Step Mashing: Tips from the Pros
Brewer: Lee Chase, Stone Brewing Company in Escondido, CA
Step mashing is a technique that starts at a lower temperature rest, then is “ramped up” or heated at a certain rate (degrees per minute) and allowed to rest at selected temperatures. The graphing of such a mash, using time and temperature on the axis, creates plateaus or steps, hence the term step mashing.
This method of mashing allows you to manipulate your malt to create a desired spectrum of substrate in the wort by focusing on the optimum temperature of different enzymes. There are primarily three rests that we focus on here at Stone and these accommodate the following enzymes: proteinase, beta-amylase and alpha-amylase.
The important thing to consider is that each of the enzymes has an optimum temperature, meaning they will tolerate higher or lower temperatures, but won’t work as effectively. At lower temperatures they work slowly and they work faster as the temperature increases. As the temperature reaches an enzyme’s threshold temperature range, the enzymes will denature and cannot be “re-natured” by cooling back down.
In a standard infusion mash, you would try to rest at a selected temperature, usually something that allows for both the alpha-amylase and beta-amylase enzymes to break down the starch into fermentable sugars. Because beta-amylase creates fermentable sugars exclusively, you may want to lean toward the beta-amylase optimum temperature if you want a more fermentable wort with a lower terminal gravity.
Conversely, if you are looking for a beer with more body, you may want to move your mash rest to focus on the alpha-amylase, which breaks the starch into smaller pieces, but not necessarily to fermentable-size chunks. Alpha-amylase is able to take a starch and break it into a lot of smaller pieces, but those are not fermentable in size. The benefit comes when beta-amylase work to make fermentables, while the alpha-amylase creates “loose ends.” When this happens you can get fermentable sugars without too many large pieces of dextrin.
Beta-amylase functions optimally between 140–149 ºF (60–65 ºC) and is quickly denatured at 158 ºF (70 ºC). Alpha-amylase functions optimally between 162–167 ºF (72–75 ºC) and is denatured at 176 ºF (80 ºC). The key word here is “optimally,” and there is some gray area in between.
If you have to choose between treating your alpha-amylase optimally (which will denature your beta-amylase), or treating your beta-amylase optimally, we choose the beta-amylase here at Stone. They give us the fermentable sugars. The alpha will still work at the lower temperature, but the beta will not work at the higher temperature.
Since we are considering a step mash, which always ramps upwards in temperature, we can rest our mash at the optimum temperature for both of these enzymes just to feel good, but most of the action on the starch is going to be done at the lower rest temperature.
However, our malt has the power to help us out: it has enzymes to break down the beta-glucan and protein, which will lower the viscosity of the wort, making the run off and filtration of the finished beer much easier. Also, with a high portion of wheat (which is husk-less), you will lose out on husk material, which acts as a filter bed and also makes run-off easier.
To put these enzymes to use, start your mash at the temperature for the enzyme with the lowest optimum temperature. The most common is the protein rest at 122 ºF (50 ºC). This temperature allows for proteinase enzymes to degrade protein. The length of time you rest at this temperature depends on what you are trying to achieve — the more wheat or protein in the mash, the longer you may want to rest. Most of the action happens pretty quickly — I’d give it no more than 30 minutes.
From the protein rest, you would add heat, stirring vigorously to get an even temperature rise throughout the mash. Be careful not to raise the temperature past your target rest temperature or you will denature the enzymes. Most likely, your next target will be at 144 ºF (62 ºC), which allows for optimum beta-amylase, as well as some slower-but-active alpha-amylase action.
Brewer: Craig Burge, Sprecher Brewery Company in Milwaukee, WI
Generally speaking, I believe by using a step mash program versus an infusion mash, this enables the brewer, professional or amateur, to more accurately brew many more styles of beer. In infusion mashing you are usually limited to a single temperature and only one conversion step (saccharification), whereas in step mashing you have unlimited options for changing time, temperature and rests to suit the needs of the particular style you are brewing.
Appearance is a very important factor in brewing. Infusion mashing typically means you will be dealing with plenty of protein hazes in your finished product due to the absence of the proteolysis rest, though it is worth noting that there is some controversy around this view (i.e. all brewers, whether infusion or step mash, risk haziness in beer if they do not take the necessary precautions.) In any case, the limited filtering capabilities of most homebrewers can be addressed to a certain degree through step mashing. In my opinion, even if you are using all well-modified malts, you should have at least some sort of protein rest to help with chill hazes and head retention.
The protein rest is also where you let the beta-glucanase enzyme degrade any beta-glucan gums. By doing this it decreases the wort viscosity and makes the lautering process easier.
If you are currently an infusion masher, you should be used to using mostly well-modified malts. Well-modified malts are those that have had significant enzymatic degradation during the malting process. Step mashing gives some leeway and opens the door to both well-modified malts and under-modified malts (and all of those in between) — allowing for conversions that were not completed in malting to happen during the mash. Step mashing takes care of this with a low temp rest around 118–120 ºF (48–49 ºC).
These days, most of the base malts you can use are well-modified, which means they are suitable for either step or infusion mashing. Step mashing even allows you to add well-modified malts later in the mashing process to avoid over conversion/degradation. Brewing good beer is all about the details and step mashing is a great example of this!
