I recently started filtering most of my homebrews. There is much debate in the homebrewing community about the pros and cons of mechanically removing solids from your brews. For me, having clean, ready-to-drink beer the same day I keg is so much of a plus that I do it for most batches. The added cost is minimal after the initial filter purchase and adding a step to my process in order to save grain-to-glass time is a no-brainer for me.
One of the first areas of concern about the effect filtration has on beer is the stripping of body and mouthfeel. The second is the stripping of hop aroma and reduction of perceived bitterness. In order to test out the effects of filtration, I ran an experiment on the California Common I brewed a few weeks back. Before filtering, as a control, I filled a 12 oz. bottle and added 2 grams of cane sugar and allowed it to sit for ten days to carbonate in the bottle. I filtered the rest of the beer, force carbonated (the same day by rolling the keg under high pressure), and used the Blichmann Beergun to fill a 12 oz. bottle.
After ten days, I chilled down the unfiltered bottle and allowed it to settle for a week in the fridge to clear up. The filtered version was kept cold the entire time (as it would be when serving from my kegerator). Here are the tasting notes on the two bottles:
Appearance: The filtered version is a brilliantly clear copper color. The unfiltered version is a slightly cloudy lighter orange-copper color.
Aroma: Filtered version has a clean sweet malty flavor and an orange marmalade essence that I would say closely resembles East Kent Golding hops even though the recipe used US Northern Brewer hops exclusively. Unfiltered has little malt aroma but the same orange marmalade and citrus nose with a slight hint of apple cider. As the beers warmed up, we all picked up a little mint in the nose and flavor.
Flavor/mouthfeel: Filtered was clean and smooth with a creamy malt finish. Not enough bitterness for the style. Unfiltered was much hoppier (probably due to the hop oils sticking to the yeast cells), sharp, and a bit undercarbonated. I also thought the unfiltered version had that distinct carrot/earth/woodsy flavor that I get from the Cal Common yeast when it’s still young. The unfiltered had a noticeably fuller body and chewier mouthfeel.
Nothing really surprised me about this experiment, but it was nice to have confirmation especially when refining my technique. Even when blind tasting both beers, all three tasters could pick out which was filtered and unfiltered. Both were good beers and it was hard to choose a favorite. The filtered version is obviously more attractive because of the clarity but definitely needed a bump in bittering and aroma hops to be more enjoyable. The unfiltered version would probably get better with time in the bottle as the yeast naturally flocculated out, but the whole reason for filtering is to speed up that maturation by physically removing the yeast. The body and hop issues with filtration can be remedied with recipe tweaks. In the future, I will dial in the mouthfeel of my recipes by bumping mash temps up a degree or two or with using a higher percentage of crystal malts. Filtering definitely affects your homebrew, but paying careful attention to your recipe and understanding those effects will allow you to still hit your target, whether it be style, flavor, or otherwise.