Eggs

• Structure of an egg

  The eggshell

  Shell membranes

  Air cell

  The egg yolk

  The chalazae

  The egg white/Albumen
• The eggshell

  This protects the egg. It has small holes which let water pass out of the shell and allows air to enter over time.
• Shell membranes


  These are on the inside of the shell and slow down the loss of water evaporating from the egg. They also help to prevent the entry of bacteria.
• Air cell


  This becomes larger as the egg becomes older, because the water from the egg evaporates through the shell.
• The egg yolk


  This is the yellow oily part at the centre of the egg. This feeds the developing chick if the egg was fertilised
• The chalazae


  These are the twisted protein strands at either end of the egg yolk which hold it in place in the centre of the egg
• The egg white/Albumen


  This surrounds the yolk. As the egg gets older it becomes thinner and more watery.
• Nutritional Value of an Egg

  Yolk:

  Water - 50%

  Protein - 16.5%

  Vitamins - A,D,E,K

  Fat - 33% omega 3

  Minerals - iron (only absorbed if eaten with vitamin C)

  Energy - Average egg between 55 & 80 calories

  White:

  Water - 88.5%

  Protein - 10.5% Ovalbumin, Mucin

  Vitamins - Riboflavin

  Fat - Trace
• Eggs we eat in GB come from the following birds:

  Hens, geese, ducks, quale.
• There are 4 different farming methods

  0 - Organic

  1 - Free range

  2 - Barn

  3 - Cage/Battery
• Organic

  Advantages

  • Organic
  • They have freedom

  Disadvantages

  • Hard to control
  • Expensive
• Free Range

  Advantages

  • They get fresh air

  Disadvantages

  • Might lose them
• Barn

  Advantages

  • Hens move freely inside the barn

  Disadvantages

  • Requires huge spaces
  • Noisy
• Cage/Battery

  Advantages

  • Cheap
  • Few workers/spaces needed

  Disadvantages

  • Less moving areas
  • Live shorter
• There are 3 different classes of eggs

  Highest

  Class A: Naturally clean, fresh eggs, internally perfect, yolk stays in middle

  Class B: Broken out and pasteurised

  Class C: Industrial eggs

  Lowest
• Egg sizes

  V. large = 73g+

  Large = 63-73g

  Medium = 53-63g

  Small = <53g
• The British Lion mark is part of a quality assurance scheme. It means the eggs are:

  1. Vaccinated against salmonella
  2. Produced to a strict code of practice
  3. British eggs from hens
• What information appears on an egg box?

  Country of origin, certification mark, lion mark, best before, display until date, name of supermarket, size of eggs, amount of eggs, farm ID
• Aeration


  Egg proteins can stretch as it is whisked or beaten due to the ability of ovalbumin to stretch. Air becomes trapped within the eggs and this makes the mixture light and foamy. It can also act as a raising agent during cake making.

  Examples: Mousses, cold souffles, sponges, meringues
• Binding


  Eggs coagulate (become solid) when heated.

  Examples: Fish cakes, burgers, stuffing, meatloaf
• Coating


  Before frying, foods are coated in raw eggs then dipped into crumbs or flour. The egg protein coagulates on heating, sealing the food, forming a crispy coating and preventing the food from overcooking.

  Examples: Scotch eggs, fish cakes, rissoles, fish is batter
• Emulsification


  Egg yolk contains lecithin, which holds together oil and water and stops from separating.

  Examples: Mayonnaise, aioli, butter, creaming mixture for cakes
• Enriching


  Adding egg to a dish makes it richer in nutrients.

  Examples: Sauces, custards, mashed potato, milk puddings
• Glazing


  Beaten egg, egg yolk or egg white is brushed over the surface of the food to give a shine and golden brown colour.

  Examples: Savoury pastry dishes, bread, scones, pie
• Garnishing


  Sliced boiled egg is used to add colour to a dish.

  Examples: Salads, sandwich, toasts, breakfast plates
• Thickening


  Egg protein coagulates on heating and causes thickening

  Examples: Sauce, custards, soups, mayonnaise
• Prices

  Battery: £1.99 for 15 eggs (13p each)

  Barn: £1.4 for 10 eggs (14p each)

  Free Range: £3 for 10 eggs (30p each)

  Organic: £2.5 for 6 eggs (42p each)

  Barn and battery are cheaper because it's also cheaper to farm in those ways. Free range is more expensive because it's more expensive to farm and have a higher quality. Same for organic which is the most expensive one.

  Factors that influence our choice when shopping for eggs: Country of origin, prices.