Dear Mr. Wizard,
Would fining with gelatin have an adverse effect on naturally conditioned beer? I’ve already used Irish moss on my second all-grain batch (2 tsp. to a 5-gallon pot in the last 15 minutes). I racked it to the secondary yesterday and the brew still looks pretty opaque. I’m curious about adding gelatin to the secondary as it is an edible food product; I just fear it would effect the yeast too badly. Would gelatin be okay, or should I steer clear from it? I’ve also looked into Polyclar, but don’t want to use powdered plastic as a fining agent.
The Wiz Responds:
Fining is one of those brewing practices that takes some “touch and feel” to perfect. Not all beers respond equally to finings, regardless of the type. That’s because the components in the beer affected by finings, primarily protein, yeast and polyphenols vary in composition. This is especially true of yeast because different strains vary in flocculation and respond differently to collagen finings (gelatin and isinglass).
Irish moss is used to help remove protein from wort, which ends up in the trub and is separated from the wort prior to fermentation. The next step in the brewing process where finings are used is post fermentation. Cask conditioned ales are racked into a keg where isinglass finings, priming sugar and often times dry hops are added before the keg is sealed up for conditioning. Isinglass is made from the cleaned and dried swim bladders of certain fishes and contains a very pure form of collagen. Gelatin is also rich in collagen, but it is not as pure as isinglass and is not as effective at removing yeast. Both can be used in brewing.
The preparation of isinglass involves stabilizing the protein in an organic acid (tartaric or malic, for example) at a pH of ~2.5. When added to beer isinglass casts a large open net with positive charges on the surface of the molecule. These charged sites act like little magnets and electrostatically bind yeast cells, due to the overall negative charge of yeast. The pH of beer is usually around 4.5 and at this level the collagen begins to precipitate from solution. As the collagen precipitates it falls through beer pulling yeast to the bottom of the fermenter. It is also important that you store and use your finings at a temperature range of 42–55 ºF (6–13 ºC), or they simply will not fine your beer correctly.
Not all yeast respond the same to this method of fining because not all strains have the same density of negative charges on the cell wall. Trial and error will tell you if the yeast strain you use is effectively removed by isinglass. Most serious users of finings perform bench top tests to avoid over fining. A good starting point with isinglass is 1 mL isinglass solution per liter of beer.
Finings remove compounds from beer and wine and the compounds removed are singular. Add too much isinglass and you may end up stripping more than yeast from your beer. The philosophy with fining is to add just enough to accomplish the primary goal. The concentration of yeast after fining with isinglass can be quite low and ales fined with isinglass typically contain less than 100,000 cells per mL, sometimes as low as 10,000 cells per mL. Most commercial breweries that I know who bottle-condition like to see ~one million yeast cells per mL of beer. Anything significantly lower than this density causes problems with carbonation. This takes us back to cask-conditioned ale. These beers carbonate during the same time that the yeast is being pulled down to the bottom with the isinglass. The other key to recognize with fined cask beer is that the cask has a belly where the yeast can collect without flowing to the tap. Since isinglass forms a fluffy yeast layer it is important not to disturb a cask that is being dispensed.
Bottled beer is another animal and you cannot use the cask technique to fine, prime and condition beer in the bottle. The floc would never stay at the bottom of the bottle during those necessary movements (i.e. transfer to the fridge, drinking from the bottle or decanting to a glass). You can fine your beer with isinglass (or gelatin), rack the clear beer off of the yeast and add yeast and sugar to the beer prior to bottling. This allows you to have clear, fined beer and sufficient yeast for carbonation.
Everyone is entitled to opinions and I thought I would offer a counter-point to your aversion to PVPP. Beer comes into contact with all sorts of compounds that are undesirable in the product eventually consumed. Glass, for example, is not something you want in the beer when it comes time to drink it! PVPP is a synthetic fining used to remove tannins from beer and the goal is to reduce chill hazes from forming. Silica gels are used to remove haze-active proteins and some brewers the two finings in conjunction to combat chill haze. These compounds are insoluble and tend to sink quickly. This makes them relatively easy to remove by racking or filtration.