GB1045191A - Improvements in process for filtering fermented beverages - Google Patents

Abstract

In the final filtration of an alcoholic beverage such as beer, ale, porter, stout and wine, the alcoholic beverage is passed through a final filter consisting of a plastic membrane porous filter, the pores of which are smaller than yeast cells and small enough to prevent the passage of many bacteria, and there is quantitatively removed from the beverage all yeast cells and also bacteria to a residual amount below the threshold at which the bacteria can propagate in the negative conditions of the beverage due to the absence of yeast cells (which yeast cells in their presence and resulting metabolism can generate an environment which can assist the reproduction of bacteria); and unpasteurised, filtered beverage can for long periods be retained without spoilage in containers at ambient temperatures. The filter is formed of a continuous phase plastic sheet of cellulose nitrate or acetate about 150 microns thick with a multiplicity of pores in sizes from 0.22 to 1.2 microns occupying up to 80% of the sheet volume. The sheet is supported by a photo-etched stainless steel sheet having conically shaped holes (largest diameter 0.012 inch, smallest diameter 0.007 inch), which reduces the unsupported length of the porous filter to approximately 0.012 inch. The supporting sheets are in turn removably mounted in a series of disc filter plates stacked in a holder. The porous filter is used for the final filtration of beer and other alcoholic beverages at rates of between 1 and 20 United States gallons per square foot of filtering area per minute under an applied pressure of 10 pounds per square inch. Examples are directed to the final filtration of beer through plastic membrane porous filters of 0.8 and 1.2 microns pore sizes, respectively. The final filtration preferably is preceded by filtration through a microfibre glass filter.ALSO:A plastic membrane porous filter is formed of a continuous phase plastic sheet of cellulose nitrate or acetate about 150 microns thick with a multiplicity of pores in sizes from 0.22 to 1.2 microns occupying up to 80% of the sheet volume. The sheet is supported by a photo-etched stainless steel sheet having conically shaped holes (largest diameter 0.012 inch, smallest diameter 0.007 inch), which reduces the unsupported length of the porous filter to approximately 0.012 inch. The supporting sheets are in turn removably mounted in a series of disc filter plates stacked in a holder. The porous filter is used for the final filtration of beer and other alcoholic beverages at rates of between 1 and 20 United States gallons per square foot of filtering area per minute under an applied pressure of 10 pounds per square inch. The pore sizes are such that all yeast cells and sufficient bacteria are removed from the beverage to enable it to be retained without spoilage in containers at ambient temperatures.