What is bottle conditioning? Is it different from simple unfiltered beers?
Throughout most of the modern history of the U.S. brewing industry, a trademark of high quality beer was a crisp, clean and clear beer achieved through high-grade filtration.
Miller Genuine Draft actually advertises that their beer is cold filtered four times.
So the idea of not filtering or actually adding yeast to the bottle may seem strange.
The idea of bottle conditioning has been around for centuries but has only gained a place in the American market since the microbrewery revolution of the 1980s.
Most mainstream brews are conditioned by cold storage where traces amount of yeast that are left over from fermentation complete the conversion and carbonation of the beer.
Filtration then removes any yeast and particles.
In contrast, with bottle conditioning, the final conditioning of the beer actually takes place within the bottle.
Bottle-conditioned beers can simply be left unfiltered or can be primed with a small amount of yeast and sometimes a small amount of sugar in order to give the new yeast something to feed on.
This naturally carbonates the beer in the bottle and gives the beer a long shelf life due to the active aging that is still occurring inside the bottle.
The yeast may also consume any oxygen that is present in the beer, decreasing spoilage.
However, it is often difficult to prevent contamination when bottle conditioning.
Other unwanted bacteria or yeast strains may possibly find their way into the active beer.
In addition, if the yeast does not become active, the beer will not turn out as expected, thus making the consistency between each bottle of beer another complication.
Some brewers suggest that one pours the majority of the beer into a glass, leaving a trace of beer and the yeast at the bottom.
There are then three varying suggestions:
1. Discard the sediment.
2. Gently swirl the remaining sediment and pour into the center of the nearly full glass or...
3. Pour the sediment into a shot glass to be enjoyed separately.
What is an IBU and what does it stand for?
Brewers and beer fanatics use a standard for beer bitterness known as International Bitterness Units (IBUs), essentially a measure of the hop character of the beer.
An IBU is equivalent to one part per million (ppm) of isohumulones,which are alpha acids found in hops.
There are many different varieties of hops, and the method in which they are used can also vary the bitterness.
The later in the brewing process that hops are added, the more of their original character will be present in the final product.
The primary factors affecting IBU scores are the hop variety, method of adding to the brew and of course, the amount of hops used per volume of the actual beer.
Most mainstream domestic brand beers have IBUs close to 10, while the extremely bitter brews that are made for hopheads (who are drinkers that are obsessed with hoppy beers) can approach a ranking of 100 on the IBU scale.
For further information on where many styles range on the IBU scale, visit http://www.beertown.org.
Chris Straub is a senior majoring chemical engineering and a Collegian columnist. He is also the great-great grandson of Straub beer's founder. His e-mail is cts150@psu.edu.
