Today in 1969, US Patent 3425839 A was issued, an invention of Michael Alan Pinnegar, assigned to Brewing Patents Ltd., for his “Continuous Beer Making Process Wherein the Wort and Yeast Are Separated by a Porous Partition.” There’s no Abstract, although in the description it includes this summary:
A potable beer is produced by circulating a body of yeast-containing liquor on one side of a partition and maintaining a moving body of wort on the opposite side of the partition. The partition is porous and has a pore size small enough to effectively bar the passage of yeast cells, but allows the passage of the soluble constituents of the wort and the soluble products resulting from the fermentation of the wort by the yeast.
The present invention relates to the production of potable beer by the fermentation of brewers wort by yeast in a continuous fermentation process. The term continuous fermentation process is used herein to refer to a fermentation process, in which brewers Wort is introduced in a stream into a fermentation zone. The stream of wort can be introduced at either constant or varying rates and may be continuous or discontinuous in the sense of being interrupted at constant or varying intervals. However in the generally preferred procedure brewers wort is introduced into the fermentation zone at a substantially constant rate over a substantial period of time e.g. not less than five days.