If you’re fond of eggs and you use eggs in your meals frequently, then this article is just for you. Here are some facts about the size, colour, yolk and other eggy stuff.

Keeping eggs fresh: Keep eggs in the fridge until you need them.  The date stamp on your carton will tell you how long they will stay fresh for.  Eggs lose their quality very quickly at room temperature, so refrigerate them immediately after purchase.

Clean egg shells: Look for shells that are clean and whole.

Size: Have you ever found an egg in your carton which is smaller than the rest?  Egg sizing is done by the egg’s weight, rather than its circumference.  Many things contribute to the weight (or density) of an egg, for example the age of the hen (younger hens lay heavier, smaller eggs) and the amount of water in the egg (in summer hens drink more water which makes the eggs lighter).

Bloom: Egg shells are covered with a natural coating that seals its pores. This helps to prevent bacteria from getting inside the shell and reduces moisture loss. Wiping or washing eggs removes the protective coating and reduces the lifetime of the egg.

Candling: When eggs are being graded they roll over a bright light which makes the egg transparent so the grader can check the inside of the egg for quality. Long ago, candling was done by holding the egg up before a lit candle, which is how this part of the grading process got its name. Today eggs pass over high-intensity lights on rollers so all of the egg can be viewed.

Chalaza: The yolk is anchored to the white by tiny strands of egg white called chalaza. The more prominent the chalazae, the fresher the egg.

Colour: Egg shell and yolk colour will vary depending on the diet of the hen.  Colour variations have no effect on the quality, flavour, or nutritional value of the egg. The breed of hen determines the colour of the shell.

The yolk: The yolk or yellow portion makes up about 33% of the liquid weight of the egg. It contains all of the fat in the egg and a little less than half of the protein. The yolk contains all this goodness because in fertilised eggs the yolk is the site of embryo formation.

With the exception of riboflavin and niacin, the yolk contains a higher proportion of the egg's vitamins than the white. All of the egg's vitamins A, D and E are in the yolk. Egg yolks are one of the few foods naturally containing vitamin D (the sunshine vitamin). The yolk also contains more phosphorus, manganese, iron, iodine, copper, and calcium than the white, and it contains all of the zinc. The yolk of a Large egg contains about 59 calories. It is the yolk which is responsible for the egg's emulsifying properties in cooking.

Double-yolkers: Double-yolkers are created when a hen releases two yolks at the same time.  This is quite common in young hens whose cycles may not be perfectly synchronized.

Freshness: The best before date on a carton of eggs tells you how long the eggs inside it stay ‘fresh’ if they are kept refrigerated after purchase. During this time (usually about 35 days) there is little change in the nutritional value of the egg, but the appearance and qualities of the egg may change as the egg ages. Poached or fried eggs hold their shape better the fresher the egg, but hard boiled eggs are much easier to peel if the eggs are at least one week old.

Temperature, humidity and handling all contribute to freshness. A one week old egg kept in ideal conditions can be fresher than an egg left at room temperature for one day.