Grease eye
As fat eyes round accumulations of liquid are more or less fat on the surface of an aqueous liquid such as broth called.
In the past, the number of fat eyes on the soup was considered a sign of prosperity - only the wealthy could afford high-fat food. In the course of the trend towards a low-fat diet , fat eyes are often less desirable today. A low fat content can, however, lead to impaired taste, as many flavors are dissolved in the fat and are lost when it is removed.
Physical
Because of the lower density of fat compared to water, fat droplets always float on the surface. Due to the surface tension of the water and their weight, the drops are pulled apart like a lens, because the surface tension of the water (F3) is greater than the interfacial tension of the fat droplet with the water (F1) and with the air (F2). As long as | F4 | applies to the force F4 = F1 + F2 <| F3 |, as shown in the picture, the fat drop spreads. There will eventually be an equilibrium with | F4 | = | F3 | and reached a certain angle between F1 and F2. In contrast to oil droplets, which spread until they only consist of a single layer of molecules or until the spread e.g. B. is hindered by an edge, grease eyes remain smaller and thicker. Since the surface tension of the water acts the same everywhere on the edge of the fat drop, they remain circular.
When a detergent is added, after it has spread, all of the surface tensions mentioned will generally decrease, ie all corresponding forces will decrease. In particular, a good detergent will reduce the liquid-liquid interfacial tension, then the fat droplets will be pulled apart. With the equilibrium geometry changed in this way, they can be more easily absorbed into the aqueous phase, they are dispersed in it .