One of the myths that most people dieting has is that “you should always consume egg whites” though this is part right because the whites are, as I wrote before, an excellent source of proteins, however the yolks have an excellent nutritional value.
The yolk is the centra and orange part of the egg. It’s surrounded by the Vitellius ,which gives the yolk shape and allow it to keep separated from the white. In the yolk there’s the main vitamins, lipids and minerals from egg, what makes them really valuable.
Occasionally you may find two yolk eggs. This is because the hen produces on the same ovulation 2 eggs instead of just one, which is the regular deal. This physiologic accident is mostly comun on birds at their first posture period.
As a food. The yolks are the biggest source of vitamins and minerals on the egg, it contents also all the fat and cholesterol, approximately 50% of the yolk is water, and the solids are equally splinted into proteins and lipids, and a small fraction for vitamins! minerals and carotenoids, this is an antioxidant and the responsable for the color in the yolk.
The yolk color has a comercial interest, and it can be measured with color meters, however, it can be influenced by the colorant used on the food, so using the color to determine the nutritional facts of the egg is not quite right nowadays, the yolk can go from almos white, passing thru yellow, orange, red and even olive green, depending on the pigments used on the animal feed, for example if you feed them with large quantities of pepper capsaicin, the color of the yolks will turn reddish or dark orange, and that has nothing to do with coloring during the cooking process.
The red or brown spots that sometimes may be found inside of the eggs shouldn’t be confused with embryo development, those are just epithelial cells from the oviduct that felt when forming the egg, and don’t present any problem for consumption. Can easily be removed with the tip of a clean knife.
One of the most important nutrients that you may find on the egg yolk is the choline. The choline was found to be the necessary nutrient in preventing fatty liver. In 1975, scientists discovered that the administration of choline increased the synthesis and release of acetylcholine by neurons. These discoveries lead to the increased interest in dietary choline and brain function. Today it’s well known that choline it’s important for the correct function of the cells. Humans need choline on their everyday diet to be able to have a normal living, because it’s indispensable to synthesize essential components of membranes and it’s an important source of methyls.
A recent study (November 2010h proved that when the diet lacks choline, almos 80% of the post menopausic women (the subject of this study) had liver and muscle damage. The study also discovered that young women can consume more choline because during pregnancy the female body has higher demands. Choline it’s used to keep the fetus nervous system.