Chemical Aspects Of The Quality Of Kenya Mild Arabica Coffee Kahweol Content of the Green Coffee Beans

Abstract

This thesis records the results or an attempt to substantiate an alleged correlation between relative coffee quality as assessed by the trade liquorers in East Africa and the pre,ence and quantity of the unstable diterpenoid, KAHWEOL, in the green Arabica coffee beans. Methods of isolation of the otherwise 'critical pair' of compounds, KAHWEOL and CAFESTOL, in the diterpene fraction of the unsaponifiable matter from the coffee-bean oil, were studied and a method employing silver nitrate impregnated silica gel G layers was developed for quick separation. Kahweol was estimated from its specific ultra-violet absorption at 289 nm, ensuring quantitative extraction after a reliable oil isolation procedure. No correlation was found to exist between the assessed coffee quality and kahweol content for 20 coffee samples covering a wide range of quality standards and various areas of cultivation in Kenya. Data on oil yield and percentage unsaponifiable matter is included. The results are discussed with a reV1ew of relevant existing literature and the need for a more objective and scientific method of assessing coffee quality.