Patent GB-1006937-A (GB)
Title: Hop concentrate and process for the preparation thereof
IPC: C12C3/08
Filed: 1963-06-25
Abstract: The subject-matter is similar to that described in Specification 1,006,936 but the claims are directed to a process for the production of a hop concetrate for use in the manufacture of a hopped beverage which includes the steps: extracting the hops with an organic solvent at a temperature below 50  DEG C. in an inert atmosphere, isomerizing the hop resins of the extract by treatment with electromagnetic radiation, removing the solvent to concentrate the extract, separating hop oils and hop resins, and recovering selected hop oils and isomerized hop resins either for blending or for subsequent addition to wort or to beer during the brewing thereof.  The humulone resins of the hops may be isomerized to isohumulones, either after extraction of the hops or after extraction of the hops and steam distillation to remove substantially all of the volatile hop oils therefrom, by subjecting the hop extract in an inert atmosphere to electromagnetic radiation at a wave-length between 2000 and 7000 Angstrom units. The hop extract may be exposed in a glass reaction vessel for 4 hours to a battery of tungsten filament lamps operating at a colour temperature of 3400  DEG K.  In a modification, the extract is passed through an annular space in the centre of which are fitted a series of mercury discharge tubes emitting radiation at 3660 Angstrom units and above.  The residence time in the annular space is controlled by an ultra-violet spectrophotometer which continuously monitors the discharging isomerized extract.  Isomerization can also be achieved by using sunlight.  The selected hop oils and isomerized hop resin concentrate may be added separately to fermented and matured beer subsequent to wort boiling but prior to final filtration. The hop oil is dispersed in protein such as gelatin or in alginic acid, when added separately from the isomerized hop resin. According to an example, 50 lbs. of hops containing 6.4% of a -acid and 8.5% of moisture, and intimately mixed with 1 lb. of activated carbon, were extracted with trichloroethylene at 20  DEG C. in several stages and in an inert atmosphere of carbon dioxide. The extract was chilled and the precipitated hop wax was removed by centrifugation.  The extract, containing 3.21 lbs. by weight of a -acid, was then exposed in a glass reaction vessel (lower limit of transmission 3000 Angstrom units) to a battery of tungsten filament lamps operating at a colour temperature of 3400  DEG K. for four hours, by which time isomerization was complete. The solvent was removed through a commercial thin layer evaporator, leaving 14.2 lbs. of isomerized hop extract as an oily residue. The extract was diluted with 50 gallons of boiled out water and then steam distilled at 5 mm. of mercury absolute pressure by the direct injection of live oxygen-free steam to yield 0.4 lb. of oil.  Analysis of the residue indicated that basically all the oil had been removed.  Oil thus isolated was fractionated in a 40 plate column used with a reflux ratio of 10.  Two ounces of the resultant pot residue, which was essentially free of low boiling esters but contained 5% of myrcene and othei monoterpenoids, was added to the isomerized hop resins and emulsified.