Cholesterol in egg

Recently Bourges, Small, and Dervichian (5) reported that a para-crystalline lamellar structure of egg lecithin can solubilize cholesterol up to a maximum of one molecule of cholesterol per molecule of lecithin. However, they conclude that this should not be considered as a molecular association but rather the consequence of the relative arrangement of the molecules in the lamellar structure which is a mutual (solid) solution of lecithin and cholesterol. They also reported that the state of compression in the lamellar structure corresponds to that of a highly compressed mixed monolayer of lecithin-cholesterol. The NMR results of Chapman and Penkett (8) also appear to indicate that solubilization of cholesterol in egg lecithin dispersions results in a highly packed structure in which fatty acyl chains possess little molecular motion. Our results from lecithin-cholesterol monolayers also suggest that these mixed mono-layers are two-dimensional solutions with no specific interaction and that the apparent condensation in some instances is caused by the steric factors of the fatty acyl chains and not by the interaction or association between lecithin and cholesterol. 

The adaptation of methods for lipid extraction and quantification by colorimetric determination of either ester or cholesterol in egg yolk with some contamination of egg white is described. Results are compared with those obtained by a conventional enzymatic determination. 

Pasin, G., Smith, G.M., and O Mahony, M. 1998. Rapid determination of total cholesterol in egg yolk using commercial diagnostic cholesterol reagent. Food Chem. 61 255-259. 

Traditional mayonnaise is an 80% oil-in-water emulsion, which may rely on mustard seeds for solid particle stabilization. Two constituents of egg yolk, lecithin and cholesterol, are surfactants, which promote the formation of oil-in-water and water-in-oil emulsions, respectively. The ratio of lecithin to cholesterol in egg yolk favors the water-in-oil type but the final emulsion type formed is due to the action of mustard seed, which favors an oil-in-water emulsion (Petrowski, 1976). 

Suppose you know that cholesterol in egg noodles can be extracted with ethyl acetate. The D is 0.3 (assumed). How many 50 mL extractions will it take to remove 95% of the cholesterol in a batch of egg noodles (20 mL HjO), if they contain 2.0% cholesterol Assume a 10.0 g sample. 

Nnhitional methods can also be applied to enriching egg yolk lipids with CLA by administering it in adequate doses with feed. However, the effectiveness of nnhitional methods in the reduction of cholesterol in egg yolk lipids is low. The nse of 3-hydroxy-3-methylglutarylo-CoA reductase for this purpose is more effective. In this way, the cholesterol level in egg yolk lipids can be decreased by 30% however, this has consequences in the layers prodnctivity (Pisnlewski et al., 2001 Pszczola et al., 2000). 

The oxidation of cholesterol in egg powder has been detected using H-NMR. P-NMR spectroscopy has been used to quantitate phospholipids in egg lecithin. 

Figure 4.4 NMR spectra quantification of cholesterol in egg yolk lecithin with use of internal standard (I.S.) (a) pure sample (detail) (b) pure sample plus I.S. (c) CH3 signals of the cholesterol reference. Instrument details are given in text. Section 4.10. (Source Spectral Service, unpublished material.)...

Calibration plots of peak area versus nanograms spotted had a linearity correlation coefficient value of 0.98 or greater. Standards were spotted with samples to provide an individual calibration plot for each plate. Scans of duplicate sample aliquots are also shown in Fig. 9. The cholesterol values of 20 egg yolk samples determined by quantitative TLC ranged from 9.7 to 26.2 mg/g (avg 12 mg/g), which is similar to the values reported in the literature for cholesterol in egg yolk from various birds. See Reference 87 a for an update of this study. 

Kansy et al. [550] reported the permeability-lipophilicity relationship for about 120 molecules based on the 10% wt/vol egg lecithin plus 0.5% wt/vol cholesterol in dodecane membrane lipid (model 15.0 in Table 7.3), shown in Fig. 7.23. The vertical axis is proportional to apparent permeability [see Eq. (7.9)]. For log Kd > 1.5, Pa decreases with increasing log Kd. In terms of characteristic permeability-lipophilicity plots of Fig. 7.19, the Kansy result in Fig. 7.23 resembles the bilinear case in Fig. (7.19d). Some of the Pa values may be underestimated for the most lipophilic molecules because membrane retention was not considered in the analysis. 

Without an artificial sink, the membrane retentions are very high, with many basic probe molecules showing R > 80%. With the imposed sink, many of the retentions dropped by as much as 50%. Furthermore, just 0.5% wt/vol cholesterol in dodecane (in addition to the sink) caused increased retention to drop by at least a further 10-30%. It was not possible to form stable cholesterol-containing lipid models under sink conditions with Avanti s egg lecithin acceptor buffer solutions turned significantly turbid in the untenable model 13.1. 

The physiologic sequelae of biotin deficiency are almost unexplored. Severe skin lesions, especially seborrheic dermatitis and Leiner s disease (Erythroderma desquamativum or exfoliative dermatitis), were increased in young infants bom of mothers on a restricted diet low in eggs, livers, and other biotin-rich foods. After biotin administration the lesions healed. There are claims that excess biotin produces a fatty liver characterized by heightened cholesterol content. Choline has no effect in the prevention of biotin-fatty livers (G2, M2). In mice with transplanted tumors, both the tumors and the blood levels of biotin are below normal (R8). More recent studies established a protection with avidin, the biotin-binding fraction of egg white, against tumor formation (K4). More data along these lines are still needed for confirmation. 

In studies on radiation effects on cholesterol in meat [19] and egg powder [20], elevated levels of the same oxides were found that are known to result from autooxidation during storage of unirradiated foods. Vacuum packaging or addition... 

Figure 3. Effect of lipid composition on surface pressure of films of egg lecithin-cholesterol in interaction with rabbit y-globulin at 1 digram/ ml.

Egg Lecithin—Cholesterol Monolayers. The average area per molecule in egg lecithin-cholesterol monolayers shows deviation from the additivity rule at all surface pressures (42). The deviation in this case could be explained by the presence of molecular cavities caused by the kink in the oleoyl chain of egg lecithin, which would reduce the average area per molecule at low as well as high surface pressures (Figure lOg). 

The optimum condensation at molecular ratios of 3 to 1 and 1 to 3 in egg lecithin-cholesterol monolayers and 1 to 1 in dipalmitoyl lecithin-cholesterol monolayers (42) do not imply complex formation between lecithin and cholesterol but rather suggest average geometrical arrangements of these molecules. 

Study looking for good universal method for determination of eight analogs of cholesterol oxides in egg and milk powders. The results indicate difficulty in working with various food samples such as mixed diets. 

Some cholesterol entering from the diet may be esterified to various fatty acids, although the extent of esterification is variable. For example, egg yolk cholesterol is about 10% esterified (Bitman and Wood, 1980 Tattrie, 1972) cholesterol in meat and poultry is at least 50% esterified (Kritchevsky and Tepper, 1961). Esterified cholesterol entering the intestinal tract is mostly hydrolyzed by pancreatic enzymes, yielding free cholesterol and fatty acids (Howies et al., 1996). Only unesterified cholesterol is available for absorption. 

Kern, F., Jr. 1991. Normal plasma cholesterol in an 88-year-old man who eats 25 eggs a day. 

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