Note 6 — Chapter I · On the Intimate Relation existing between the Deterioration of Beer, or the Wort from which it is Made, and the Process of Brewing.

The initial temperature of the wort must be regulated by the quantity of wort subjected to fermentation. In English breweries, where large quantities are brewed at a time, the heat created by the action of fermentation would produce a temperature sufficiently high to affect the quality of the beer, if the yeast were added at 19° C. or 20° C.

The following are the temperatures at which the worts are pitched, in the principal London breweries:—For common ale, 60° F. or 15·5° C.; for pale ale, 58° F. or 14·4° C.; for porter, 64° F. or 17·8° C. The fermentation is commenced in large vats; from these the beer is run into vessels of a much smaller capacity, in which it completes its fermentation by working off the yeast and cleansing itself.

For white beer of superior quality, the temperature during fermentation must not rise beyond 72° F. or 22·2° C.; some brewers never allow it to exceed 18°C. (65° F.). The temperature is lowered by means of a current of cold water, which circulates through a coil fixed in the vats or other fermenting vessels.

In the case of porter, the initial heat of which is 64° F. or 17·8° C., the temperature in the vats sometimes rises to 78° F. or 25·5° C.; but such an increase in temperature excites considerable apprehension.

We have seen a tun for pale ale, containing 200 barrels of 36 gallons, pitched with 600 lbs. of fairly solid yeast. In forty-six hours the attenuation was considered sufficient, and the beer, which from an initial heat of 58·1° F. or 14·5° C., had risen to 72° F. or 22·2° C., was cleansed to working casks. The large vats in which the fermentation is started may be considered as equivalent to the cuves guilloires of French breweries, the casks in which it is completed and the yeast thrown off representing their 75-litre vessels, improperly called quarts. Notwithstanding the enormous English beer manufacture, and although the fermenting vat, as in making porter, for instance, sometimes attains the capacity of 2,000 to 3,000 litres (400 to 600 gallons), the casks into which it is run are never larger than 15 to 20 hectolitres (300 to 400 gallons); and even at Burton, in the celebrated breweries of Allsopp and Bass, the pale ale is finished in casks of a capacity less than 10 hectolitres, and yet the average turn-out of these immense works reaches 3,000 to 4,000 hectolitres (60,000 to 80,000 gallons) of beer per day.