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Mashing
Mashing Systems
Infusion Mashing
The traditional method of mashing is the infusion process, in which brewers produce and recover the extract at a single mash temperature, called the "conversion temperature." It is most commonly associated with the production of ales and stouts, and is also successfully used by some lager brewers. It is the most widely used method by craft breweries because the vessels are simple, inexpensive, and easily scaled to their low output.
Temperature-Controlled Mashing
Sometimes referred to as "step-infusion," this mashing procedure involves a series of rests at various temperatures. It involves a protein rest and in some cases even an acid rest. The modified-infusion method mimics the traditional decoction-mash sequence, but with less satisfactory results (primarily because no part of the mash is ever boiled). One advantage of step mashing over single-temperature mashing is that both specific enzyme activity and fermentability of the wort can be promoted by controlling the temperature and duration of stands at selected points. It also allows a higher extract yield, a 4 to 5% increase in extract over that obtained from a single-temperature mash (34). Some brewers believe that step mashing is more effective than a single-infusion mash in dealing with under-modified malts, such as German and Belgian malts.
Decoction Mashing
Decoction mashing is the traditional method used in the production of wort for bottom-fermentation beers and is most commonly associated with the production of lagers in Germany. It was developed largely as a result of the use of under-modified or enzymatically weak malts. This system involves removing a portion of the mash (the decoction) for boiling and returning it to the main mash to increase the temperature. Decoction mashing involves one-, two-, or three-decoction steps, which are referred to as single- two, or three-decoction mashes. The choice of the number of decoctions and the duration of the boil provides control over protein coagulation and malt sugar composition.
Single-Step Decoction Mashing: The single-step decoction involves only a saccharification rest. The entire process usually takes about 2 hours. As with the other decoction systems, there are many minor variations of the single-step mash system.
Two-Step Decoction Mashing: The two-step decoction involves only protein and saccharification rests. The entire process usually takes 2 to 3 hours. As with the three-step decoctions system, there are many minor variations of the two-mash system, especially with regard to speeds of heating, the rate at which the decoction part of the mash is mixed with the main mash, and the lengths of the stands.
Three-Step Decoction Mashing: The three-step decoction involves acid, protein, and saccharification rests. The overall processing time is about 6 hours from mashing-in to lautering. There are many minor variations on the classical triple-decoction mash, especially with regard to speeds of heating, the rate at which the decoction part of the mash is mixed with the main mash, and the lengths of the stands.
Double-Infusion Mashing
The double-mash infusion system is the most widely used system in North America. This system prepares two separate mashes. It utilizes a cereal cooker for boiling adjuncts and a mash tun for well-modified, highly diastatic malts. Most adjuncts must be boiled separately to gelatinize the starch. If pregelatinized adjuncts (e.g., flakes) are used, no boiling is required in the cereal cooker. In this case, the flakes can be added directly to the mash tun during or at the end of the protein rest (9).
The double-mash infusion system was developed to utilize adjuncts as a source of cheaper extract and as a means of producing the lighter, less-satiating beers that have traditionally found favor with North American consumers. Rice and corn are mostly used as adjuncts, though barley, wheat, and sorghum are used to a limited extent. Sugar and syrup are also used as a source of extract, but they are added directly to the kettle, not the cereal cooker.
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