Syneresis can occur when the egg is overcooked. This is when the texture becomes porous as the protein shrinks and pockets of water are left in the product. Between 60-65C is the temperature which egg whites start to coagulate and the result of this the egg white changes appearance from transparent like to white and the texture will be from gel like to solid texture. Egg yolk starts to coagulate at a higher temperature than egg white, it begins coagulating at 65C and finish at 70C. From the darker yellow appearance of the egg yolk it will turn into a lighter yellow yolk and from runny yolk it can go to powdery solid yolk.
There are a number of factors that will affect coagulation. A firmer set can be achieved at a lower temperature if an acid such as lemon juice is added. A looser set and higher coagulation temperature is achieved by the addition of sugar to the mixture. The quantity of egg yolk determines the strength of the set mixture. A higher proportion of egg yolks or whole eggs will produce firmer or thicker custard. A low heat achieves gentle heat transference, which produce perfect conditions for a coagulation.
Aeration is when egg white is whisked. Foam is formed when air is dispersed through the liquid egg white. Egg whites can be aerated due to the ability of the ovalbu, in to stretch and hold air. When egg whites is whisked the proteins are denatures and uncoil. This forms a 3D air / liquid structure that can hold air when folded into food mixtures. The foam is stable but its properties can be affected by the use of additional ingredients or conditions.
First factor that can affect foam formation is salt. It decreases the pH of the egg white and this increases the resistance to foam, so the time taken to foam is increased. It gives the foam more stable and it enhances the flavour.
Second factor is sugar. Sugar interferes with the bonds that form as the egg whites uncoil. Therefore the whisking time is increased and the resulting foam is denser, however the foam is more stable. This factor is commonly used for meringues.
Fat affects foam formation. Fat such as egg yolk prevents new bonds being formed in the structure.
Fourthly alkalis will increase the pH of the foam, decreasing the foaming time but making the foam stable.
Lastly will be acids. Acids such as tartaric and acetic will soften the foam.
Because the fat in the egg yolk, it inhibits the aeration recipes are usually for egg whites. However sponge cakes do use whole eggs. They are whisked with sugar over a pan of hot water (double boiler method) it works because the whisking action causes the proteins to denature and the heat causes coagulate resulting in stable form.
Emulsion is formed when one liquid is dispersed in the small droplets into a second liquid with which it will not normally mix. Egg yolk has emulsification properties, which means it has the ability to hold large quantities of fat in an emulsion. Lecithin is present in egg yolk, which has a hydrophobic (water hating) component and hydrophilic (water loving) component.
Eggs have many other functions. An egg can give additional thickness to sauces; it can also be use as binding and coating agent. Eggs can also be used as an egg washed or sometimes called glazing and commonly used for the top of pastries and breads. It also add colour and enrichment.
by
iamcamille23 (student)
