Fining Homebrew
“Finings” is brewer speak for flocculants that are used in brewing to clarify suspensions of solids in a liquid, such as trub in wort and yeast in beer. Such solids remain suspended because they are small so that they can settle only very slowly, and because they usually carry the same charge and so repel each other and prevent aggregation. Flocculants are generally big molecules, usually carrying some charge and soluble in the liquid medium concerned, and are capable of attaching to several suspended particles at the same time, thus making one big particle (floc). Since the settling rate of a particle in a liquid is directly proportional to the square of the particle diameter you can easily see that use of a flocculant can rapidly clarify a suspension that otherwise might remain hazy for days or weeks. There are many types of flocculants out there, including synthetic ones that are very widely used in a variety of industries, but only a limited number of naturally occurring products are used in brewing applications. In the brewery, finings/flocculants are used in two places, namely wort clarification and finished beer clarification, and the type of flocculant used in each of these cases are quite different. I shall deal with the former first.
Fining Wort
It is often held that what we are looking at here is flocculating the trub, trying to make it dense enough to settle out on the bottom of the kettle in a compact mass. If that can be accomplished we can separate the wort from the trub and minimize the amount of wort lost in the trub. In fact this is a misconception, because kettle finings actually work only during cooling. In other words they do not flocculate the hot break (trub), but the material that precipitates as cold break. There is only anecdotal evidence that there is “tightening” of the trub by kettle finings but there is good evidence that their use materially improves the colloidal stability of the beer, thus helping to limit haze formation in the finished product.
The cold break consists mainly of proteins and protein degradation products. So the flocculant used for this purpose must be capable of reacting with these particles. It is worth noting that proteins are based on amino acids, and are what chemists call “amphoteric,” that is to say they possess both basic and acidic properties, and whichever property is dominant will depend upon the pH (acidity) of the medium. In our case the medium is wort, which will be on the acid side (generally less than pH 5.0), and the proteins and protein residue will be mainly positively charged.
The substance that has been found most suited to this is called carrageenan, and not surprisingly it carries a negative charge. It is a linear polysaccharide, linearity generally being a desirable quality in a flocculant molecule. But more importantly it carries a number of sulfate groups, which are of course negatively charged even at wort pH, and so can react directly with the positively charged protein molecules. Carrageenans are unique molecules since sulfate groups are rarely seen in naturally-occurring organic molecules.
Carrageenans are obtained from seaweed, notably Chondrus crispus, which is found off the coast of Ireland. “Carrageenan” is a corruption of an Irish word, and the preparations used for kettle finings are often referred to as Irish moss. Originally, Irish moss was used in the form of the raw seaweed, often in powder form, and was available from homebrew suppliers as such. Later, refined extracts that were more efficient in performance than the raw product were developed. Ultimately, they were refined into tablet or pellet form, containing not only carrageenan but also a dispersant such as sodium bicarbonate and an acid such as citric, so that the tablets would effervesce when added to the wort. For the record, I have used the raw type of Irish moss, but found the results quite variable; in one case its use resulted in formation of a gel in the wort that was very difficult to remove and significant wort loss!
There are three main varieties of this carrageenan, known respectively as kappa, iota, and lambda carrageenan, and it is apparently the kappa form that is most effective as a flocculant. Relatively recently it has been found that a Pacific seaweed, Eucheuma cottonii, contains a higher proportion of kappa carrageenan than does Chondrus crispus, and can be refined to give high activity copper finings. Such products come in the form of a powder or as tablets.
These products come under various names, such as Whirlfloc, Koppakleer, and so on. These are sometimes confusing, with products from the two types of seaweed coming under the same heading. Your supplier should be able to tell you the type of seaweed it is from — don’t be shy about pestering their representatives for the answer if they don’t know! Of course, it can be argued that the exact source does not matter, since they all have the same active ingredient, so they should give equally good results if used according to the manufacturer’s instructions on when to add them to the kettle boil. This is usually 15 minutes or less before the end of the boil so as to give sufficient time for the carrageenan to dissolve. Longer residence times in the boil may result in significant degradation of the carrageenan molecule.
Depending upon the product you will need to add only a small amount. A 5-gallon (19-L) brew would usually require 2–2.5 g powdered Irish moss, or 0.5–1.5 g refined carrageenan. Most homebrewers don’t have the capability to accurately weigh such small amounts, and base additions on the tablet form. Suppliers may also do this, using phrases like “half a tablet per 5 gallons (19 L).” That generally works well in my experience, but you would be well-advised to make it a “small” rather than “large” half. That is because overdosing (with any flocculant) can result in big fluffy flocs that will retain much of the wort, and if you go even further, high dosages can actually result in stabilizing the solid suspension, rather than settling the solids.
Fining Beer
In this case we are talking about separating yeast from beer after fermentation. Such fining treatment may be carried out as a stand-alone process or in conjunction with filtration. Since yeast generally carries negative charge at the pH of beer (about 4.0-4.5) a flocculant that is positively charged is clearly desirable. And as I discussed earlier, proteins have a negative charge at this kind of pH, so that it is not surprising that the two products most widely used are proteinaceous in character, namely gelatin and isinglass. The basic chemistry of these two compounds is somewhat similar in that they are forms of collagen, but isinglass has a much higher molecular weight than gelatin which is a hydrolyzed collagen. Therefore isinglass can form much bigger, faster settling flocs than can gelatin, which makes it best suited to fining unfiltered draft beers.
Gelatin: Gelatin tends to form much smaller flocs that settle quite slowly so that fined beer in keg or bottle may take days or even weeks to clarify. That may not be a problem for the homebrewer and many of you have used it successfully in this way. It can also be used to advantage in aiding filtration, since the small flocs will not blind the filter medium. In that case it is probably best to store the beer for a few days after gelatin addition and before filtration. In either case, best results will be obtained if the fining is carried out with beer that has been racked from the secondary.
You will need to add about 4–8 g (½–1 tsp) per 5 gallons (19 L). Add about 100 mL (½ cup) cold water, stir, then heat to just under boiling, stirring continually until dissolution of the gelatin is complete. Add it to the racked beer, gently agitate it, then bottle or keg the beer. If you are priming the beer for bottling that should be done at the same time as fining.
Isinglass: This is a triple helical molecule and is extracted from the swim bladders of certain fish. It has been used in Britain since the 18th century when it came primarily from Russian sturgeons, but it is now produced from a variety of more common fish. It forms large, fast-settling flocs capable of forming a firm, compact sediment, which makes it an ideal flocculant for cask-conditioned beers, and I recommend its use for that purpose. Note that isinglass has a proven foam stabilizing effect on beer.
Straight isinglass is not easy to use, for it dissolves only slowly in water or beer. Traditional processes involved “cutting” of the shredded product with a mildly acidic liquor (sour beer was a favorite for this!) for several days together with agitation of the liquid. But modern manufacturing techniques have improved the product in various ways so that homebrewing suppliers offer more useful forms, either already dissolved or in a form which dissolves relatively rapidly. In either case you should follow the instructions provided by the supplier — I can’t generalize because of variations in individual products. But as an example, here are the instructions for fining 5 gallons (19 L) of beer with a sample of freeze-dried isinglass: Add ½ level teaspoon (about 1 g) to 1 cup of water, mix with an eggbeater or blender, refrigerate 15 minutes, stir again, then add to beer 3 or 4 days before bottling. Note that solutions of isinglass are usually unstable to heat and will degrade if kept at temperatures above 60–65 °F (16–18 °F), so they are best kept refrigerated unless used immediately.
This is a “one size fits all” approach and ideally the precise dosage should be determined by a series of tests using different dosages of isinglass solution on samples of the beer. Then the dosage that gives both good settling rate and the most compact sediment in a given time is that which will work best for the bulk of the beer. Needless to say, that is not a simple matter for the homebrewer since it requires quite a bit of laboratory equipment and expertise as well as a loss of beer. Generally speaking, 1–1.5 g of dry isinglass per 5 gallons (19 L) will work well enough. However, it does depend upon the yeast itself, and finings should be added at a yeast concentration of around 5 x 106 cells/mL, which means that it should be done after storage in secondary and just before kegging or bottling.
One supplier of isinglass markets it under the name “Biofine” followed by a number. It also offers another product “Biofine Clear,” which may cause some confusion so check carefully with your supplier when ordering either of these. This is a colloidal form of silicic acid in water and has a double effect in that it is designed to not only sediment yeast but also to remove proteins that may otherwise cause chill-haze in the beer. I haven’t yet tried it myself, so I can’t comment further on it. This product is an advance on the “auxiliary fining” concept, where a second fining agent (usually a gum-derived polysaccharide) is added to the beer 24 hours before adding isinglass.
Finale
Whether to fine is a personal choice, and many homebrewers do not find it necessary. After all, in an age when the most popular beer style, IPA, is often so highly hopped that it will always throw a haze when cooled; clear, bright beer is not always as desirable as once was the case. Suffice it to say that I do fine my beers and I always use kettle finings.
