Monday, May 24, 2010

What the HERMS are you doing?? (Part 2 of 2)

In continuing from my last post...

The next step up from single infusions mashes are multiple rest mashes. As I had mentioned in part 1, there are a number of rests (including the starch conversion rest). And each rest does something different. Some of the most common rests are as follows:

Acid Rest - Typically around 95 F. It's purpose is to create a nice fluffy bed of goodness for the enzymes that come in later to convert all of the proteins and starches into food for our sugar-hungry booze-poopers (yeast). You see, these enzymes work best at a certain PH that is slightly acidic (between 5 and 5.7). Some grains used can throw that number out of wack. The acid rests does what it can to reel that number back into the appropriate range.

Protein Rest - Typically between 122 to 131 F. The enzymes active during this range of temperature break down heavy proteins which cut down on haziness and clean out the flavor of a beer (like you would find in lagers). This rest is mostly  used in lagers, because the extra taste complexity from the proteins are desirable in ales.

Starch Conversion - Typically between 149 to 160 F. This is the main rest in the mashing process. This is where the enzymes really kick it into high gear. Enzymes working here convert starches (which there are a lot of, since we've basically made a grain soup) into sugars for those lovable little yeasties. Alcohol, here we come!

All of these steps up to now have been conditioning the water so the enzymes within can go absolutely nuts. Feeding the frenzy, if you will. Next step however is a little more grim.

Mash Out - Heating the mash to 168 puts a stop to all enzyme action. By killing them. A enzyme genocide. So sad. But it does make your mash flow better when you sparge it (basically put it in your boiling pot). Silver lining folks.

There is a big issue here however. With all these temperature changes you need to add heat to your mash. If you recall, our mash tun is a rubbermaid cooler. There's a bunch of different ways to do this, but placing the rubbermaid cooler on an open flame is not one of them (unless you want a pile of toxic, plastic-y, mash). This is where the HERMS comes in.

HERMS stands for Heat Exchange Recirculating Mash System.
My sketch
In my post "Look Out: Science!" I added pictures of my Mash tun and my hot liquor tank. My mash tun is the rubbermaid cooler, and my hot liquor tank is the decommissioned keg (Note: hot liquor tank does not hold liquor. Just hot water. Don't get excited).

The idea is this, mash gets sucked out of the bottom of the tun (through a screen) by a pump, which pumps it to the hot liquor tank. In normal mode, the mash bypasses the tank and heads back to the mash tun, where it gets dropped off on the top of the tank. This ensures the temperature across the mash stays even (hot stuff rises, remember chemistry? You have to keep it mixed).

There's a thermocouple (fancy word for a thermometer) that senses the temp in the mash tun. When I need more heat, I punch the desired heat into my controller box (no, I haven't finished it yet, so you wont find a post on it). This tells my valves to switch, which sends the mash through a coil at the bottom of my hot liquor tank, which is submersed in water. The hot liquor tank is getting heated (stainless steel won't melt... well... nevermind, I digress). This raises the temperature of the mash going through the coil, returns to the mash tun and mixes it with the mash currently in the tun.

When the thermocouple senses the right temperature has been reached, it switches the valves back again and bypasses the hot liquor tank.

This process gets repeated again and again until I'm done with all my rests. After all this is when I start the boil. Needless to say, this process adds a significant amount of  time to the brewing process. But I hear it's worth it.