Iowa's Most Historic & Award-Winning Micro Brewery
BREW DAY - The Fun Part Is Brewing!
Brew days start at about 8am by first grinding in the malt.
We dump the malt into the auger, which feeds it to the mill.
The mill setting is very important. We grind the base malts find enough to yield the maximum extract without dissolving the harsh tannins in the malt. We also have to be careful not to destroy the kernel hulls. Different malts and wheat are ground at different settings.
The mash/lauter tun has a metal screen in the bottom of it. This screen is fine enough to keep the grain from passing through. When conversion is complete, we begin what is know as the vorlauf, a German term referring to recirculation of the unfermented liquid, known as wort (another German term). We pump the liquid back over the grain bed in the mash/lauter tun until the fibrous material in the grain bed (the kernel hulls) is compacted enough to form a filter. This natural filter allows the extract, or wort, to "run off" clear. This process takes about 15 minutes.
Then we run the clear wort off into the kettle through a very small tank known as the grant, The grant serves as a staging vessel to allow for the consistent accumulation of wort and to monitor its clarity and density. The grant acts as a buffer-zone to prevent the wort from flowing so quickly it over compresses the grain bed. If the grain bed becomes too tight, the rate of run-off will slow, or stop completely.
It requires about 1.5 to 2 hours to fill the kettle. During which time, the density of the wort (its gravity) or the concentrations of sugar present is monitored to ensure the proper gravity when the kettle is full.
Once the kettle is full, we push the spent grains out into a tip dumpster. From there, they are dumped into a farmer's trailer and they use the spent grain as filler feed for his livestock.
When the kettle is full, the wort is brought to a boil. We boil the wort for a full hour to an hour and a half depending on the brew. At the beginning of the boil, we add hops high in bitterness because it takes longer to extract the bitterness. Later in the boil, we add other hop varieties that are more aromatic. The aroma boils off quickly, so we do not want to add them too soon.
The boiling also sterilizes the wort and breaks down large proteins. THe boil also evaporates sulfur compounds, which are not conducive to good beer.
After the boil is complete, the wort is "whirlpooled" in the kettle. The protein compounds coagulate to form a substance no one wants in their beer so we pump the wort out of the bottom of the kettle. It then goes back in through a tangential valve back into the kettle, causing it to spin. The centrifugal force piles the solids now present in the wort at the bottom of the kettle in a neat pile.
The wort is now drawn off the bottom of the kettle and pumped through the heat exchanger. This cools the wort by passing over many stainless steel plates with cold water and chilled antifreeze on the other side. We cool our wort to 55 - 75 degrees Fahrenheit depending on the type of yeast we use. Lager yeast ferments at the colder temperatures while ale yeast strains ferment much warmer. We also add oxygen, as yeast cells require it to grow and multiply.
The wort, with yeast and oxygen, is pumped into a fermenting tank in our cellar. Here primary fermentation takes place. It remains here for 5-10 days depending on the yeast strain.