Candling Opening the egg by breaking it is the only accurate way to fully check the interior quality. This can only be done on a limited sample basis. “Candling” can show some aspects of internal quality without breaking the shell.
It consists of inspecting the egg in a beam of light strong enough to penetrate the shell and illuminate the contents. Various types of lamps can be used but the essential features are similar.
An incandescent-type bulb of 25 to 50 watts is enclosed in a casing with light exiting through a round hole about 3 cm in diameter against which the egg is held and turned.
The casing usually has another hole to provide light for the operator to see the egg container if the room is very dark. By rotating the hand-held egg close to the hole in the candler, the yolk and egg white quality can be estimated by their movement.
Experienced operators can candle 24 eggs per minute. The main points to observe are summarised in the following paragraphs.
Egg white (albumin) characteristics showing good egg quality are thick albumin fullness and albumin transparency.
When the thick albumin sack is strong and healthy, it is full and confines the yolk within the various layers of egg white.
As the thick albumin sack deteriorates, its contents leak into the thin albumin cavity. The yolk then moves more freely, increasing the risk that it might touch the shell and be contaminated by micro-organisms from outside the shell.
A healthy albumin is also transparent. It can become discoloured or cloudy due to rot or overexposure to hot water (partial coagulation) in washing.
Yolk characteristics showing good egg quality are confinement within the thick albumin, a small spherical shape, orange-yellow colour and the absence of spots.
As described in the above paragraph, yolk confinement within the albumin protects the yolk from outside contaminants. A small spherical shape indicates a strong yolk membrane.
When the egg is exposed to high temperatures and dehydration, the yolk deteriorates and grows larger and flatter. Consumers prefer yolks of orange-yellow colour without spots.
Spots on the yolk can indicate:
x embryo development (reddish colour);
x blood from the hen’s ovary and “meat” bits from the oviduct released during egg formation (red and brown, respectively);
x moulds (grey or black); or
x bacterial rots (blue, violet, green or red).
Although consumers prefer yolks with no spots, the only spots that pose any health risk are mould and rot spots.
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Air cell characteristics showing good egg quality are small size, shallow depth and fixed position at the blunt end of the egg.
Small size and shallow depth indicate very little loss of moisture from the egg contents, which in turn indicates freshness (or that the eggs have been stored under good conditions).
A fixed position at the blunt end of the egg indicates that the membranes surrounding the air cell have not been damaged (for example, by rough handling).
There is usually a correlation between the depth of the air cell and other quality aspects. However an egg stored at high temperature and high humidity may show a good air cell depth (as the high humidity maintains the egg moisture) but it may have deteriorated otherwise (as a result of the high temperature).
Air cells can be deflated completely or become unfixed and mobile within the egg. The air cell can become filled with albumin if part of the inner shell membrane is broken.
If the membrane is merely weakened, the air cell may move freely around the egg. These mobile air cells are often caused by transporting eggs on rough roads or by the egg being stored small end upwards. The egg could be otherwise quite fresh.
Before candling, eggshell quality is assessed, and eggs that are dirty, cracked, thin, rough or misshapen are processed accordingly .
With the above in mind I wish you all the best in your sales and more income opportunities in your farming ventures.
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