Frequently Asked Questions
Why is coffee oily ?
Arabica and Robusta coffee contain different levels of lipids, 0.2 to 0.3% present in a waxy layer surrounding and protecting the bean. The total lipid content of Arabica is around 15%, but levels up to 17% have been measured. In Robusta the average is, according to different authors, 10 or 15%, but can be as low as 7%. The lipids in green coffee are as follows:
| Constituent | % Total lipids |
| Triglycerides | 70-80 |
| Free fatty acids | 0.5 - 2.7 |
| Diterpene esters | 15 - 18.5 |
| Free diterpenes | 0.1 - 1.2 |
| Triterpenes, sterols, and sterol esters | 1.4 - 3.2 |
| 5-Hydroxytryptamides and derivatives | 0.3 - 0.7 |
| Tocopherols | 0.3 - 0.7 |
| Phosphatides | 0.3 |
It is noted that the fatty acid composition differs between the outer wax and the bean oil fraction.
