There is no question that award winning beers can be made using malt extract as the the basis of their recipe. However, when using extracts, much of the work in converting the grain’s starches into usable sugars has already been done for the brewer. This also means that much of the control over the end product is in the hands of the extract producers and not the brewer. By using all grain and leaving malt extracts behind, brewers can take more control over the flavor profiles of the beers they are creating.
In all grain brewing, the malt extract is replaced by base grains. Base malts differ from specialty malts in that they contain enzymes necessary for converting the starches in the grain into sugars. This conversion ability is commonly referred to as the diastatic power of the grain. Specialty grains typically have little to no diastatic power while base grains have a larger diastatic index.
The process of converting starches into sugars and extracting them from the grain is known as mashing. Mashing is similar to steeping in that crushed grain is soaked in hot water for a period of time. A primary difference is that instead of extracting just color and flavor from the grain, enzymes are also being activated and converting the starches inside the grain into sugars.
Another key difference between steeping specialty grains and mashing is the importance of temperature. Different temperatures affect how enzymes convert the starches available in grain into sugars. By controlling the temperature of mashing, brewers can favor different enzymes and sugar conversions over others. The science behind these processes can get fairly complex, but the basic application for the majority of homebrewers actually ends up being fairly straightforward.
Typical mash temperatures range between 150F and 158F. In general, higher temperatures promote the production of more complex sugars while lower temperatures produce simpler sugars. Brewing yeast prefer simpler sugars to more complex ones. This means that mashing at a lower temperature produces a more fermentable solution whereas a higher mash temperature creates a liquid with a higher percentage of unfermentable sugars. If you want a sweeter beer, mash at a higher temperature. If you prefer a drier finish to your beers then mash at a lower temperature.
Techniques
There are also many different styles of mashing. The most common in homebrewing is the single infusion mash where all of the crushed grain is infused with water and held at a single temperature. More advanced techniques include multiple steps where the temperature is changed over the course of the mash by directly raising the temperature of the mash or adding more hot water at intervals. Another method known as decoction mashing removes a portion of the mash, heats it to a boil for a period of time, and then adds it back into the mash in order to raise the overall mash temperature.
Techniques for separating the liquid from the grain after mashing also vary. The procedure of separating the liquid from the grain is called lautering while rinsing the grain with additional water is called sparging. The most common methods of sparging include batch, fly, and no sparge. In batch sparging, a volume of hot water is added to the grain in one or more batches and then drained from the grain after it has been thoroughly mixed in. With fly sparging, hot water is slowly and continuously added at the same rate that it is being drained from the grain. Sparging can also be completely omitted by including all of the water directly in the mashing step.
Mashing Methods
There are a variety of ways to perform the mash. One popular technique is known as brew in a bag, or BIAB. It is often favored for its simplicity, requiring only a single large kettle and a nylon bag for mashing. The kettle must be large enough to hold the full pre-boil volume of water combined with all of the grain. To perform the mash, all of the water is first added to the kettle and heated to an initial strike temperature. This strike temperature will be slightly higher than the target mash temperature since the grain will absorb some heat. Next, the bag is placed in the kettle to act as a liner and the grain is mixed in. After 60 to 90 minutes of maintaining the mash temperature, the bag containing all of the grain is removed. At this point the mash is done and the boil can happen as usual.
While having a lower initial equipment cost and being fairly simple to execute, there are a few disadvantages to the BIAB method. Since there is no sparge step involved and the ratio of water to grain is high, the efficiency of starch conversion is less than with other methods. This loss of efficiency can be compensated for by increasing the amount of grain being used. Another challenge is the weight of the bag of soaked grain. The size of your kettle and amount of heavy wet grain that you can safely manage will be a limiting factor for the size of beers which can be reasonably brewed using the BIAB technique.
Another option for mashing is the partial or mini mash. This method sits in between extract brewing and using all grain by mashing a smaller amount of base grain and making up the remainder by using a small amount of malt extract. It is another good option for those wishing to keep additional equipment to a minimum. In practice it can be done in a similar fashion as the BIAB technique or normal steeping of specialty malts just with the addition of a few pounds of base malt. Some may prefer to use an insulated cooler for performing the mash in order to help maintain the mash temperature over the course of the mash.
The final class of mashing techniques requires a full set of additional equipment for brewing an all grain beer. Common setups involve either modifying a large beverage cooler to perform the mash in or using an additional kettle or pot. Typically, three vessels are required for a successful all grain brewing setup. At least one kettle for boiling and a second kettle or modified cooler for mashing is required. A third kettle called a hot liquor tank is also commonly employed to provide the hot water used for mashing and sparging. With careful planning, it is also possible to use only two vessels with perhaps a spare bucket as a temporary holding tank between mashing and boiling.