Rock Bottom Breweries are on the vegan watch list because we sometimes use isinglass. Some of our brewers use a product called Alginex before filtering so they don’t have to use as much diatomaceous earth (more on DE later). A well-made and lagered or aged beer will drop “bright,” but many brewpubs don’t have the time or tank space for such luxuries.

Strip it out

Filtration is a mechanical method of clarifying liquids in general and beverages in particular.

Sheet, plate, and frame filters are widely used in the craft beer industry. Sheets are paper embedded with keiselgur or diatomaceous earth (DE), a powdery mineral that is the fossilized remains of diatoms, a variety of marine algae. DE, graded by size and porosity, is used to filter different materials from the beer.

DE is also be used in lenticular, candle, and plate filters of various configurations to remove yeast and proteins from the beer. The downside to using this is disposal. It can be a carcinogenic health hazard if inhaled. It’s also sharp, even at a microscopic level. (You wouldn’t believe what DE looks like under a microscope.)

Another graded earth, perlite, which is volcanic, is also used as a filter aid. Like DE it is porous, but less prickly than DE. Some versions have a flavor all their own which can pass into the beer or wine.

Cross-flow or ultra filters are also gaining use in brewing: cartridges with a cluster of porous spaghetti-looking tubes embedded in them. Turbid beer is pumped through the cartridge and clarified beer passes through the walls of the tubes while the flow keeps the surface from blinding and it is recirculated back into the product tank. The unfiltered beer is continuously pushed through the cartridges until only protein and yeast are left behind. But because filtration can remove desirable flavor compounds from the beer, breweries who can afford to do so have switched to centrifuges.

Glycol in beer?

Glycol as ethyl or propylene is a common anti-freeze and as propylene, is used in the refrigeration systems of many small breweries. Glycol, whose freezing point is lower than water or beer, is employed as a circulating refrigerant to maintain tank jackets at the proper temperature. Attemperating the glycol in the refrigeration system is done via a compressor running Freon through air cooled coils or sometimes ice banks or water towers. Larger breweries tend to use ammonia as their refrigerant of choice.

But that glycol only ends up in the beer if a tank leaks. That’s an engineering problem. As part of our troubleshooting section in brewing school, we studied the example of a beer whose gravity increased after finishing fermentation. Propylene glycol is more concentrated than most wort or beer and tastes sweet. (I’ve gotten a mouthful fixing a refrigeration line and I don’t recommend drinking it, but it is an ingredient in many intimate lubricants.)

There is an ingredient used in making some beers that contains glycol. Grant Johnston was working on making a fruit beer that could be made quickly for the brewpub in Marin, CA. Grant asked a local company, Mane California Brands, which makes natural fruit flavoring, to design a series of concentrated fruit flavors that could be added to his Grundy tanks a gallon at a time. California Brands uses glycol as a carrier for the flavorings since alcohol added in those amounts would be against ATF (now TTB) rules. Personally I prefer using juice concentrate if I am not going to use fresh fruit, but at least one brewery I have worked for still uses natural fruit flavoring.

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Thanks for reading, friends! Namaste.