GB1056693A - Freeze-drying of granular coffee extract - Google Patents

Abstract

A body of an aqueous coffee extract is frozen, subdivided to obtain granular particles resembling roasted and ground coffee, said particles having a size wherein at least 97 wt. per cent is retained on an 80 mesh U.S. standard sieve screen, and preferably at least 90 wt. per cent on a 40 mesh screen, and subjected to freeze drying, preferably under a vacuum of less than 500 microns. Desirable aromatic constituents removed from freshly roasted and ground coffee may be added to the aqueous extract prior to freezing. The under 80 mesh particles, and preferably also the under 40 mesh particles may be removed from the subdivided material and added to a subsequent body of liquid extract as freezing commences to provide seeds. The extract preferably contains 20-70% soluble coffee solids, and may be frozen to below its eutectic point at a rate sufficiently slow to form a non-ordered distribution of dendritic ice crystals in the eutectic mixture, no discrete non-dendritic ice crystals being present. In order to decrease the bulk density of the dried particles, they may be agglomerated by rendering their surfaces tacky, for example by contacting with steam or with wet droplets of the coffee extract.