December 16, 2018

1.1 So we think we know about eggs ?

This material serves as a useful introduction for (new) employees.

First take a look a these two videos explaining the table egg industry and the chain of production. Total length 10min.



Some interesting facts

  • Eggs are the highest quality, most cost effective source of animal protein, essential in feeding a growing worldwide population.
  • For a hen, it takes about 25 hours to make an egg.
  • An average-sized egg weighs approximately 57 grams or 2 ounces. Of this total weight, the shell constitutes 11 percent; the white, 58 percent; and the yolk, 31 percent. Normally, these proportions do not vary appreciably for either small or large eggs.
  • An average-sized egg weighs approximately 57 grams or 2 ounces. Of this total weight, the shell constitutes 11 percent; the white, 58 percent; and the yolk, 31 percent. Normally, these proportions do not vary appreciably for either small or large eggs.
  • An egg contains all the nutrients the human body needs except vitamin C. Most of the nutrients, especially fats and vitamins, are in the yolk.  An egg is particularly rich of fat and biological egg white.  The egg contains in larger quantities the vitamins  E, B1, B2, B6, A and the minerals phosphorus, calcium, potassium, sodium and iron
  • Each hen lays about five eggs a week. The first lay begins when the hen is about four and a half months old.
  • How many Calories in an egg?  An average egg 61 grams (55 grams without scale) provides 75 calories (315 kJ)
  • Eggs are regularly used for purposes other than food, as in paints, varnishes, ink, soap, shampoos, animal feeds, fertilizers, and vaccines. The foaming ability and heat coagulability of the proteins in egg white have made this product invaluable to the confectionary  and bakery trades.
  • The egg is one of the few foods fresh, untreated, may be stored for 28 days ready for consumption
  • The egg is perfectly integrated in the Mediterranean diet and food culture in both snacks, starters and main courses, desserts, and different meals.

Components of an egg – the science bit

  • Air Cell or Air Chamber: At the large end of the egg, it is the empty space between the white and shell.  As a newly laid egg, there is no air chamber. The content of the egg can shrink by cooling and an air chamber may occur. If an egg is kept for a long time, the air chamber will increase. This is because the water will evaporate from the egg.
  • Chalazae: Cord-like strands of egg white that indicate egg’s freshness.
  • Germinal Disc: This is the ovary of the egg if the egg is fertilized.  It looks like a slight depression on the surface of the yolk but is actually the channel leading to the centre of the yolk. When an egg is fertilized this disc allows sperm to enter and travel to the centre allowing the embryo to form.
  • Shell & Egg Skin: It is the outer covering of an egg that accounts for more than 10% of its total weight. It is largely composed of calcium carbonate with small amounts of calcium phosphate, organic matter (including protein) and magnesium carbonate. Its colour may range from white to brown and inside of an egg’s shell are two membranes (inner and outer).  The shell consists largely of lime and is porous colour of the shell. It  does not affect the taste. De schaal bestaat grotendeels uit kalk en is poreus. The outer membrane is also called the egg skin (cuticle). This layer prevents the egg drying out and ensures that micro-organisms can’t penetrate.  The layer has a soft sheen. When the egg is laid, the cuticle is a mucous membrane, after a few minutes it is dry.
  • Membranes : An egg’s interior has two membranes.  The function of the membrane is to ward off the bacteria, they keep the protein together and maintain the air chamber.
  • Albumen:It is known as the egg white and contains more than half of the egg’s total protein, niacin, chlorine, riboflavin, magnesium, sodium, potassium and sulphur.  The white contains of certain amount of ‘thick white’ and ‘thin white’.
    • Thick Albumen: The thick albumen is the third layer from the shell (egg white) and provides the major source of riboflavin and protein. It stands higher and spreads less than the thin albumen but is less prominent in lower grade eggs.
    • Thin Albumen: The thin albumen is the second layer from the shell (egg white) and spreads around the thick white of the egg
  • Yolk: The yellow portion of the egg that is based on the diet of the hen. It encompasses about 33% of the egg’s liquid weight and contains the major source of vitamins (A, D and E), minerals (phosphorus, manganese, iron, iodine, copper, and calcium, zinc) and about half of the protein. The yolk also contains all of the egg’s fat.
  • Hail Cords: The hail cords keep the yolk in the middle. When an egg gets older, the ‘thick white’ will be converted into ‘thin white’. Therefore, the hail cords lose their grip and the yolk can rise up in the egg. The hail cord that leads to the tapering tip of the egg is the strongest.

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