GB871984A - Process for decaffeination of a soluble coffee extract - Google Patents

Abstract

An aqueous extract of roasted coffee is decaffeinated by subjecting it, while flowing in a thin film, to temperatures and pressures sufficient to strip the volatile flavour and aroma constituents therefrom, extracting the caffeine from the extract with a water-immiscible organic solvent, separating the extract and the caffeine-containing solvent and mixing the extract with the recovered volatile flavour and aroma constituents. Preferably, the extract film is agitated while in the form of a falling film distributed about the heated inner surface of a cylindrical evaporating chamber, the agitation being provided by means of radial vanes on a high-speed rotor within the evaporating chamber. This evaporation is carried out at the lowest possible temperatures. The present process enables the spraying of the aqueous extract under high pressure through a nozzle into a column of extract without developing a solvent/extract emulsion, the pressure being higher than normally used. The ratio of caffeine solvent to extract is lower than usual, the extract being decaffeinated by passing once through e.g. methylene chloride. Other organic water-immiscible caffeine solvents, e.g. benzene, a chlorinated hydrocarbon, e.g. dichlorethylene or trichlorethylene or ethylene chloride. Preferably an aqueous extract is prepared from roasted and ground coffee beans with a soluble coffee solids concentration from 20-35% and is introduced to an evaporator where it flows over the evaporating surface in an agitated thin film subjected to mild elevated temperatures less than 160 DEG F., preferably less than 140 DEG F. or even less than 100 DEG F. and reduced absolute pressures for 30 seconds or less to strip 20-40% by volume of the extract therefrom. The distillate is cooled to 55 DEG F. or less and is stored at even lower temperatures. The stripped extract is decaffeinated by means of any of the aforementioned solvents, e.g. methylene chloride, at 70 DEG F., preferably by a continuous liquid-liquid extraction but may be done in batches. If the extract has a lower specific gravity than the caffeine solvent, it is introduced as a spray at the bottom of a column and when the extract has the higher specific gravity it is introduced at the top of the column.