Mild Ale: History, Brewing, Techniques, Recipes (Classic Beer Style Series) by Sutula Dave

Author:Sutula, Dave [Sutula, Dave]
Language: eng
Format: azw3
Tags: CKB007000 Cooking / Beverages / Beer
Publisher: Brewers Publications
Published: 2017-06-11T16:00:00+00:00

Boiling and Hopping

With only a few very esoteric styles of beer excepted, a properly conducted boil is essential to the brewing of all styles of beer. A vigorous, consistently maintained, and lengthy boil can very well make the difference between a world-class beer and a mediocre beer. Boiling destroys all the enzymes that are left over from the mash, in addition to stabilizing and sterilizing the wort. It extracts hop resins and isomerizes bittering alpha acids, concentrates the wort, coagulates and precipitates unwanted proteins, and lowers the wort pH for optimal fermentation. It also drives off harsh hop oils and off-flavor precursors like dimethyl sulfoxide (DMSO), which leads to dimethyl sulfide (DMS)—the signature cooked corn flavor found in Rolling Rock, which is not desirable in mild ale.

Boiling can commence as soon as the first wort covers the heated surface. In the case of direct-fired gas kettles, this is as soon as the wort fully covers the surface that is in contact with the flame. For steam-jacketed kettles, this is as soon as the wort covers the bottom steam jacket (if that jacket can be isolated). It is important to observe these details. There will be significant color pick-up and caramelization of sugars if the wort is allowed to sit against the heated surface and burn. This is actually desirable for some styles of beer (namely Scotch ale), and it might be an interesting exercise in a mild ale, but heating your kettle without any liquid in it is ill-advised because it tends to weaken the metal. This is especially true of direct-fired kettles where the temperature of the fire far exceeds the 230 °F (110 °C) that is common with steam.

The rate at which water evaporates from your wort is important in brewing mild ale because of the relatively delicate flavor profile of milds. In addition, the evaporation rate is indicative of the efficiency of the boil and how much of the off-flavor precursors and volatile hop oils, ketones, and sulfur compounds are being driven off. A rate of 10% evaporation per hour of boil is standard in the brewing industry. Anything more is gravy; anything less is inadequate.

A rolling, vigorous boil must be maintained for a minimum of 90 minutes. Isomerization, coagulation, and precipitation are not solely temperature-dependent—they also depend on agitation. At least 60 minutes of the boil should take place with the bittering hops. Extended boils of three hours or more will adversely affect hop utilization and tend to disassociate the coagulated proteins.

The pH of the wort at the beginning of the boil should fall between 5.2 and 5.5. A pH of 5.2 is best for protein coagulation and precipitation; a slightly more basic pH is best for hop utilization. In most cases, the transition to the more basic pH happens naturally due to the acidity of the brewing water, the additional acidification that comes from the use of dark malts, enzymatic activity, and the application of heat. If corrections need to be made, a food-grade phosphoric acid or calcium carbonate (gypsum) can be added directly to the kettle.

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