Egg yolk fat

Hens, like many other vertebrates, are not able to synthesize PUFA, especially linoleic acid, from the non-fats in the feed (such as carbohydrates and proteins). This explains the conspicuously high proportion of saturated and monoenoic FA (snch as Cig, Cig g, Cig. ) in the egg yolk fat after a low-fat diet (Table 14.10A,B). 

Huang et al. (1990) show further connections between dietary and egg yolk fat on closer examination of n-3 FA from menhaden oil. It was demonstrated that the amounts of n-3 FA, EPA, and DHA in egg yolk fat are not proportional to those in the feed, although EPA is metabolized in a high proportion. The quantities of docosapentaenoic acid and DHA in the egg yolk react in inverse proportions to the content in menhaden oil. Differences in the absorption rate of both acids in the intestine are assumed to be responsible. 

The most striking fact is that the proportion of linolenate in the storage fat is decreased by feeding polyunsaturated acids and is increased by the administration of fat-free diets. Thus, Reiser et al. (1951) observed that on normal rations the neutral fat and phospholipid of the egg-yolk fat of hens contained only 0.18% and 0.00%, respectively, of trienoic acids. After 52 weeks on a fat-free diet, the trienoic acid content of the above fractions of egg yolk was found to be 0.42% and 2.3%, respectively. Heart fatty acids, which normally had a content of 22% of trienoic acid, were found to have only about 4% after supplementation with corn oil... 

The animal fats which may contain relatively high amounts of EFA include that from the hog, from the fowl, and especially that in the egg. Thus, on a hempseed oil diet, egg-yolk fat contained as much as 41.9% of linoleate and 10% of linolenate. Likewise, pig fat was reported as having as much as 38.9% of linoleate and 0.5% of linolenate following a soybean oil diet (Deuel, 1954a). However, these high values have not been confirmed by bio-assay. Thomasson (1953) reported a value of only 6.9% for lard when tested by the latter procedure. 

Lecithin. Lecithin [8002-43-5] (qv) is a mixture of fat-like compounds that includes phosphatidyl choline, phosphatidyl ethanolamines, inositol phosphatides, and other compounds (37). Commercial lecithin was originally obtained from egg yolks, but is now extracted from soybean oil. Lecithin is used in many products, including margarine, chocolate, ice cream, cake batter, and bread. 

Additive (dried flower meal or solvent extract) to poultry feed, to enhance the yellow color of flesh and egg yolks minor use of extract as food colorant typical applications salad dressings, ice cream, dairy products, other foods with high fat contents, soft drinks, bakery products, jams and confectionery... 

A typical characteristic of many food products is that these are multi-phase products. The arrangement of the different phases leads to a microstructure that determines the properties of the product. Mayonnaise, for example, is an emulsion of about 80% oil in water, stabilized by egg yolk protein. The size of the oil droplets determines the rheology of the mayonnaise, and hence, the mouthfeel and the consumer liking. Ice cream is a product that consists of four phases. Figure 1 shows this structure schematically. Air bubbles are dispersed in a water matrix containing sugar molecules and ice crystals. The air bubbles are stabilized by partial coalesced fat droplets. The mouthfeel of ice cream is determined by a combination of the air bubble size, the fat droplet size and the ice crystal size. 

Eggnog is a flavored dairy drink with seasonally maximum sales in November and December in the United States. It must contain 6% milk fat and 1% egg yolk, with up to 0.5% stabilizer and about 7% sugar. Flavorings include nutmeg, cinnamon, vanilla, and rum concentrate. 

Product Weight (lb/gal) Total Food Solids (lb/gal) Total Milk Solids (%) Milk Fat <%) Whey Solids (%) Egg Yolk Solids (%)... 

In 1912, Hopkins reported a factor m milk needed for the growth of rats. In 1913, Osborne and Mendel demonstrated that milk factor is fat soluble, and present in other fats also, McCollum and Davis, in 1913-1915, identified milk factor (fat-soluble A) in butter and egg yolk. In 1917, McCollum and Simmonds found xerophthalmia in rats due to lack of fat-soluble A. In 1920, Drummond renamed fat-soluble A, vitamin A. In 1930, Moore determined that carotene is a precursor of vitamin A. See also . During 1930-1937, Karrer et al, isolated and synthesized vitamin A. In 1935, Wald reported visual purple in retina to be a complex of protein and vitamin A. 

Artificial butter is commonly obtained by emulsifying oleomargarine with skim milk, usually with the addition of varying proportion of vegetable oils (sesamd, arachis, cottonseed), animal fats (beef fat, neutral hog s fat), aromatic substances (ethyl butyrate, coumarin), and sometimes also casein, lactose and egg-yolk in some cases it is artificially coloured (annatto, coal-tar colours). 

Most binders are solutions, such as linseed oil, which is composed of a number of fat and fatty acid molecules. Egg yolk is composed of water, fat molecules, lecithin, protein, dextrose, cholesterol, lutein, and other trace substances. These compositions of binding solutions allow more opportunities for uniform pigment adhesion and permanent paint qualities. 

In an aluminum bowl, using a rubber spatula, combine the egg yolks, matzo, foie gras fat, club soda, rosemary, scallions, and salt and pepper to taste. 

The structure of the interfacial layers in food colloids can be quite complex as these are usually comprised of mixtures of a variety of surfactants and all are probably at least partly adsorbed at interfaces which even individually, can form complex adsorption layers. The layers can be viscoelastic. Phospholipids form multi-lamellar structures at the interface and proteins, such as casein, can adsorb in a variety of conformations [78]. Lecithins not only adsorb also at interfaces, but can affect the conformations of adsorbed casein. The situation in food emulsions can be complicated further by the additional presence of solid particles. For example, the fat droplets in homogenized milk are surrounded by a membrane that contains phospholipid, protein and semi-solid casein micelles [78,816], Similarly, the oil droplets in mayonnaise are partly coated with granular particles formed from the phospho and lipo-protein components of egg yolk [78]. Finally, the phospholipids can also interact with proteins and lecithins to form independent vesicles [78], thus creating an additional dispersed phase. 

Many food colloids are stabilized from proteins from milk or eggs [817]. Milk and cream, for example, are stabilized by milk proteins, such as casein micelles, which form a membrane around the oil (fat) droplets [817]. Mayonnaise, hollandaise, and bearnaise, for example, are O/W emulsions mainly stabilized by egg-yolk protein, which is a mixture of lipids (including lecithin), proteins, and lipoproteins [811,817]. The protein-covered oil (fat) droplets are stabilized by a combination of electrostatic and steric stabilization [817]. Alcohols may also be added, such as glycerol, propylene glycol, sorbitol, or sucrose sometimes these are modified by esterification or by... 

Vitamin A A fat-soluble compound found in fish-liver oils, milk, green and yellow vegetables, and egg yolk. It is required for cell growth and development, epithelial tissue growth and protection, and normal vision. 

Cholesterol can be removed from eggs, dairy products and animal fats. Milk and egg yolk can be mixed with (3-cyclodextrin to complex the cholesterol, forming a precipitate that can be removed by centrifugation or filtration. Using cholesterol as a process aid, 80% of the cholesterol has been removed from cheeses84,85 and liquid eggs.86 Similar results have been obtained by treating lard and tallow.79... 

Vitamin A, or retinol, is one of the major fat-soluble vitamins. It is present in many foods the best natural sources are liver, butter, margarine, egg yolk, carrots, spinach, and sweet potatoes. Vitamin A is the precursor of retinal, the essential component of the visual pigment rhodopsin. 

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