Abstract: 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.

Abstract: A method of providing a high quality iso-.alpha.-acid preparation is described. The method involves extracting a high quality primary extract containing .alpha.-acids from hops using liquid CO.sub.2 and isomerizing the .alpha.-acids in the primary extract. The liquid CO.sub.2 extraction is performed at a sub-critical temperature of not less than -5.degree. C. The primary extract contains .alpha.-acids, .beta.-acids, hop oil and usually no significant amounts of other organic compounds originating from the hops. In the preferred method the primary extract is not purified and the isomerization is performed by boiling an alkaline solution of the extract. This boiling can be utilized to remove the hop oil. The .beta.-acids can be readily removed by acidifying the solution of iso-.alpha.-acid and filtering off the precipitated .beta.-acids. The iso-.alpha.

Abstract: A method of providing a high quality iso-.alpha.-acid preparation is described. The method involves extracting a high quality primary extract containing .alpha.-acids from hops using liquid CO.sub.2 and isomerizing the .alpha.-acids in the primary extract. The liquid CO.sub.2 extraction is performed at a sub-critical temperature of not less than -5.degree. C. The primary extract contains .alpha.-acids, .beta.acids, hop oil and usually no significant amounts of other organic compounds originating from the hops. In the preferred method the primary extract is not purified and the isomerization is performed by boiling an alkaline solution of the extract. This boiling can be utilized to remove the hop oil. The .beta.-acids can be readily removed by acidifying the solution of iso-.alpha.-acid and filtering off the precipitated .beta.-acids. The iso-.alpha.

Abstract: The bubbling of poorly soluble gases into fermentation liquids either for the replenishment of dissolved oxygen or for removal of excess super-saturated CO.sub.2 can lead to severe foaming problems, particularly in deep fermentation vessels. The present invention overcomes this problem by dissolving the gas in an aqueous medium, usually water, under superatmospheric conditions and injecting the gas solution into the fermentation liquid in controlled quantities under conditions such that the gas is either retained in solution in the fermentation liquid or, at most, the gas is released from solution in the form of microbubbles of much smaller size than can be obtained by passing gas through a porous diffuser. Microbubbles may be released from the gas solution by injecting the pressurized gas solution into the fermentation liquid under conditions of high shear rate.

Abstract: An improved method of making hop oil is described involving steam distilling the hop oil under vacuum at a temperature not exceeding 50.degree.C. The distillate can be collected by cooling to less than -20.degree.C. The collected distillate or hop oil extracted therefrom can be used in beer making processes to give beer having a hop character very similar to that obtained by dry hopping.