Recently I've talked alot about malt extracts, both dried powders and syrups. I also briefly explained malt extract in a previous post. At this point it's time to explain the production of malt extracts for two reasons. First, as an extract brewer it's good to know where your ingredients come from and how they are processed. Second, if and when you decide to become an all-grain brewer, you will need to carry out this process yourself!
A quick note on all-grain brewing. In the world of homebrewers, the vast majority never get into all grain brewing. It requires more equipment, time, and knowledge than making extract brews. The vast majority of homebrewers are just fine and dandy with the convenience and quality of their extract brews and happily stay there throughout their homebrewing careers. If and when homebrewers move to all-grain brewing it is most commonly after having several years of brewing experience.
Now just to note, being beer geeks I don't know how long you will spend doing extract brew before progressing to all grain. There are definitely more variables to mess with as an all-grain brewer. However, I highly recommend you spend significant amounts of time doing extract brewing before progressing. Learning the basics of the process and the practice that comes with lots of brews are invaluable.
Ok enough disclaimers and warnings, lets talk mash! Mashing is the process of talking your milled malted barley, adding water and extracting sweet wort. This process is heavily dependent on biochemical mechanisms and is one of the more interesting and critical steps from a biology geek standpoint. We are relying upon two mechanisms, protease and amylase activity. The products of these two reactions, free amino acids and simple carbohydrates, are utilized by our fermenting yeast. Both of these activities are dependent upon enzymatic reactions, and as you may remember from biology class each enzymatic reaction has an optimal temperature. This will be important later.
In the case of protease activity, we are cleaving up all the proteins in the mash grist into smaller peptides, and hopefully free amino acids. The yeast will pick up these peptides and amino acids to utilize them for further cell growth and division (yay, more yeast cells!). The amylase activities will take the complex carbohydrates in the malt and cleave them down to mono, di, and tri saccharides. It also cleaves larger carbohydrate units but our yeast can only metabolize up to trisaccharides, plus if you let the amylases work for long enough they'll pretty much chew everything up. The two amylases we really care about are alpha and beta amylase. (Don't quote me on the next part until I verify it) If I remember correctly alpha amylase cleaves alpha 1-4 linkages and beta amylase cleaves alpha 1-6 linkages. Anyways, unless your a total bio geek all you need to know is that the amylase takes a complex carbohydrate into a simple sugar.
So now you are hopefully thinking. "Ok, so how do I take malt and get sweet wort out in a practical sense". Well, I'm glad you asked. There's several ways of actually carrying out a mash. First to think about is how much water you use. The rule of thumb is 1 quart of water per pound of grain. However, I much prefer 1.15 quarts of water per pound of grain. Second, your grain should be refrigerated after milling, but brought up to room temperature just before you mash. Since the grain will still be colder than the water you'll want to heat your water about 8 degrees Fahrenheit hotter than the desired mash temperature. I have yet to measure the specific heat of malted barley, but it's on my to-do list.
Here comes the important part, and you have a decision to make (or whoever formulated the recipe made the decision for you). There are three types of mashes, infusion, step, and decoction. I'll omit decoction for a later date just to keep it simple. An infusion mash is run at just a single temperature that is optimal for amylase activity around 154F (general amylase activity, not specifically alpha or beta). The proteases don't behave optimally at this temperature, but they will still work at some level. Fortunately for brewers, maltsters do a very good job of modifying their malt (Read: germinating and allowing free amino acid formation) so plenty of free amino acids are already present in the mash. It should be noted that the vast majority of brewers in the world use infusion mashes for their brews! Don't think its simplistic for only being one step! It solves problems, prevents hassle, and makes some of the tastiest beer I've ever had.
The second type is the step mash. In this variant we raise the temperature to a level of optimal enzyme activity, hold it constant for some time, than raise the temperature again. This method allows us to do protein rests (around 122F) and increase amino acid content. We can do a general sacchrification rest around 154F, or we can do rests for each the beta and alpha amylase (not necessary the majority of the time). One major issue with step mashing is that you need to apply heat to your grist to bring it up to temperature plateaus. If your using a gas burner it is possible to burn malt to the bottom of your kettle (this is bad) which will add funky flavors to your beer.
For a first time all grain brewer, I recommend infusion mashing for a while. The typical mash will take 60-90 minutes and you can know its done by dipping your finger in the liquid. It should taste sweet on your tongue. If your anal you can do an iodine test for starch. Get a sample of liquid in a white bowl, add a drop of iodine. If it turns cloudy and blue, keep mashing.
At this point we have a mash grist thats the consistency of oatmeal and the sweet wort is mixed with the grains. We'll have to figure out a way to separate them in my next piece on mashing out and lautering. In that post I'll cover the final steps in how malt extracts are created (it's only one step off from an all grain brew). Until then, have a look at one of the recommended readings for more on mashing. It's a complex subject and I have by no means done it justice in this piece.
Well, wrote more than I expected to today. I think I'll cool it on Friday to make room for Brendan to post his engineering progress. He's itching to post it so I'll cede the floor to him. I'm brewing this weekend. I think it's going to be amber aleish, but it's entirely of my own concoction. If I get one request or more for the recipe I'll go ahead and post it. Otherwise I'll wait until we have a recipe section on the site.
Until next time, take it easy and happy brewing. Perhaps on Fathers day (this sunday) you can raise a homebrew (or microbrew) in a toast?