Brewing Patents Limited

The Brewing Research Foundation

Alfred G Wheldon

Derek R Laws

Nigel A Bath

Colin S Ennis

John Anthony Pickett

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.-acid preparation is of outstanding purity and can be added to beer after fermentation and in particular to bright beer after final filtration to provide bitterness.

Production of an iso-.alpha.-acid preparation from hops

A method of preparing a hop extract is described in which liquid carbon dioxide is passed at a temperature of from -5.degree. C. to +15.degree. C. through a column of hop material to extract .alpha.-acids contained therein. The method gives a primary extract which is of much higher purity than has been previously described particularly in comparison to presently commercially available solvent extracts.

Hop extraction with carbon dioxide

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.-acid preparation is of outstanding purity and can be added to beer after fermentation and in particular to bright beer after final filtration to provide bitterness.

Growing community of inventors

Galley Wood, United Kingdom

Alfred G Wheldon