One of the most important steps for brewing any beer should always be pitching enough healthy yeast. Without enough healthy cells, the yeast can struggle and even decide to quit. If you are brewing anything with a higher-than-normal gravity, or anything that needs to ferment at a cool
44
CHAPTER 1
Pro
of
1
Job: 11659 Title: #223221_Brew Your Own Big Book of Homebrewing (MBI)
Pro
of
1
Job: 11659 Title: #223221_Brew Your Own Big Book of Homebrewing (MBI)
Brew Your Own 001-240_11659.indd 45 1/9/16 15:10
temperature, it’s a good idea to build up a healthy population of yeast a day ahead of pitching with a yeast starter, or at least pitch more liquid or dried yeast than the recipe might call for. For more information about yeast starters, turn to page 42.
If you have experienced a stuck fermentation, depending on where you are in your fermentation (take measurements with your hydrometer), you can try repitching more yeast. If fermentation stops near the beginning or middle of fermentation, you can pitch another full dose of yeast. If the fermentation stops near the end, try pitching a smaller amount of yeast—about a pint of yeast as a starter. You can also try adding yeast nutrient to be sure the yeast is healthy. Another trick is to kräusen the beer by adding some beer that is in the high kräusen stage of fermentation (36 to 48 hours after pitching for most beers). The rule for kräusening is to add 10 percent of the fermenter volume, or 0.1 part kräusen to 1 part beer.
OXYGEN
In addition to temperature constraints, yeast need oxygen. Aerate your wort well before pitching the yeast, which many beginner brewers do by letting the wort splash when transferring it into the fermenter followed by vigorously shaking their fermenter. A more fail-safe method of aeration, however, is to invest in a simple aeration stone setup. For more information about proper aeration, turn to page 41.
Oxygenating with pure oxygen is ideal, but you can also introduce some oxygen for the yeast by shaking the bucket with the lid on.
45
how to homebrew
Pro
of
1
Job: 11659 Title: #223221_Brew Your Own Big Book of Homebrewing (MBI)
Pro
of
1
Job: 11659 Title: #223221_Brew Your Own Big Book of Homebrewing (MBI)
Brew Your Own 001-240_11659.indd 46 1/9/16 15:10
You may have heard of the term fining, but what does it mean? In fact, fining is brewer’s jargon for the process that is more widely known as flocculation. This term is applied to the process where tiny particles suspended in a liquid are caused to form bigger particles that can then settle out of suspension. Often the suspended particles are held so because they carry like surface charge and repel each other. Reduction of this charge by altering pH, such as by addition of calcium ions, results in agglomeration and settling of the particles, in a process known as coagulation (as distinct from flocculation).
If instead a molecule capable of absorbing onto the particles and large enough to join several particles together is added, we have true flocculation. The added molecule, usually a high molecular weight water-soluble polymer, is known as a “flocculant.” Please note the distinction from flocculence, which is the property shown by particles that are flocculant. A variety of flocculants is available, some of them naturally occurring such as carrageenan (Irish moss, used in the kettle to flocculate trub), gelatin, and isinglass (used as finings in beer). There is also a wide range of synthetic flocculants, dominant among which are very high molecular weight polyacrylamides and polyacrylic acid and its derivatives, though these are not used to clarify wort or beer. Note that other polymers used in beer treatment, such as Polyclar and silica gel, are not flocculants—they are insoluble and are used as adsorbents for proteins and tannins that cause chill hazes in beer.
WHAT ARE FININGS?
Finings are substances to assist the removal of suspended yeast from beer, that is, to clarify the beer. Really only two products have been used to any extent in brewing: gelatin and isinglass. They are somewhat similar chemically, in that they are both proteinaceous, which means they can carry either a negative or positive charge according to the conditions of their environment. That is good, for it is these charges that enable the molecules to adsorb onto the surface of yeast particles. They are both quite high in molecular weight (MW)—that is, they are much bigger in size than regular molecules— with isinglass being much higher MW than gelatin.
Both isinglass and gelatin are natural products in the sense that they are processed from natural materials. Gelatin is obtained by hydrolysis of collagen in byproducts from animals, such as bones and skin. It has a wide variety of uses, such as capsules for drugs, a general thickening agent in foods, and, of course, as the principal ingredient of Jell-O. Isinglass is a collagen derived from fish swim bladders, originally those from Russian sturgeons, but now from a variety of other fish from around the world. Its use is largely limited to fining beer, and it has been used as such in Great Britain since the eighteenth century. It has also, of course, been used for fining wines.
Both products are available as purified solids and are quite stable against MW degradation in that form; isinglass may also come in a liquid form as an aqueous solution. Gelatin in fact can be treated fairly roughly, in that it is dissolved in hot (but not boiling) water without