· Inthe 1970s the American heart association recommended that people limit theirdaily cholesterol consumption and egg intake to reduce the risk of CHD.· Eggis cholesterol enriched and contributes to the risk of CHD.· Cholesterolmetabolism is complicated in the human system and the human diet is not thesole factor that decides the level of cholesterol in the blood. · Healthydaily cholesterol intake of less than 300 mg/ day.
· Cholesterolcontent in a typical large egg is 213 mg of cholesterol per yolk; in this way,the daily consumption of one yolk should technically meet the AHA guideline.· If the egg yolk cholesterol content could bereduced to 50% the consumption of two eggs per day will meet the AHA. GENETIC SELECTION:· From agenetic point of view egg cholesterol content is affected by several factorssuch as species of bird breed, or strain and age of fowl.· In the1970s several genetic selection studies aiming to decreases egg yolkcholesterol were carried out.
· Reductionin cholesterol by genetic selection is fairly small (9 to 10mg) and is notsignificant if an average daily intake of cholesterol is about 250 mg.· However,there is a lower limit to egg yolk cholesterol, due to its role in developingthe embryo. · Disadvantageis that genetic selection for low cholesterol eggs results in smaller yolks andsmaller egg size. · Howeverlimited changes in yolk cholesterol concentration (5to 7% reduction) can be achievedby genetic selection.
EFFECTS ONCHOLESTEROL OF DIETARY CHANGE:Effect of fat: · Dietarycholesterol supplementation can increase the concentration of cholesterol ineggs. · Dietaryomega-3 fatty acids are another factor affecting yolk cholesterol content.· Feeding ofbirds with menhaden fish oil and flaxseed results in yolk cholesterolreduction. · Flaxseed Effect of natural products: · Somenatural products have been shown to have the ability to reduce cholesterollevel in humans and animals. · Garlic hasbeen reported to be the most effective agents in reducing the cholesterol levelin yolk and plasma.
· Egg yolkcholesterol was significantly decreased by feeding alfalfa meal, oats,sunflower meal; rice mill feed r wood shaving to laying hens when compares toyolk cholesterol of hens fed the basal diet.· Greatestreduction in egg yolk cholesterol was found by feeding either oats or woodshavings.oats Wood shavings Effect of Phyto sterols:· Phyto sterols (also called plant sterols), which arestructurally and functionally similar to cholesterol in vertebrate animals.· Feeding plant sterols decreases cholesterolconcentration in plasma and egg.Effects of minerals and vitamins: · Dietary microminerals (copper, zinc, vanadium, chromium, and iodine) and minerals or dietaryvitamins (vitamin A, ascorbic acid, and niacin) change the yolk cholesterollevel. · However,the role of vitamins and minerals has not been proved yet beyond doubt. Effects of fibre:· Dietaryfibre is a group of ingredients portion of plant of foods that can be resistantto the human or animal gastrointestinal system, absorbing water and easingdefecation.
· It isthought that fibres could affect cholesterol metabolism through bile acidbinding and stimulate faecal sterol excretion. · Regardlessof the dietary source, feeding fibre to laying hens dilutes the availableenergy content of a diet and, as a result, may limit energy intake andpotentially reduce hepatic cholesterol production especially if prior energyintake had been excessive.PHARMACOLOGICALMETHOD:· Certaindrugs have been successful in lowering egg cholesterol by as much as 50%.
· Drugs lowercholesterol in the egg by either inhibiting the synthesis of cholesterol in thehen or by inhibiting the transfer of cholesterol from the blood to thedeveloping yolk on the ovary. · Today, thedrugs which have shown promise in lowering cholesterol are not yet approved bythe FDA for commercial use. · Chromiumsupplementation to laying hen diets at concentrations of less than 1 ppm havebeen shown to lower egg cholesterol and also improve egg interior quality.· Supplementinga layer ration with chromium picolinate alters lipid profiles in the serum andthe lower cholesterol content f the yolk.
· Even thoughgenetic selection alternative nutrition and pharmaceutical techniques are aneffective strategy in modifying egg cholesterol content, there is a certainlimit possible for the reduction of cholesterol levels.· Liver andthe ovary are the primary sites of cholesterol biosynthesis in the laying bird.(Popjak and tietz,1953;husbands and brown, 1965;weiss et al.
, 1967a).· Most of thecholesterol found in the yolk is synthesized in the liver of the hen,transported by the blood in the form of lipoprotein, and deposited indeveloping follicles; the concentration of plasma cholesterol is not closelyassociated with the concentration of yolk cholesterol.(weiss et al 1967c; Sutton et al.,1984)· Lovastatin,which is an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase , therate limiting enzyme in the cholesterol biosynthesis pathway(rodwell etal.,1976). A method for preparing a lowcholesterol egg product resembling a Sunnysideup egg product comprising:· providing a mold havingyolk cavity and a white cavity;· supplying to the yolkcavity, a simulated yolk portion having a water to dry ingredient ratio of fromabout 0.
8 to about 1.2, and comprising, based on the weight of dry ingredients,from about 20% to about 45% of dry egg white, from about 5% to about 35% of anoil having a P/S of greater than about 0.6, from about 10% to about 15% of adry milk protein source, from about 0.5% to about 7% of vegetable gum, and flavouring,colouring and emulsifiers in an amount sufficient to maintain uniformity in theyolk portion;· Supplying to the whitecavity on top of the yolk portion, a white portion consisting essentially ofliquid egg white;· Freezing the yolk andwhite portions;· Removing the frozen eggproduct from the mold; and· Frying the egg productover low heat to obtain a cooked, natural appearing Sunnyside up egg product. REFERENCE:Ø Modifyingegg yolk cholesterol in the domestic fowl – a review P.STEWART HARGIS.
Ø Low-cholesterol egg product andprocess US 3941892 AØ Reduction of the cholesterolcontent of eggs by the oral administration of lovastatin to laying hens ;Robert G.elkin and John C. Rogler