Consumers drink coffee not as nutrition source, but as refreshment drink. For coffee consumers who have high tolerance for caffeine, coffee may warm up and refresh their bodies. High caffeine content in coffee beans may cause several complaints to consumers who are susceptible to caffeine. One of the efforts, for coffee market expansion is product diversification to decaffeinated coffee. Decaffeination process is one of process to reduce caffeine content from agricultural products. Indonesian Coffee and Cocoa Research Institute in collaboration with Bogor Agricultural University has developed a single column reactor for coffee beans decaffeination. The aim of this research is to study process characteristic of coffee decaffeination in single column reactor using ethyl acetate (C4H8O2) solvent. Treatments applicated in the research were time and temperature process. Temperature treatment were 50—60OC, 60—70OC, 70—80OC, 80—90OC and 90—100OC. Time treatment were 2 h, 4 h, 6 h, 8 h, 10 h, and 12 h Size of Robusta coffee beans used were less than 5.5 mm (A4), between 5.5 mm and 6.5 mm (A3), between 6.5 mm and 7.5 mm (A2), and more than 7.5 mm (A1). The result showed that decaffeination process with ethyl acetate solvent will be faster when its temperature was higher and smaller bean size. For bean size less than 5,5 mm, decaffeination process by 10% ethyl acetat can be done 8—10 hours in 90—100OC solvent temperature or 12 hours in 60—70OC solvent temperature for 0.3% caffein content. Organoleptic test showed that 90—100OC temperature solvent treatment decreased coffee flavor, which aroma, bitterness and body values were 1.9 each . Key words : Coffee, caffeine, decaffeination, quality, single column.

A simple mathematic model for caffeine kinetic description during the extraction process (leaching) of coffee bean was developed. A non­steady diffusion equation coupled with a macroscopic mass transfer equation for solvent was developed and them solved analytically. The kinetic of caffeine extraction from coffee bean is depend on initial caffeine content, final caffeine content, caffeine content at certain time, mass­transfer coefficient, solvent volume, surface area of coffee beans, process time, radius of coffee bean, leaching rate of caffeine, caffeine diffusivity and a are constan, solvent concentration, activation energy, temperature absolute and gas constant. Caffeine internal mass diffusivity was estimated by fitting the model to an experiment using acetic acid and liquid waste of cocoa beans fermentation. The prediction equation for leaching rate of caffeine in coffee beans has been found. It was found that Dk (m2/sec)=1.345x10­7—4.1638x10­7, and kL (m/sec)=2.445x10­5—5.551x10­5 by acetic acid as solvent depended on temperature and solvent concentration. The prediction equation for length of time to reduce initial caffeine content to certain concentration in coffee beans has been developed, Caffeine diffusivity (Dk) and mass­transfer coefficient (kL) was found respectively 1.591x 10­7—2.122x10­7 m2/sec and 4.897x10­5—6.529x10­5 m/sec using liquid waste of cocoa bean fermentation as solvent which depend on temperature and solvent concentration. Key words: Coffee, caffeine, decaffeination, leaching, mathematic model.

One of important steps in decaffeination process is steaming. The aim of steaming is to expand coffee beans porosity in order to obtain optimal condition for decaffeination process. Steaming can be done in single column reactor using saturated water vapour as media. The objective of this research is to study physical characteristics of coffee beans after steaming process using single column reactor. Material tested was Robusta coffee with 13—14% moisture content after dry processing. Reactor capacity is 6 kg dried coffee beans and 30 l water to produce water vapour. Dried coffee beans classified in 4 grades, i.e. diameter size (d) d>7,5 mm; 6,5<d³7,5 mm; 5,5<d£6,5 mm; and d£5,5 mm. Period of steaming process varied from 1 up to 3.5 hours. The result showed that the coffee beans expanded 8.6—9.5% in length, 12.2—13.3% in width, and 18.3—20.6% in thickness. Coffee bean volume increased 30—50%. Coffee bean moisture content increased f. Aritmatic diameter increased 8—13% while geometric diameter increased 9—18%. Sphericity not affected. Surface area increased 18—37%. True density increased 19—30% while bulk density was while. Porosity increased from 13—18% to 24—39% while coffee beans texture decreased from 323—384 g/1 mm to 212—225 g/1 mm. Color change increased from 14—20 to 38—40. The optimum steaming process was 3 hours.Key words : Coffee, steaming, single column reactor, decaffeination.