fatty acids, oil soluble vitamins,
pigments and others. Bioactive compound content in egg yolk oil
depends from its content in eggs, from which oil was extracted. Many
studies show that bioactive compound content in egg is correlated to
the content of these compounds in hen feed, but there is also an
opinion that hen housing systems also have influence on egg
chemical content. The aim of this study was to determine which
factor, laying hen housing system or hen diet, has a primary influence
on bioactive compound content in egg yolk oil. The egg yolk oil was
extracted from eggs obtained from 4 different hen housing systems:
cage, barn and two groups of free range. All hens were fed with
commercially produced compound feed except one group of free
range hens which get free diet – pastured hens. Extracted egg yolk
oils were analyzed for fatty acids, oil soluble vitamins and β-carotene
content. α-tocopherol, ergocalcipherol and polyunsaturated fatty acid
content in egg yolk oil was higher from eggs obtained from all
housing systems where hens were fed with commercial compound
feed. β-carotene and retinol content in egg yolk oils from free range
free diet eggs was significantly (p>0.05) higher that from other eggs
because hens have access to green forage. Hen physical activity in
free range housing systems decreases content of some bioactive
compound in egg yolk oil.