Adjusting for Filtering
Gravity settling good, filtration bad,” was my conviction for a long while. I joined England’s Campaign for Real Ale (CAMRA) in its early days and am still a member, even though I no longer subscribe to its doctrinaire approach. For CAMRA considers that filtered beer is not “real ale,” because it says that real ale must undergo conditioning through fermentation in its final vessel, that is to say in cask or bottle. If it is chilled and filtered as so many commercial beers are, then it cannot be called real ale. What this implies is that filtration detracts from beer flavor, and, in the context of English commercial brewing in the 1970s and 1980s, chilled and filtered beers were in fact inferior to “naturally conditioned” ales.
But since those days I have tasted many good craft beers that were filtered and I have come to the conclusion that if the recipe is designed on the basis that the beer will be filtered then the end result will be a good, well-flavored beer.
Commercial brewers use filtration to remove the yeast and to give a beer with brilliant clarity, because we do have the bad habit of drinking with our eyes. Of course, BYO readers are more sophisticated than casual drinkers and will carefully consider the flavor, but I can assure you that your perception of flavor will still be influenced by the clarity of the beer to some extent. Many commercial brewers also filter beer, after a period of chilling, in order to remove as much as possible of those materials that result in chill hazes. These are hazes, broadly based on protein/tannin complexes, which form when the beer is cooled from ambient temperature by means of refrigeration. In other words, filtration confers storage stability on the beer. Many craft brewers are less bothered about that because they are often making highly-hopped beers which will throw a chill haze. These brewers do, however, like to filter out the yeast for two reasons, the first being that significant amounts of yeast will give the beer an unpleasant bitter flavor. The second reason for filtering is that getting rid of yeast in the final container means that the beer will be stable to further fermentation. That is particularly important where the beer has been brewed to give a relatively high finishing gravity so that it is a full-bodied drink. I have come across quite a number of beers where a bottle-conditioned version tastes thinner than its draught counterpart because those residual sugars had been fermented out in the bottle.
So now my conviction is, “filtration good, doctrine bad.” Of course, many homebrewers do not filter their beers and use gravity clarification quite happily and successfully. But others like the idea of producing something as bright as any commercial beer, particularly if they want their beer to look its best when it appears before the judges in a competition. That brings me back to what I mentioned earlier and the idea that if you are going to filter, then the beer should be designed in such a way that after filtration it tastes exactly how you want it to taste.
For CAMRA was right in one sense: filtration does remove more than just yeast and chill hazes. It varies according to the efficiency of the filter medium, but filtration can remove color, flavor and head retention of the beer. The standard filters used by homebrewers (and many craft brewers) are called depth filters and are capable of removing particles smaller than the quoted pore size. In other words, a filter rated at 5 microns, about the size of a yeast cell, can remove much smaller molecules, particularly if they are charged, such as proteins and protein degradation products. Some of the latter cause chill hazes as I have said, but others are surface active and help the beer to form and retain a head when poured. There are filter pads available through homebrew suppliers with pore sizes even lower, at around 1 micron, and even 0.5 microns, the latter being “tight” enough to remove even bacteria. For more on the specifics of setting up a home filtration system see Dave Miller’s recent article in the December 2012 issue of BYO.
What I have not seen much information of in the literature is the fact that filtration will take out much of the hop character in the beer. We run a 5-micron sheet filter at BrüRm@BAR (in New Haven, Connecticut) and it is an education to taste the beer before and after filtration. In particular our pale ale, which is heavily dry-hopped in the fermenter, has much more hop character before filtration than after. We could, of course, serve it unfiltered but we do not want to do that for our customers are used to this beer appearing bright. And note that this is a relatively coarse filtration designed to take out mainly yeast and other large particles, such as residual hops. If we used, say, 1-micron filter sheets we would probably remove even more of that lovely hop character.
What are the main problems?
The two effects that homebrewers need to worry about most are loss of mouthfeel (for which proteinaceous materials are at least partly responsible), and loss of hop character and aroma. I would venture to suggest that since these are precisely the aspects of beer flavor that craft and homebrewers want to have more of than you can get in a “standard” commercial beer, then this is a relatively serious downside to filtration.
Solving the problems
The simple answer to reduced mouthfeel, or body, is to increase the amount of malt compared to what you would use for a similar but unfiltered beer. But of course such a remedy is too simple. If you just increase the overall amount of malt you will also increase the original gravity of the beer and its alcohol content. And if it contains highly-roasted malt a simple percentage increase in these can seriously affect the balance of the beer. For example, if you were aiming at brewing a full-bodied stout containing some black malt, and increased the amount of black malt to compensate for filtration, you can very easily make the beer harsh and one-dimensional, and finish up with something like Guinness Extra Stout. In that instance add 10–15% more black malt, but use only the debittered type.
The trick is to increase only those malts which will significantly affect mouthfeel without adding unwanted flavor characteristics. That means opting for one of the many varieties of crystal/caramel malt that are available. For 5 gallons (19 L), try adding around 1⁄2 lb. (0.25 kg) of such malt in the mash, or steeping it if you are using malt extract. This is in addition to any crystal/caramel malt in the original recipe. This means that you are adding about 4 extra gravity points to the beer, which may or may not be significant depending upon the type of beer being brewed. If you think this takes the wort to too high an OG, decrease the amount of pale malt or base malt extract correspondingly.
The choice of which crystal/caramel malt is also up to you, and will vary with the beer style you are making. This is mainly a question of color, as you would not want to add something like Special B or 120 °L English crystal to a pale ale recipe, whereas either might go well in, say, an American brown ale. What you need to do is to think carefully about the style, and then select the “extra” malt so as it will fit in with that style. If you are not sure about the properties of caramel malts check with your retailer, or look at their online catalogues.
Another variation on this technique is to substitute pale malt with some special base malt, such as Munich (again watch the color as it comes in different varieties) or Vienna malt. Check out such malts as I mentioned earlier and don’t hesitate to be creative. A variation you might also want to try with an all-grain beer is simply to increase the mash temperature, say from 150–152 °F (65–67 °C) to 154–156 °F (68–69 °C), in order to increase the amount of dextrin in the beer, which will add to mouthfeel.
Lastly, what about hops? Again this is going to depend very much on the beer to be brewed, but I wouldn’t increase the bittering hops. Overdo the bittering and it will stand out if your filter reduces the mouthfeel of the beer. You do want to increase the amount of late additions for aroma and flavor, however — probably by around 20–50%. And for dry hops added in the secondary fermenter I would go even higher — up to 50%, or even 100% more in an IPA and its variants such as double IPA, black IPA, American stout and so on. This is going to depend on the hop characteristics, and you might even want to change the hop variety for one with a higher level of essential oils. Be careful if you do this latter as you might change the hop character entirely, so you must use hops which will give a similar character. For example Centennial is sometimes known as “Super Cascade,” and is quoted as containing 1.5-2.3% oil. This variety could therefore be used in place of Cascade, quoted at 0.8-1.5% oil, without changing the overall hop character of the beer. (I don’t have space to go into this in any more detail since this is a complicated subject unless you have access to good information and/or a lot of experience with different hops. )
I can’t go into too much detail here on these changes, so I am accompanying this article with a couple of recipes, which you can find on the next page, which exemplify the changes. For simplicity I have chosen a pale ale and a stout so that they have a relatively simple malt or extract bill.
Perfect Pale Ale
(5 gallons/19 L, all-grain)
OG = 1.057 (14.2 °P) FG 1.014 = (3.6 °P)
IBU = 42 SRM = 16 ABV = 5.5%
Ingredients
a) Unfiltered
10 lb. (4.5 kg) 2-row pale malt
1 lb. (0.45 kg) Crystal malt 55 °L
10.4 AAU Centennial hops (90 min.) (1 oz./28g at 10.4% alpha acids)
1 oz. (28g) Mt. Hood hops (0 min.)
1 oz. (28g) Crystal hops (dry-hop) 1.5 oz. (42 g)
1 oz. (28g) US Goldings hops (dry-hop) 1.5 oz. (42 g)
White Labs WLP001 (California Ale) yeast
b) Filtered
9.6 lb. (4.35 kg) 2-row pale malt
1 lb. (0.45 kg) Crystal malt 40 °L
10.4 AAU Centennial hops (90 min.) (1 oz./28g at 10.4% alpha acids)
1 oz. (28g) Mt. Hood hops (0 min.)
1.5 oz. (42 g) Crystal hops (dry-hop)
1.5 oz. (42 g) US Goldings hops (dry-hop)
White Labs WLP001 (California Ale) yeast
Step by Step
The brewing process is identical for both versions of this beer. Mash in the grains with 3.75 gallons (14 L) of water to reach 151–153 °F (66–67 °C) and hold for 60 to 90 minutes. Run off and sparge with hot liquor to collect 5.5–6.0 gallons (21–23 L) of wort. Boil 70 minutes, adding hops as listed above. Run off and cool to around 68 °F (20 °C), then pitch with yeast, preferably as a 1–2 qt. starter. After five to seven days rack to secondary, add Crystal and Goldings hops in a muslin bag and leave for at least two weeks before racking.
Beer a) can then be bottled or kegged, while beer b) will be racked to a keg and filtered, when it can be kegged or bottled.
Not Too Dry Stout
(5 gallons/19 L, extract with grains)
OG = 1.040 (9.8 °P) FG 1.010 = (2.6 °P)
IBU = 30 SRM = 51 ABV = 3.8%
Ingredients
a) Unfiltered
4 lb. (1.8 kg) Amber malt syrup
0.8 lb. (0.36 kg) Amber DME
0.8 lb. (0.36 kg) Belgian special B malt
0.75 lb. (0.34 kg) dehusked black malt
8.1 AAU US Goldings hops (60 min.) (1.8 oz./51 g at 4.5% alpha acids)
1 oz. (28 g) Liberty hops (0 min.)
Wyeast 1084 (Irish Ale) yeast
b) Filtered
4 lb. (4.35 kg) Amber malt syrup
0.6 lb. (0.27 kg) Amber DME
0.5 lb. (0.227 kg) Belgian special B malt
0.75 lb.( 0.34 kg) dehusked black malt
8.1 AAU US Goldings hops (60 min.) (1.8 oz./51 g at 4.5% alpha acids)
2 oz. (56 g) Liberty hops (0 min.)
Wyeast 1084 (Irish Ale) yeast
Step by Step
Steep the grains (in a muslin bag) in 2 qts. (2 L) water at 150–160 °F (65–71 °C) for 20 to 30 minutes. Remove the bag and rinse with 2 qts. (2 L) hot water. Transfer the liquid to the boiler. Carefully dissolve the malt extracts in the wort and top up to 5 gallons (19 L) of water. Bring to a boil, add hops as listed above. Siphon wort from the trub and cool to around 68 °F (20 °C), then pitch with yeast, preferably as a 1–2 qt. starter. Ferment five to seven days, and rack to secondary for a further seven days. Beer a) can be bottled or kegged immediately, while beer b) is filtered before kegging or bottling.
