Mashing
Mashing is a step in the brewing process that combines crushed Malts with hot water to convert complex starches into simple sugars that are more readily fermented. There are many variations of mashing, but the single infusion mash described below is easily done with home equipment, and suitable for most popular beer styles. During the malting process barley grains develop many enzymes that are needed for mashing. These enzymes, when heated with water in the mash, react with the starches in the malt and produce maltose. Maltose is a favorite food for yeast during fermentation. A related process called lautering runs hot water through the grain bed after the mash to extract the sugars and produce a sweet liquid called wort for brewing.
Types of Mashing
The most popular mash profile among homebrewers is the single infusion mash, but several methods can be used to mash and all are accessible by the homebrewer.
Single Infusion Mash
The Single Infusion Mash, also called the British Infusion Mash is the simplest mashing method for homebrewers to use. In an infusion mash, room temperature crushed grains are combined with a premeasured amount of hot water at a fixed temperature. By accurately calculating the volume and temperature of the water, one can reach a target temperature for the combined mash in the 148 to 158 F range. Infusion is typically done at a water to grain ratio of around 1.25 quarts per pound of grain. The easiest way to calculate the proper infusion volume and temperature is with an infusion calculator or brewing software such as BeerSmith. The mash is then held at that temperature usually by keeping the mash in an insulated cooler for 45-90 minutes. At this temperature, the mash will readily convert starches into sugars. You can test for conversion of sugars using an iodine test. Simply draw a small quantity of mashed grains out, add a few drops of iodine to it. If the iodine does not turn blue, then the conversion is complete.
Temperature Mash
An alternative to the infusion mash is the temperature mash. Rather than adding a known quantity of hot water, the mixed water and grains are simply raised to the target mashing temperature and held at that temperature until the starch conversion is complete. While this is quite practical for a commercial brewer, temperature mashing presents challenges to home brewers. Most homebrewers use simple pots over a stove or propane burner, and it is difficult to hold a precise mashing temperature for an extended period using just a stove and pot.
Decoction Mash
A third technique traditionally used in Germany for many beer styles is decoction mashing. In a decoction mash, a quantity of mash including both grains and water is moved to a second container where it is brought to a boil. The boiling mixture is then added back to the original mash to raise the temperature of the overall mash. Again, a calculator or brewing software is needed to accurately calculate the correct volume to decoct. Traditional decoctions were typically done at higher water to grain ratios of 2.0 qt/lb or more. More modern techniques often use water to grain ratios closer to the 1.25-1.5 qt/lb range.
Multiple Step Mashes
Though a single infusion mash is suitable in 95%+ of cases where modern well modified malts are used, some precooked adjuncts and undermodified malts require protein rests at lower temperature before the main saccrification (sugar conversion) step in the mash profile. These protein rests help to break down complex starches in preparation for saccrification. Infusion, temperature and decoction steps may be combined to achieve multiple step mashes. For example a complex three step decoction mash might start with an initial infusion step to an acid rest at 105 F, followed by a protein rest at 122 F, and a saccrification step at 155 F. In many mash profiles, a mash out step is used to raise the temperature of the entire grain bed in preparation for sparging. The mash out step helps to halt saccirifcation, and also helps ensure an efficient sparge by extracting sugars at a higher temperature.
Mash Temperature
The temperature of mash steps, particularly the main sugar conversion (called the saccrification step) can have a significant effect on the character of the beer. Lower temperature conversion - around 148-152 F will take longer but will produce a more complete conversion of complex starches to sugars resulting in more fermentation and a clean, lighter tasting beer. A high temperature conversion of 155-158 F will result in less start conversion leaving a beer with more unfermentable dextrines. This will create a beer with a full body and flavor. Middle mash temperatures (153-156) will result in medium bodied beers.
Sparging
After the mash process is complete, the grains, water and sugar are still in suspension in the mash container, called the mash tun. The sugars are separated from the grains in a process called sparging (alternately called lautering). The mash tun typically has a false bottom or screen at the bottom with a spigot that allows the brewer to draw run-off from the bottom of the grain bed. Hot water at approximately 178 F is slowly added to the top of the grain bed, run through the bed, and drawn off the bottom through the false bottom and out the spigot to the boiling vessel. This extracts sugars from the grains and produces sweet liquid wort for boiling. The initial runnings (first few quarts) drawn during the sparge process are recirculated back through the grain bed, as the early runnings often contain grain husks, crushed material and other undesirable elements. After the initial runnings, the grain bed will act as a filter and reduce the cloudiness of the runnings. Sparging is best done slowly so that a maximum amount of sugar can be extracted from the spent grains. The sparged wort is transferred to a boiler where hops is added and the mixture boiled before cooling for fermentation.
See Also
External Links
- BeerSmith Brewing Software - a tool that will do your infusion and decoction calculations
