Lipids are a diverse group of fatty substances found in all living organisms. Lipids do not dissolve in water but are soluble in alcohol, ether, or other organic solvents because all lipids are hydrophobic. They have lower densities than water, and may have consistencies at ambient temperature of solid, semisolid, or clear liquid.
The smoke point of various fats is important to note because a fat is no longer good for consumption after it has exceeded its smoke point and has begun to break down. Once a fat starts to smoke, it usually will emit a harsh smell and fill the air with smoke. In addition it is believed that fats that have gone past their smoke points contain a large quantity of free radicals which contribute to risk of cancer.
Fats composed mainly of saturated fatty acids are solid at room temperature, and the greater the saturated fat content, the higher will be the temperature of melting. Animal fats are highly saturated such as coconut oil. At the opposite end of this chemical spectrum are the polyunsaturated vegetable oils, all of which stay liquid at colder temperatures. The lower the temperature, at which solidification occurs, the greater the degree of unsaturation. Corn and soybean oil are examples of polyunsaturated fats. In the middle of the spectrum are the vegetable oils composed primarily of monounsaturated fatty acids, those with just one double or triple bond in the chain of carbon atoms such as olive oil.
The higher the number of carbon chains attached, the higher the solidification point. And the higher the degree of unsaturation the fat has, the lower the solidification point.
Creaming or sedimentation can result from the action of gravitational force on phases that differ in density.
One of the most common uses of fats is in emulsions such as mayonnaise, and margarines. In emulsions, fat and a liquid such as water or vinegar are suspended in each other. Some emulsions use emulsifying agents, such as lecithin or monoglcyerides, to help keep the fat and liquid from separating. Other emulsions may be stable without the use of emulsifying agents. One of the factors which helps determine the emulsifying capacity of a fat is its water holding capacity, or the amount of water which can be taken up by a fat before the fat and water begin to separate.
Fat bloom is the visible accumulation of large cocoa butter crystals on the chocolate surface. It is often accompanied by numerous mini cracks that also give a dull appearance.