Brewing Patents Limited

The Brewing Research Foundation

Derek R Laws

John Anthony Pickett

Nigel A Bath

Colin S Ennis

Alfred G Wheldon

Charles D Baker

Frederick R Sharpe

Christopher M Grimmett

A method for the production of isomerized hop preparations comprising admixing whole or powdered hops with a solid or aqueous alkali or alkaline earth metal salt. The invention provides that the resultant admixture is simultaneously subjected to a pressure of at least 2 Kg/cm.sup.2 and at a temperature of at least 80.degree. C. in a closed vessel, thereby to form a hop preparation high in iso-.alpha.-acids and with substantially undegraded hop oils. The closed vessel is preferably an extrusion cooker.

Method of producing isomerized hop preparations

Hop extract containing a high proportion of a desired constituent, hop oil, .alpha.-acids or .beta.-acids, is formed by extracting hops with pressurized fluid carbon dioxide, collecting separate fractions of the extract obtained at different times, and selecting the fraction having a high proportion of the desired constituent. Fractions containing (a) at least 70% of the available hop oil at at least 10% concentration, and (b) at least 25% of the available .alpha.-acids at at least 55% concentration, may be obtained in a single process by extracting initially at a lower temperature in the range 0.degree. C. to -57.degree. C. and subsequently at a higher temperature in the range -5.degree. C. to 31.degree. C.

Preparation of hop extracts rich in particular constituents

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 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.

Production of iso-.alpha.-acids

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.

Production of iso-.alpha.-acid

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.

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Bexleyheath, United Kingdom

Derek R Laws