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Advanced Brew In A bag (BIAB) Mashing Techniques
In a separate article called How to Make a Beer Mash, we’ll discuss the actual steps involved in the mashing process. In this piece, we’ll dig into some general information that every intermediate to advanced brewer should know about mashing. We'll also talk about mashing techniques that every brew in a bag or BIAB brewer should know in order to successfully make high gravity beers in kettles that have limited space.
Why Mashing Temperature Matters
Getting your temperature right when it comes to the mashing process is critical for any advanced homebrewer. That’s because it affects the fermentability of the wort since it helps determine how effectively you are breaking down the bonds in the starches in your malt.
That’s because during the mash, you are activating two kinds of enzymes – beta- and alpha-amylase – which are most active at different temperatures.
Beta-amylase is more effective at producing fermentable sugars in the wort and is favored when the mash temperature is between 140 and 149 degree F.
Alpha-amylase, on the other hand, leaves larger and more complex sugars in the wort that are less fermentable. The optimal mashing temperature for alpha-amylase is between 155 and 158 degrees.
Although each of these enzymes has a temperature range where they are most active, each will be active to a lesser extent on the fringes of that range. Just because you mash at 155 degrees, it does not mean that beta-amylase is entirely inactive, it means that alpha is more active than beta.
Because of these differences, brewers have devised different mashing techniques as a way to leverage the strengths of these enzymes in the wort by controlling the temperature at which you mash.
Mash temperature is a major factor in creating a dry beer vs. a sweet beer. Lower mash temperature = drier beer; higher mash temperature = sweeter beer.
In general, you will get sweeter, fuller-bodied beers if you mash at higher temperatures (156 to 158 degrees F) and drier, less full beer styles if you mash at lower temperatures (148 to 150 degrees F).
Step Mashing
While many newcomers to all-grain brewing hone their skills with one-step or single-infusion mashing, more advanced brewers may employ multi-step mashing.
Using a stepped approach to your mash allows you to tweak your wort to get your desired result – whether that be dry or sweet, velvety or lightly astringent – it’s the complexity of the sugars in the wort that determine the mouthfeel of your beer.
Stepped mashing is also useful for breaking down proteins (protein rest) which can cause beer haze, and for favoring compounds such as ferulic acid that can be converted into desired flavors and aromas during fermentation.
The goal is to begin your mash at a lower temperature – something like 110-113 degrees F – and then resting there for 10 to 20 minutes, at which point proteolytic enzymes are most active. After this, ramp up the temperature to the desired mash temp (between 140 and 160). By doing this, you are giving both kinds of enzymes – beta- and alpha-amylase – optimal conditions to do their work. This is also called “multi-step resting” or “protein rest” and it’s a common brewing technique in old-school European breweries to help achieve more clarity in the beer. This mash regime of 140 / 155 degrees also produces a far more fermentable wort.
Decoction Mashing
Perfected by German lager brewers at a time before thermometers and when malt was less modified than today, decoction mashing involves removing a portion of the mash, bringing that portion to a boil, and adding it back to the main mash to raise the temperature to the next desired temperature step.
While a single decoction is viable, some brewers use double or even triple decoctions in making their beer.
Advocates of decoction mashing claim it leads to a richer malt character by increasing the Maillard reactions that occur when you bake a cake or sear a steak. A toasted grain character is achieved because as the mash is heated to boiling, some of the sugars that are exposed to extreme heat on the bottom of the decoction pot are caramelized. We actually used decoction mashing when brewing our Banana Bread Brown Ale.
Parti-Gyle Mash
While not often employed in modern brewing, this mashing technique was standard operating procedure in England for centuries. The idea was to create multiple batches of sweet wort from a single set of grains – draining off the wort each time before refilling, heating, resting, draining and restarting.
It’s a great way to make use of fermentable wort that the sparging process may continue to create. And the advantage is by separating the mash into separate batches, you can achieve the kind of gravity you’re looking for in a finished beer.
Each kettle’s worth of wort would then be boiled and hopped separately before ultimately being combined in various ways to create different beers. For example, if your first mash (or gyle) is for a strong ale or barley wine, you could then follow up with another beer style with a lower ABV, such as a mild or a bitter.
Of course, to make this work, you would need multiple sets of equipment and plenty of fermentation space.
Liquoring Back
In general, a thicker mash (a lower water-to-grain ratio) will result in a thicker, chewier beer. It’ll also increase the alcohol by volume (ABV) of the final product. Brewing software makes it very easy to fairly precisely hit this target. However, another way to do it is by “liquoring back.” To do this, a brewer will essentially make a beer stronger than it needs to be by holding back some of the water that was potentially going to be added. After the boil, specific gravity can be measured and additional water can be added to decrease the specific gravity to the exact level desired.
This is also an extremely useful tactic for making high gravity batches of beer in brew in a bag (BIAB) systems where the full volume of water and grain may not fit in a single kettle. To do this, add all of the grain and as much water as possible without overflowing the inner grain basket or bag, and add the rest of the water required after grains have been pulled. We do this often when making stronger beers such as our Russian Imperial Stout Homebrew Recipe.
