• Food Quality and Culture
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• v.1 no.1
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• pp.6-12
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• 2007

In this study, we examined the effects of egg yolk powder added to flour dough on the lipid oxidation of fried products during storage. The flour dough containing the egg yolk powder (0, 5, and 10%) was fried in sunflower oil at $180^{\circ}C$ for 90 sec. The fried products were then stored at $60^{\circ}C$ for 9 days in the dark. The lipid oxidation of the fried products was evaluated by fatty acid composition, peroxide values (POV), conjugated dienoic acid (CDA) contents, and thiobarbituric acid (TBA) values. The color and phospholipids (PL) contents of the fried products were also determined by colorimetry and high performance liquid chromatography, respectively. The addition of egg yolk powder to the dough decreased the POV, CDA contents, and TBA values of the fried products during storage. Although POV, CDA contents, and TBA values significantly increased in the products without egg yolk powder during storage, little change was observed in the products with egg yolk powder. The PL contents remained relatively constant in the flied products added with egg yolk powder during storage. The lightness and greenness of the fried products decreased, and the yellowness increased, as the storage time increased. The results clearly indicate that the addition of egg yolk powder to the dough improved the lipid oxidative stability of the fried products during storage in the dark, and the PL in the egg yolk might have contributed to the improvements in lipid oxidative stability.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.5
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• pp.860-865
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• 1997

Investigations were performed on the effects of extraction temperature, pressure, time on solubility and selectivity of egg yolk lipid and cholesterol, and color and fatty acid composition of the residue in supercritical carbon dioxide(SC-Co$_2$) extraction. Lipid and cholesterol solubility increased as the increase of Co$_2$ density and was found to strongly depend on the extraction pressure rather than the extraction temperature. The relative concentration of cholesterol in the extract increased with an increase in temperature and decreased with an increase in pressure and extraction time. extraction of dried eg yolk for 3hr at 4$0^{\circ}C$/276 bar removed 46.1% of cholesterol from the residual egg yolk with a yield of 63.2%. SC-Co$_2$ extraction produced a lighter color egg yolk with less redness and yellowness. As the extraction time increased, the resultant residual egg yolk became more saturated with fatty acids. SC-$CO_2$ extraction offers a safe, natural method for removing cholesterol from dried egg yolk.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.6
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• pp.1032-1037
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• 1994

A simple, reproducible , and accurate enzymatic method using a cholesterol assay kit was developed to quantify total cholesterol content in egg yolk. Total egg yolk lipid was extracted with hexane : isopropanol(3 : 2, v/v) mixture. Samples containing various amount of the total lipid(0-3mg) in optically identifical culture tubes were reacted for 10 min in a water bath (37$^{\circ}C$) with the enzyme solution (5ml) from the cholesterol assay kit. Cholesterol content of the reaction mixturesin culture tubes was spectrophotometrically determined by two different ways : (1) using the culture tube as a curvette(designate culture tube method ; CTM) and (2) the quartz cvette containing the reaction mixture transferred from the culture tube (designate standard cvette method, SCM). CTM revealed lower cholesterol content in 0.1-1.0mg lipid sample range that SCM did, but not significant. For more than 2.0mg lipid sample, CTM gave significantly (p<0.01) lower cholesterol content relative to that by SCM, suggesting that SCM give a false positive result from the sample containing more than 2 mg lipid due to the interference of absorbance by lipid dispersed in the reaction solution . Cholesterol content of less than 1.0mg lipid sample by CTM was proportional to the amount of lipid used, but its linear relationship was not seen in more than 2mg lipid sample. Thus, to determine the appropriate lipid amounts (mg) analyzed . A constant level (41$\mu\textrm{g}$/mg) of cholesterol concentration was observed from the sample containing 0.1-1mg lipid. after which the cholesterol level was dropped to less than 41$\mu\textrm{g}$ /mg. Cholesterol concentration in egg yolk samples quantified by CTM was in accordance with that by GC method. These results suggest that CTM is an useful method for the quantification of cholesterol in egg yolk lipid and other lipids as well.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.8
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• pp.1165-1170
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• 2003

A total of 250 laying hens were fed a diet containing 0, 1, 2.5 or 5% conjugated linoleic acid (CLA), and 5% Safflower seed oil (SSO) for 5 weeks, and eggs were collected by week to analyse lipid characteristics of egg yolk. Egg yolk from CLA-fed groups showed significant increase in CLA content with increased CLA in the diet. Dietary CLA also increased the ratio of saturated fatty acids and decreased unsaturated fatty acids in the egg yolk. The proportion of myristic, palmitic, stearic and CLA were increased, while those of oleic, linoleic, linolenic and arachidonic acid were decreased. The cholesterol content in egg yolk was significantly decreased by dietary CLA for 5 weeks feeding. After 7 days of feeding, 5% CLA-fed group showed the lowest cholesterol content in egg yolk. CLAfed groups showed significantly lower 2-thiobarbituric acid-reactive substances (TBARS) values compared to control and SSO-fed group after 14 days of storage. No significant differences in TBARS values among CLA-fed groups were observed at the 28 days of storage. Results suggested that lipid oxidation of egg yolk during cold storage could be inhibited by dietary CLA due not only to changes in fatty acid composition but also to the high concentration of CLA in egg yolk.

• Food Science of Animal Resources
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• v.18 no.4
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• pp.339-347
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• 1998

The effects of conjugated linoleic acid (CLA) in egg yolk on fatty acid composition and lipid oxidation during chilled storage (4$^{\circ}C$) were investigated. CLA was synthesized according to the method of alkali isomerization using safflower seed oil (SSO). A total of 250 hens (200 days of age) were fed control diet (commercial formula feed for han) or CLA-supplemented diet (1%, 2.5% and 5% CLA) or 5% SSO supplemented diet for 6 weeks, and eggs were collected for analysis of CLA, fatty acid compositons and lipid oxidation. Eggs from CLA-supplemented diets groups showed significantly (p＜0.05) higher CLA content compared to those of control group. The contents of linoleic, palmitic, and myristic acid were increased as well as CLA content by feeding a CLA-supplemented diet. However, the contents of oleic and arachidonic acids in egg yolks were decreased by dietary CLA supplementation. The pH of egg yolk increased by the levels of CLA during storage. The contents of CLA were not significantly (p＜0.05) changed during chilled storage for 28 days, whereas TBARS were significantly (p＜0.05) increased. It is suggested that lipid oxidation of egg yolk might be affected by the levels of CLA in egg yolk due to changes in fatty acid compositions.

• Korean journal of food and cookery science
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• v.12 no.3
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• pp.295-299
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• 1996

Egg yolk oil was obtained from a roasting and Pressure egg yolks obtained from cage system, open barn system, respectively. Lipids in egg yolk oil were extracted with a mixture of chroform: methanol (2:1, v/v) and fractionated into neutral lipid, glycolipid and phospholipid by silicic aicd column chromatography. Lipid components of each fraction were determined by thin layer chromatography (TLC). The results were sum- marized as follows: lipid content of egg yolk from each cage system (A) and open barn system (B) was 31. 05% and 33.34%, and the lipid is made up of neutral lipid 76.60%, 71.23%, glycolipid 3.95％, 5.03% and phospholipids 19.45%, 23.74% respectively. Triglycerides (A: 59.3%, B: 56.3%) were the major components among the neutral lipids; monoglycerides, diglycerides, free sterols, and free fatty acids were the minor cop- monents. The major components of the glycolipids were digalactosyl diglycerides (A: 98.3%, B: 97.8%), the other components were cerebrosides. The major components of the phophoslipids were phosphatidyl choline plus phosphatidyl serine (A: 58.6%, B: 59.8%) the other components were lecithin plus sphingomyelin.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.3
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• pp.417-423
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• 2017

Objective: This experiment investigated the effects of dietary supplementation with conjugated linoleic acid (CLA) on the serum components, laying hen productivity, lipid composition of egg yolk, egg flavor and egg quality. Methods: Healthy 28-week-old Hy-Line white laying hens (n = 480) were divided randomly into 4 groups, 6 replicates/group, 20 birds/replicate. The 30-day experimental diets included 0% (control), 0.4%, 0.8%, and 1.6% CLA. Some serum indices of the birds, and egg production, quality, fatty acid composition, egg quality were measured. Results: The dietary supplementation with 0.4%, 0.8%, and 1.6% CLA did not significantly affect the laying rate and feed intake, as well as calcium ion and phosphorus ion concentration in serum (p>0.05). However, the CLA had significantly increased the strength of eggshell, decreased the odor, flavor, and taste of egg yolk, deepened the color of egg yolk, increased saturated fatty acids and polyunsaturated fatty acids, and reduced the monounsaturated fatty acids (p<0.05). On the other hand, the dietary supplementation with 1.6% CLA had significant effects on feed/gain, and improved serum hormones. Dietary supplementation with 0.4% and 0.8% CLA can significantly enhance the activity of alkaline phosphates. Conclusion: CLA has no effect on production performance, but does enhance the lipid content of the egg yolk and the strength of the eggshell.

• Korean Journal of Poultry Science
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• v.21 no.3
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• pp.183-193
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• 1994

White Leghorn hens were fed a commercial formula feeds as a basal diet, which was supplemented with 3 types of plant oil safflower, evening primrose and pine seed, at the 10% level for 3 weeks. No significant changes was found between the basal diet and the oil feeding trials in the egg yolk cholesterol content, the laying rate, the egg weight, and the yolk weight, except the feed intake. In the fatty acid composition of the egg yolk lipid, however, the plant oil feedings to hens resulted in considerable increase of $C_{18:2}$ acid with a simultaneous decrease of $C_{18:2}$ acid ,and, consequently, followed by the improvement of balance with P /S and P /M /S ratio close to 1.0 and 1:1:1, which is known a desirable ratio for human health in lipid nutrition, respectively.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.3
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• pp.391-397
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• 2015

Two hundred and sixteen Institut de S$\acute{e}$lection Animale (ISA) brown layers (40 wks of age) were studied for 6 wks to examine the effect of microalgae powder (MAP) on egg production, egg quality, blood lipid profile, and fatty acid concentration of egg yolk. Dietary treatments were as follows: i) CON (basal diet), ii) 0.5% MAP (CON+0.5% Schizochytrium powder), and iii) 1.0% MAP (CON+1.0% Schizochytrium powder). From 44 to 46 wks, egg production was higher in 1.0% MAP treatment than in control treatment (linear, p = 0.034); however, there was no difference on the egg production from 40 to 43 wks (p>0.05). Serum triglyceride and total cholesterol were significantly reduced in the groups fed with MAP, compared to those in groups fed with control diets (Quadratic, p = 0.034 and p = 0.039, respectively). Inclusion of 0.5% MAP in the diet of layers improved egg yolk color, compared with hens fed with basal diet at 46 wks (quadratic, p = 0.044). Eggshell thickness was linearly increased in MAP-fed treatments at 46th wk (p<0.05). Concentration of yolk docosahexaenoic acid (DHA; C22:6n-3) was increased in treatment groups fed with MAP (linear, p<0.05). The n-6 fatty acids, n-6/n-3 fatty acid, and unsaturated fatty acid/saturated fatty acid were decreased in treatment groups fed with MAP (linear, p<0.05). These results suggest that MAP improved the egg production and egg quality, and may affect serum lipid metabolites in the layers. In addition, MAP increases yolk DHA levels, and deceases n-6/n-3 fatty acid ratio.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.2
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• pp.234-239
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• 2010

Effects of polyunsaturated fatty acid (PUFA) and vitamin E (VE) supplementation in the diet of breeder hens on the egg quality and hatchability, lipid peroxides of the egg yolk, and development of the newly-hatched offspring chicks were investigated. A total of 800 Avian 48, 28 wk-old broiler breeders were assigned randomly to 4 groups with 4 replicates of 45 females and 5 males. Each group was fed one of the following four diets with different oil sources and levels of VE: corn oil (CO), fish oil (FO), CO+VE and FO+VE. The results showed that: i) Addition of FO in the breeder diet reduced the whole egg weight, yolk weight, albumen weight, yolk color score and neonatal offspring chick body weight without affecting the hatchability as compared to the CO treatment. ii) Addition of VE efficiently reduced the lipid peroxides of egg yolk from hens fed diets containing FO. iii) VE in the breeder diet significantly promoted the development of liver and heart of the chick offspring.