A combination of factors:

• shell must be clean, sound, a healthy texture and shape
• the albumen - or egg white - texture and viscosity is important
• colour of the yolk
• there should be no internal foreign matter within the egg

Once collected, the eggs are tested to assess the yolk colour and egg white quality. Egg white quality is measured in Haugh units - an international standard developed by American researcher Dr R Haugh in the 1930s, which measures egg white density.

The higher the Haugh unit reading, the "tighter" the egg white will hold around the yolk and the better the egg quality. (We've all experienced an egg with a low Haugh unit reading. The white is thin and will spread out when fried or poached.)

By objectively measuring eggs, Zeagold Foods can verify the results of its quality systems then adjust any inputs accordingly.