Brewing Patents Limited

Charles D Baker

Derek R Laws

A method of purifying aqueous solutions of iso-.alpha.-acids by removing .beta.-acids therefrom comprises first bringing the solution to an iso-.alpha.-acid concentration of 0.5% to 10% .sup.w /w, particularly 0.5% to 5% .sup.w /w, then reducing the pH to a value in the range 7 to 10, preferably 8 to 9, so as to form an easily filtered precipitate of .beta.-acids. Preferably pH reduction is effected by bubbling carbon dioxide through the solution. The separated iso-.alpha.-acid solution may be concentrated to an extent that a phase separation takes place into two aqueous phases one of which has a higher iso-.alpha.-acid concentration than the other. The recovered iso-.alpha.-acid solution is suitable for direct addition to beer without haze formation.

Method of purifying iso-.alpha.-acids

A method of making an aqueous composition containing iso-.alpha.-acids by isomerizing .alpha.-acids, preferably obtained by extracting hops with liquid carbon dioxide or organic solvents, in an aqueous alkaline medium is characterized by providing one or more salts in solution in the isomerized reaction mixture at a molar equivalent concentration greater than that of the iso-.alpha.-acids, whereby the reaction mixture separates into an oily phase and an aqueous phase, the oily phase containing a higher concentration of iso-.alpha.-acids than the aqueous phase, and recovering an aqueous composition containing iso-.alpha.-acids by separating the oily phase from the aqueous phase. The preferred salt is potassium carbonate which also provides a suitable pH for isomerization.

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Uttoxeter, United Kingdom

Charles D Baker