A variety of fatty acids
Solid or liquid
A triglyceride is called a fat if it is solid at 25°C; it is called an oil if it is a liquid at that temperature. These differences in melting points reflect not only differences in the degree of unsaturation, but also the number of carbon atoms in the constituent fatty acids. Triglycerides obtained from animal sources are usually solids, while those of plant origin are generally oils. Therefore, we commonly speak of animal fats and vegetable oils.
The fatty acid molecules can deviate from each other in various ways. These differences not only influence the melting behavior, but also play a role in the digestion process. We speak of short fatty acid chains if the fatty acid contains a maximum of 5 carbon atoms. Medium-chain fatty acids contain 6–12 carbons. Long chains are chains with more than 12 carbon atoms. The length of the chain has a major influence on the melting point of a fatty acid. The longer the chain, the higher the melting point.
Butterfat, coconut fat and palm kernel fat contain relatively many short-chain fatty acids. Long-chain fatty acids are mainly found in peanut oil and rapeseed oil.
Fatty acid chains
The properties of fatty acids depend on their chain length, and also on their number of double bonds. So, a short(er) chain length and unsaturation (double bonds) promote the fluidity of fatty acids.
The properties of fatty acids depend on their chain length and degree of saturation.
- Shorter chain fatty acids have lower melting points than longer chain fatty acids.
- Unsaturated fatty acids have a lower melting point than saturated fatty acids with the same chain length.
- The melting points of polyunsaturated fatty acids are even lower.
We use a special code to distinguish the fatty acid molecules. For example, C16:0 is a fatty acid with 16 carbon atoms and 0 double bonds. And C18:3 is a fatty acid with 18 carbon atoms and 3 double bonds. In nature, mainly fatty acid chains with an even number of carbon atoms occur.
We determine the fatty acid composition of a sample in a laboratory using a method called "gas chromatography". The result of a fatty acid composition indicates the percentages for the presence of the different fatty acid molecules in the analyzed sample. A widely used standard for the fatty acid composition is ISO 5509.
Fatty acid table
Below you will find an overview of a number of common fatty acids.