Decaffeination of raw coffee beans

摘要

In decaffeinating raw coffee, the caffeine in an aq. soln.in the bean cells is removed from the raw coffee by means of a supercritical gaseous medium under normal conditions (1 bar, 20 deg.C). Process comprises (i) moistening the raw coffee to a water content of 35-50 wt.%, (ii) holding the moistened raw coffee under a gas atmos. of 75-300 bar at 20-80 deg. C for several mins. to several hours, (iii) suddenly or over a period of a few mins. releasing the gas pressure to a press. P of less than or equal to the critical press Pc of the gas and greater than or equal to 1 bar, so that the moist raw coffee does not freeze as a result of expansion cooling of the gas, (iv) rinsing the depressurised coffee beans with water to remove conc. aq. caffeine soln. from the surface of the beans and the edge zones; (v) repeating stages (ii), (iii) and (iv) several times; (vi) repeating the water rinse several times after releasing the press., (vii) catching the rinse water and recovering the dissolved caffeine, (viii) centrifuging the beans to remove residual aq. caffeine soln., and treating the recovered caffeine soln. to recover the caffeine, (ix) drying the still moist coffee beans to the necessary min. water content for roasting and (x) roasting the decaffeinated and dried coffee beans