Patent GB-1006936-A (GB)
Title: Hop concentrate and process for the preparation thereof
IPC: C12C3/08
Filed: 1962-06-25
Abstract: <PICT:1006936/C6-C7/1> A hop concentrate for use in the manufacture of a hopped beverage is prepared by extracting hops under an inert atmosphere e.g. of carbon dioxide and at a temperature below 50  DEG C. with an organic solvent consisting of a simple aliphatic alcohol, an aromatic hydrocarbon, low-boiling petroleum fractions, or a chlorinated aliphatic hydrocarbon, removing the solvent to obtain a crude hop concentrate, steam distilling the concentrate to separate volatile hop-oils and non-volatile hop-resins, fractionally distilling the hop-oils and collecting fractions containing terpene and sesqui-terpene compounds with taste and flavour characteristics suitable for beer, isomerizing the humulones contained in the non-volatile hop resin by treatment with alkali, concentrating the isomerized resins by removal of water and residual solvent, and blending the collected fractionally distilled hop-oils and isomerized hop-resins to obtain a blended hop-concentrate final product.  The process is depicted in Fig. 1. The preferred conditions of operation are as follows: The solvent for the solvent extraction is trichloroethylene, methanol, benzene or petroleum fractions, the solvent is evaporated under vacuum in a thin-layer type evaporator and the vacuum is adjusted so that the solvent used for extraction is removed at temperatures near to ambient temperatures, the hop extract is steam distilled with live steam for 4 hours at a pressure between 20 to 30 mm. Hg. and at temperatures between 15 to 30  DEG C., hop oil is fractionally distilled in a fractionating column at a pressure of 100 mm. Hg. and the fraction which boils above 100  DEG C. at 100 mm. Hg. is re-fractionated at a pressure of 100 mm. Hg. and the distillation is continued until a continuously monitoring gas-liquid chromatograph indicates that the ratios between the hop-oil components in the distillation receiving vessel approaches that of a conventionally brewed beverage, the alkali is added continuously to the resin residue of steam distillation while the residue flows through alternate zones of heating and chilling maintained at 105 DEG C. and 5  DEG C. respectively, to ensure a minimal residence time of heat-sensitive humulones of the hop resin in the heating zone, and the alkaline isomerized hop resin of specified pH is neutralized with hydrochloric acid.  Thus, the humulones may be isomerized by adding cold pre-boiled 0.25% sodium hydroxide solution to the resin residue of steam distillation until a pH of between 8 and 9 is attained, then further adding 0.25% sodium hydroxide solution while passing the resin residue through alternate zones of heating and chilling, until the pH is between 10 and 12, or the humulones may be isomerized by adding 10% sodium carbonate solution to the hop resin residue of the steam distillation until a pH of between 7 and 8 is obtained while maintaining the residue under reflux, adding a further quantity of 10% sodium carbonate solution to the refluxing alkaline residue until a pH of between 8 and 11 is attained, and continuing refluxing of the alkaline solution to convert the humulone to the di-anion, chilling and finally neutralizing the alkaline solution. In the particular example, isolated hop resins were freed of essential oil either by the direct injection of live oxygen-free steam or by boiling with pre-boiled water under an oil trap with cohabation.  The isolated oil was fractionated under reduced pressure using a 40 plate column with a reflux ratio of 10.  The isomerized resins are concentrated by vacuum distillation.