Probably the most important and easiest thing for a brewer to pay attention to is the mash temperature. There is a range of mash consistencies that will ensure conversion, and the pH will try its to keep itself in line (maybe with some nudging in the right direction), but temperature is wholly up to the brewer to control.
The most common mash schedules used is called “Single Infusion”. This is the simplest to do and require the least intervention by the brewer. Get the mash at the rest temperature and leave it alone by adding just one batch of hot water at the start, mix in the grains, and wait for conversion. The goal of this is to hit the desired mash rest temperature in one shot. Pretty simple, just activate the Beta/Alpha Amylase and let it do its thing.
Step mashing is where the brewer wants to have the different enzymes activated to do different work. Stepping up the temperature, making specific rests along the way to activate different done by either making additions of near boiling water to raise the temperature or by directly heating the mash tun.
Decoction mashing is probably the most difficult and time-consuming of the mash regimes. Decoction mashes are similar to step mashes in that different temperature rests are done, but the major difference is how these rest are met. To get from one rest temperature to the next, a portion of the thick mash (the grain portion—the enzymes are flooded out of the grains into the liquid portion, decoction mashes are generally a bit thinner in consistency to aid in this) is removed and boiled separately before being returned. This has a few effects, one being that it raises the temperature, it breaks down the grains to free more starches for conversion (increases efficacy, the sugars that are obtained form the grain in comparison to a laboratory theoretical maximum), and it adds compounds known as melanoidins—a family of flavour compounds developed from cooing sugars (not like caramel, but like searing a steak, or toasting bread). Some argue that decoction mashes aren’t needed to get the flavour compounds, that quality malt and a good recipe will do just as well, and modern malts don’t need to be decocted to get the higher efficiencies. So why do a decoction mash? My answer is to be traditional, experiment, and spend time doing a hobby that you enjoy.
To get to the temperatures needed for the mash usually hot water is added. If able, the mach tun may be heated between steps, but if not, hot water is the way (or decoctions between steps). Initial infusion, also called dough in, is the first mix of hot water and the grains. Concentrating on a single infusion mash, it would look something like this:
- First, the initial infusion called mash in or also known as dough in, is done. This is when hot water is mixed in the mash tun with the the grains. Because the mixing process will bring down the temperature, the water, called strike water, needs to be hotter then the intended mash temperature.
- The grains and strike water are mixed thoroughly so there no clumps or “dough balls” in the mash—if the grains are clumped up they aren’t going to convert. The mash is now left at temperature to convert, typically about an hour.
- Once conversion is complete, the mash temperature is brought up to cut off the enzymes and to make the lautering process easier. This is left for 10 minuets or so.
“NOTE: These equations also work for degrees Celsius, liters and kilograms. The only difference is that the thermodynamic constant of .2 changes to .41.
Initial Infusion Equation:
Strike Water Temperature Tw = (.2/r)(T2 – T1) + T2
Mash Infusion Equation:
Wa = (T2 – T1)(.2G + Wm)/(Tw – T2)
r = The ratio of water to grain in quarts per pound.
Wa = The amount of boiling water added (in quarts).
Wm = The total amount of water in the mash (in quarts).
T1 = The initial temperature (F) of the mash.
T2 = The target temperature (F) of the mash.
Tw = The actual temperature (F) of the infusion water.
G = The amount of grain in the mash (in pounds).”