CHAPTER 20: Lipids

From all the known coffee species, Coffea arabica L. and Coffea canephora Pierre are the only ones which have a commercial value on the coffee trade market. The processing methods and the storage conditions influence the chemical composition and, thereby, the quality of the coffee brew. In this study, the constituents of the lipid fraction will be presented in detail. The lipid content of green arabica coffee beans averages some 15% whilst robusta coffees contain much less, namely around 10%. Coffee oil is composed mainly of triacylglycerides. In contrast to the known vegetable oils, the relatively large unsaponifiable fraction is rich in diterpenes of the kaurane family, mainly cafestol, kahweol, and 16-O-methylcafestol, which have aroused a great deal of interest in recent years due to their different physiological effects. Furthermore, 16-O-methylcafestol serves as a reliable indicator for robusta coffee in coffee blends. In addition, a number of 5-hydroxytryptamides have been identified in the waxy layer covering the coffee bean. The influence of the manufacturing processes (storage, roasting, water treatment, and decaffeination) in regard to lipid constituents as well as their impact on the cup quality of the brew have been described in this study.