| 摘要 |
In the production of a fermented malt beverage, such as beer and ale, a dilute wort having an extract of less than 11 DEG Balling is made by preparing a malt mash, heating the mash, filtering the mash to produce a wort and boiling the wort in a brew kettle, utilizing 1.3-5 barrels of water per 100 pounds of brew materials, and the dilute wort is freeze concentrated, preferably to remove between 30 and 80 weight per cent of the water, to obtain a concentrated wort which can be readily fermented. (One barrel is stated to be the equivalent of 31 United States gallons.) The wort may be concentrated to a level greater than that desired for fermentation and thereafter diluted with water to the relatively lower extract level, between 11 and 13 DEG Balling, desired for the fermentation. The freeze concentration can be carried out batchwise using a plurality of alternate ice-generators and centrifuges connected in series. Alternatively, there may be employed a continuous two or three stage fractional crystallisation which involves cooling the dilute wort to produce a slurry of ice crystals and mother liquor, melting the crystals, passing at least a portion of the melt in contact with and counter-current to the crystals, and separating the mother liquor (concentrated wort) and the melted ice. The dilute wort may be freeze concentrated to remove 75 weight per cent water by cooling it to -4.4 DEG C. to form a slurry of ice crystals in mother liquor, passing the slurry (with 50 per cent ice solids) to a first crystal separation column to separate the ice crystals, cooling the mother liquor to -10.8 DEG C. to form a second slurry of ice crystals, passing the latter slurry (with 50 per cent ice solids) to a second crystal separation column to separate ice crystals, and withdrawing from the latter column the resulting mother liquor (concentrated wort). Hop flavour and aroma derived from extracted hop resins and hop oils are imparted to the beverage by adding hop extract to the wort subsequent to boiling of the wort in the brew kettle, such as to the wort cooled after the boiling, or to the fermented brew e.g. after finishing. The fermented brew itself may be freeze concentrated and the concentrate reconstituted by the addition of water and carbon dioxide; hop extract may be added to the concentrate or to the reconstituted product. The amount of hop extract is preferably sufficient to provide the finished beer with 275 p.p.m. of hop resin and 0.3 p.p.m. of hop oil. A small amount of hops may be added additionally to the wort and boiled therewith to assist in precipitating undesired proteins of high molecular weight, though the freeze concentration of the dilute wort and of the fermented brew promotes or causes the precipitation of such proteins and polysaccharides. The preparation of adjunct-containing malt mashes and worts is described in detail. After boiling, the wort can be strained to remove hops (if added during the boiling) and precipitates, and the pH can be adjusted by the addition of 0.3-0.5 per cent of potassium sulphate, potassium phosphate or lactic acid to maintain the pH at about 5 to 6. |
