HOW ARE EGG PRODUCTS PRODUCED?

Most egg products are available in liquid, frozen or spray dried form. Shell eggs are broken on automated machines at speeds ranging from 21,000 - 65,000 eggs per hour. The quality of the internal contents of the eggs are carefully monitored at this stage, including visual checking, to ensure that there are no impurities. The eggs are either separated into whites and yolks or remain as liquid whole egg. The egg is then pumped through filters which extract any shell particles and remaining chalaza (inner thick layer) and then cooled to less than 4°C. This cooling stage is important as it inhibits bacterial growth.

Liquid egg products
Many liquid egg products are now blended with other ingredients to produce a more useful ingredient, especially for the baking industry. Prior to pasteurising, blending takes place using other ingredients such as sugar and salt, this not only prolongs the life of the liquid egg, but also eliminates a procedure for the customer. The egg is then pasteurised using either plate heat exchangers or tubular pasteurisers (see below). Common products with ingredients added are salted yolk, which is used in mayonnaise, and sugared white, which is used to make meringues.

Liquid egg is normally supplied in 1,000 kilo bag-in-box format. The product can be hygienically filled into such containers and customers would normally pump the product from the boxes to the mixing points. The standard shelf life of this product is given as four days at 0-4°c.

Pasteurisation
Tube pasteurisation is becoming more popular as it allows longer operating periods and higher temperatures. Current legislation requires liquid whole egg to be pasteurised at 64.4°C for a minimum of 2.5 minutes. This time/temperature relationship effectively destroys all pathogens and reduces total bacterial counts to a low level. After pasteurisation the egg is cooled to below 4°C to await packing or spray drying.

Dried egg products
Whole egg and yolk are spray dried in tower or box spray driers. The product is atomised into a hot air stream and instantly dried. The powder is then removed from the drier via cyclones or bag filters.

The conversion of liquid egg albumen (egg white) is a different process. Firstly albumen is not pasteurised prior to drying because the egg proteins are extremely sensitive to heat in liquid albumen. Before drying the albumen has to be de-sugared to remove the glucose present. This step is necessary to prevent the 'Maillard' reaction between the egg proteins and the glucose in the powder on storage. De-sugaring is normally effected using a bacterial fermentation after which the product is spray dried.

Once dried, the albumen powder has to be pasteurised and this is done in hot rooms over a period of about 14 days. The product is checked and is only released from the hot room when bacterial loadings are acceptable. Egg powders nowadays are highly functional, easy to use and can be positively released.

Frozen egg products
Frozen egg is used primarily by smaller manufacturers. However sales of frozen products are declining, as the number of smaller manufacturers is diminishing, and the larger organisation find alternative products more appropriate to their needs.