Brewer's Corner - January 2010

Thanks for tuning in for this, the first Brewer’s corner for 2010. I hope your holiday season was as enjoyable as mine.  Last time we talked about malting and mashing and in particular how mash temperature effects beer quality. I’d like to finish out the mashing process by talking about wort separation. At this point we have selected a grain bill that reflects the style of beer we want to make and further have mashed at an appropriate temperature to gain the desired body and sweetness. After a 45 minute to one hour mash rest the diastatic enzymes have simplified the starch chains into either fermentable or dextrin sugars. The important step of separating the grains from the wort is next on the agenda. This is also known as the lauter.

Lauter is a German word which means to cleanse or purify. In essence this is what we are doing here. In some breweries the mash tun and the lauter tun are two separate vessels. Mashing is done in the mash tun and then the whole grist is pumped via a mash pump to the lauter tun. Here at Left Hand we have a combination mash/ lauter tun. This is perhaps the most common approach in small breweries. It is easy to see how the capital expenditure on one vessel is less than two. Plus you don’t need additional floor space for a second vessel for lautering. Why would a brewery want to have separate mash and lauter tuns? Efficiency is the most common reason. We can’t mash in the next batch of beer until the mash/ lauter tun is empty. With separate vessels you can mash in a second brew into the mash tun after the first mash is converted and pumped to a separate lauter tun.  As a result you are converting the starches in batch #2 while concurrently lautering batch #1 to the brew kettle. In larger breweries this helps increase output volume of the brewery without building a larger capacity brewhouse by increasing how many batches can be brewed in a day. Overlapping brewing processes is critical to maximizing output and efficiency. Mash tuns or mash kettles are basically steam jacketed vessels with mixers (motorized paddles) built into them. This allows for step and decoction mashing and assures the even dispersal of thermal energy to the mash. Lauter tuns have false screen bottoms upon which the mash rests and are most commonly capable of single infusion mashing only. 

The first step to lautering is called the vorlauf. This again is a German word referring to the recirculation of wort through the grain bed. As you recall the false screen bottom has the mash bed resting on it. The process of vorlaufing re- circulates the wort from under the mash screen and deposits it back on top. This allows the grain bed to stratify by particle size. The larger husk material settles towards the bottom of the mash bed while the powdery smaller particles are deposited on top. The mash bed becomes a filter for the wort. At first clarity is not very good but after a short period of time the husk material traps the smaller particles and clarity is greatly enhanced.  Once the wort has no visible grain particles the flow is diverted to the brew kettle. The first wort is very strong with a high density of sugar present. Typically about 20%- 25% of the wort volume is now collected to the kettle. It is important to not run all the wort over at this time. This will collapse the grain bed and the permeability of the grain bed will be compromised. There are still plenty of sugars left in the mash bed and it would be downright silly to leave this behind. Before the bed is run dry we begin what is called sparging. This is quite simply the re-introduction of hot water to the top of the grain bed. This is then collected in the kettle and those sugars are extracted. After a period of time, usually about 1 ½- 2 hours the kettle is full to capacity and the wort boiling can begin.

There are a few things to remember regarding lautering that will affect the quality of beer being produced. Clarity of the run- off must be maintained. A cloudy lauter produces a beer easily susceptible to haze formation later down the road. It is also important to not oversparge. Too much extraction is not a good thing. Tannins are extracted from the husk in this context which produces a beer displaying astringent flavor characteristics. Once lautering is complete, we have successfully separated the wort from the mash. The spent grains can now be removed and the next step for the wort is the boil. Alas dear readers this is food for another day. Cheers!