Beer Styles: Lautering strains important beer relationships - part 13

October 16, 9:04 AMBeer ExaminerCharlie Papazian

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Standing on the slotted false bottom this dude volunteers to do the final
spray down cleaning of spent grains in the lauter tun.  Photos by Charlie
Papazian

Lautering is not a word most citizen beer drinkers use on an everyday basis, but it’s one that is on every brewers mind when it comes to brewhouse effort and beer quality.  Lautering is the process of separating the sugar converted (spent) malt grains and cereals from the sweet liquid produced in the mashing process. A “lauter tun” is the vessel in which it happens. 

Lautering, simply put, is the process of straining out grains from the brew liquid.  The methods and care in which a brewer uses to separate and gather the sweet liquid (called “liquor” in the brewhouse) influences the final character of beer. 

Photo right: Going on a brewery tour can be a family affair; it's actually kind of cool to peer down into those mysterious looking vessels, isn't it?

In the brewhouse malted barley is mixed with hot water and soaks for a period of time while enzymes convert starches to fermentable carbohydrates (sugars).  This mash is porridge like and is usually transferred to a lauter tun. Near the bottom of the lauter vessel a “false bottom” is in place.  A “false bottom” is a perforated or slotted strainer situated above the real bottom of the vessel.  The wet, saturated and soupy grain is carefully piled on top of the false bottom.  The process of draining the liquid begins. 

In order to get all the good stuff out of the sweetly saturated grains, brewers sprays hot water (sparge water; sparging) over the grain bed, in effect, rinsing off the sugars subsequently collected through the lauter tun drain and piped over to the brew kettle where it will be boiled with hops. 

If you’re on a brewery tour take a peek into the lauter tun and you’ll notice mechanical devices that carousel above the grain bed.  These are mechanical rakes which can be extended down into the depths of the grain bed as they turn to loosen the mixture. The rinsing sparge water can then flow more easily.

Photo below right: Birds eye view of rakes suspended over newly entered mash.

How does the Lautering effect beer quality?

1. Grain bed depth is a factor:  Too shallow and you get a very fast runoff and carry into the brew a lot of flavor compounds or precursors that can negatively effect flavor, mouth feel, head retention and stability.  Likewise if the bed is too thick it can hold back desired flavor compounds.
2. Lipids are fat/waxy related compounds that are both essential for good fermentation, but if overdone can create problems in some styles of beer.  An elevated level of lipids may be desirable in a beer like oatmeal stout, where they contribute to mouthfeel and body. 
3. Raking the grain bed releases lipids into the flow during the lautering process.  This may or may not be desirable.
4. The level of lipids in the final wort (unfermented beer) will influence ester production.  Esters are the fruity flavors and aromas which are created as the yeast metabolizes sugar into alcohol, carbon dioxide and hundreds of beer flavors and aromas.  Higher levels of lipids can create higher levels of esters.
5. The temperature of the sparge (rinsing) water is an important factor.  Too hot and undesirable compounds are carried through. Too cold and sugar is left behind.
6. The chemistry of the rinse water is a big factor.  Too many minerals or not enough minerals in the water will extract or prohibit extraction of various desired and undesired compounds. 

Next: Beer Styles: Boiling the wort - part 14

Guide to entire 27-part Beer Style Series - table of contents