Let's brew a Bock! I'm using a Grainfather brewing system, essentially a giant computerized electric kettle with an integrated mash tun and a pump at the bottom. The process is similar to when I brewed with a big pot on a stove and a modified cooler for mashing, just automated.
Step one, add the "strike water" (what we steep the grain in) and heat it to 68C, the temperature we need to "mash" the grain (essentially steep it like with tea).
As the water heats up I drop in the mash tun insert. It has a perforated bottom that prevents most of the grain from getting through, and it plus the barley husks in my mash ultimately act as a filter so only liquid gets through as we recirculate it.
Now we add our pre-crushed malted barley to the water a bit at a time, stirring in between. This process is called "douging in" and you are basically making a giant barley porridge.
Now we mash for an hour. The pump recirculates liquid through the grain. Enzymes (alpha and beta amylase) in malted barley convert starches into sugars (maltose and glucose). Each enzyme has different but overlapping ideal temp ranges to convert starch, both are active at 68C.
While I wait for the mash to complete, I take notes in a notebook I've used for years to track my brewing. This makes it easier to repeat beers I like, and review my notes if something doesn't work out.
Halfway through the mash you can see the effect of recirculating liquid through the grain. The husks and perforated bottom are filtering as they should and the cloudy liquid from 30 minutes ago is much clearer.
One the mash completes, we start the "mash out" step. This heats what we can officially call "wort" (pre-beer or sugary barley liquid) up to 75C to denature the enzymes and stop the creation of any more sugars. This also makes it easier to rinse out more sugar in the next step.
Now we "sparge" or rinse the remaining sugar out of the grain with 10L of 75C water in 1L batches from my electric kettle. The internal grain basket lifts out and rests on top of the kettle so wort and sparge water can drain into the boil kettle that is heating up to 98C.
The boil! This recipe calls for a 90min boil but most are 60 mins. We boil wort for a few reasons:
1. Cooking. Maillard reactions develop flavor in the wort
2. Sterilization. Wort is sticky, sugary stuff. Boiling kills microorganisms in the barley that'd infect the beer.
3. Boiling coagulates protein solids out of solution you don't want in the beer.
4. Boil off other compounds you don't want into the air. This boil is 90mins in particular to give more time to boil off di-methyl sulfide (DMS) in the wort.
5. Bittering with hops (next step).
Adding hops with 60 mins left in the boil. Hops boiled this long produce a bitter flavor and are called "bittering hops". Originally hops were added because it extracts an antibiotic oil, lupulin, which helps prevent infection in the beer, particularly before alcohol is present.
Cleaning part 1! While we wait for the boil to finish it's a great time to clean up equipment we aren't using for the rest of the process.
Ten minutes before the end of the boil I connect my counterflow chiller to the pump and recirculate boiling wort through it. Up to now we haven't been concerned with sterilization but after the boil everything the wort touches must be sterile including inside this chiller.
We must cool the wort to room temp so we don't kill the yeast we add later. The Grainfather comes w/ a counterflow chiller that makes this fast. Pump hot wort through 1 tube, cool water the other. Heat exchanges inside, cool wort goes back to the kettle, hot water to a bucket.
How do I know when the wort is cool? I have an inline thermometer connected to the wort output on the counterflow chiller.
Now that it's cool, I move the counterflow output to my fermentation vessel (a keg) and let the pump transfer it. The keg was sterilized with iodophor solution and the exhaust water from the counterflow chiller. Fun fact: iodophor is on the official list of coronavirus killers!
Once the fermenter is almost full, I pitch the yeast. I also sprayed the outside of the yeast container with sanitizing solution about 10 minutes before I opened it so the outside was sterile.
Full and ready to go in the fermenter.
This is a lager so I will ferment it at celler temperatures in a warm fridge (~10C). I have attached a tube to the keg inlet so CO2 the yeast exhausts will bubble out in a jar of sanitizing solution. It takes ~ a month to ferment, another month lagering before ready.
@kyle interesting. Never fermented in keg (have used buckets but usually use glass carboys). Some get extra active like Belgian Quads, so having a blow-off tube option is handy.
@kyle thank you for this excellent content 😁