Friday, January 21, 2011

A Primer In Brewing

At an extremely high level, brewing is the process of creating a sugary liquid, balanced for flavor and bitterness, that will eventually be converted into alcohol via fermentation.

Let’s start with creating the sugary liquid.

In order to get this sugary liquid, you need a starch source.  The main starch ingredient in most beers is malted barley.  During the malting process, the grain is submerged in water to begin germination, but before it’s complete, the grain is quickly air dried.  In doing this, enzymes develop on the grains that become the key component for us in converting the starches to sugar (the malting process happens way before we buy the grain).

Once we receive the grain, we make a blend of various types (which we call the grain bill) and run it through a mill so that the husk is broken up and the interior starches are more accessible.  From there, we submerge the grains in warm water for various lengths of time so that the enzymes can go to work and convert the starches to sugar.  This is called the Mash.  Different enzymes on the grain are activated at different temperatures, but the main conversion rest occurs between 140-160 degrees F.  Depending on how well the grains are malted and modified, this conversion takes anywhere from 30 to 90 minutes.  

After the conversion, we collect the sugary liquid, which we call wort, through a process known as lautering.  During the mash, the grains and water are inside the “mash tun” and resting on a perforated steel sheet called the false bottom.  This sheet allows the liquid to drain out while leaving the grains behind.  The liquid is drained into our boil kettle, but given the amount of grain inside the mash tun, there’s still residual sugar that we can collect by rinsing the grain with hot water (typically about 170 degrees F).  This is called sparging.  

When all the grains are rinsed and the wort is collected inside the boil kettle, it’s time to boil.  By boiling the liquid, not only do we sterilize the wort, but we also drive off a number of components that potentially could cause off flavors in the beer later.  At various points during the boil, we also add our hops which, depending on when they’re added, impart bitteness, flavor, and/or aroma characteristics.   Depending on the grains that we use and our intentions of the beer, we typically boil anywhere from 60 minutes to 2 hours.

After the boil, the wort has to be brought down to fermentation temperatures before any yeast can be added.  There are numerous ways in which this can be achieved, but most involve using cold water or glycol which run through pipes or plates that are in contact with the hot wort.  The energy is then transferred from the hot wort to the cold liquid until an equilibrium or desired wort temp is reached.

Once the wort has been brought down to fermentation temperature, it’s transferred into a fermentation vessel and oxygenated.  Without getting too detailed, the oxygen basically acts as a nutrient for the yeast and improves their heath before the fermentation begins.  After oxygenation, the correct amount of yeast is added, or “pitched”,  to the wort.  

During fermentation, the yeast multiply and then consume the sugar to produce alcohol, carbon dioxide, and various flavor components (esters, phenolics, etc.) as bi-products.  Since the flavor developments are highly dependent on the fermentation temperature, the fermentation needs to take place in a temperature controlled environment.

Typically after fermentation completes, which can be anywhere from 4 days to a few months depending on the type of beer, it goes through a conditioning phase.  The beer is typically cooled to around freezing temps which causes the settling of yeast and the coagulation of proteins, both of which add to the clarity of the beer.  Because certain flavor compounds are not soluble at cold temperatures, this conditioning phase also helps to create a cleaner tasting and smoother beer. 

Once the conditioning phase is complete, the beer is ready for carbonation and packaging.  Carbonation occurs one of two ways…either forced or naturally.  With forced carbonation, the beer is placed into some vessel which can withstand high pressures (like a keg) and C02 is pumped in.  The pressure in the vessel causes the C02 to go into solution thereby carbonating the beer.  From here, it can either be dispensed directly from the keg or transferred under pressure into bottles.   In natural carbonation, CO2 is still absorbed into solution due to pressure, but it comes from a different source.  Yeast typically consume all of the available sugars during primary fermentation, but if you add a small amount back into the beer, the living yeast will go to work on it causing another fermentation.  Right after the sugar has been added, the beer is placed into a sealed vessel (either bottles or a keg) and the yeast start eating the sugar.  As a by-product, they also produce C02 which should build up to enough pressure inside the vessel to force it into solution and thereby carbonating the beer.

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