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Fining and Priming

Page 1

Contents Of This Section
Fining
Biological Haze
Non-Biological Haze
Chill Haze
Haze Stabilisation
Electrostatic Charges
Isoelectric Points
Copper Finings
Irish Moss
Protafloc
Whirlfloc
Auxiliary Finings
Organic Auxiliary Finings
Silicated Auxiliary Finings
Beer Finings
Isinglass Finings
Isinglass Floc
Isinglass Paste
Pre-hydrolysed Isinglass
Isinglass Usage
Gelatine
Chill Haze Prevention
PVPP
Silica Gel
Fining In Practice

 

Fining

Finings are optional additives that accelerate the clarification of beer. They aid the precipitation and the settling out of haze-forming materials. To a commercial brewer a cloudy beer would result in his customers becoming suspicious of the product and indignantly refusing to drink it. For home brewers the aesthetics are not so important as long as the haze is tasteless; some types of haze cannot be tasted. The most obvious cause of haze is yeast in suspension, but excessive protein in the beer is another common cause of haze. It follows then that fining products centre on removing either yeast or protein from the beer. With the possible exception of copper finings, to be discussed later, most fining products are optional and are not absolutely necessary; some home brewers add finings; some do not.

As most haze-forming materials are particles in suspension they will usually settle out unaided under the influence of gravity, given enough time. Stokes' Law tells us that the speed at which these particles settle out is proportional to their size, their mass, the viscosity of the beer, and the gravitational pull of the earth. We cannot do much about the viscosity of our beer, and even less about gravitational pull, except to refrain from brewing on the tops of mountains or in outer space. Fining, then, concentrates on increasing the size and mass of the particles by causing them to stick together (or stick to something else) and coalesce into larger bodies, thereby becoming heavy enough to fall out of suspension quickly. It follows that the main reason for the use of finings is to get a beer into drinkable condition in the fastest possible time.

There are several haze-forming mechanisms, but they fall into two broad categories; biological hazes and non-biological hazes.

Biological Haze

Biological haze can be caused by yeast in suspension or by infection with bacteria (bacteriological haze). Yeast haze is the most obvious form of biological haze. As yeast is in suspension rather than in solution, it will usually drop out of the beer unaided, given enough time, particularly when the pH of the beer passes through the isoelectric point of yeast which will allow the cells to come together and aggregate. Isinglass or gelatine fining, perhaps used in conjunction with auxiliary finings, will speed up the clearing process or deal with troublesome yeast. Biological hazes usually have an offensive taste; bacteriological haze in particular. There is not much that can be done about a bacteriological haze, except tighten up on cleaning and sterilisation next time round - an infected beer is regarded as spoilt and is best discarded.

Non-Biological Haze

Non-biological haze is usually tasteless, but as haze spoils the aesthetics of a beer, most home brewers prefer their beers to not have one. There are a number of things that can cause a non-biological haze, but the most common form is caused by protein in colloidal suspension. Protein is a wide label that encompasses a very large number of different substances. The enzymes necessary during the mash are proteins, for example, but most types of protein are undesirable in the finished beer, except those that contribute to head retention. There are a number of different types of protein, or protein complexes, present in beer. All are derived from the malt, but they are of different sizes, have different molecular weights, and often require different techniques to get rid of them. Generally speaking, protein in solution does not cause a haze as long as it stays in solution. Unfortunately it usually does not. As a beer ages, some types of soluble protein becomes insoluble and then shows as a haze. This type of haze often manifests itself as a chill haze which initially shows itself only when beer is chilled significantly, but in time the haze becomes permanent and is present even at room temperature.

Haze is formed by particles in suspension and these will either clear down naturally under the influence of gravity (given enough time), or will clear using traditional fining methods. Stuff that is in solution we cannot get at directly. Protein in solution does not usually cause a haze, but, as mentioned earlier, it does not always stay in solution and can cause problems weeks later. To ensure a stable beer it is desirable to remove some components that are still in solution at the time of brewing. To do this we usually change soluble stuff into an insoluble form. There are several ways of doing this. Often we encourage the protein to complex with polyphenols naturally present in beer which makes both substances insoluble. Once it is out of solution and into suspension it can then be "got at" by conventional finings or allowed to settle out naturally in some cases.

The most obvious example of making protein insoluble is the wort boil. Before the boil there is a large amount of protein in solution, but a long boil gradually breaks down some of the high molecular weight protein, denatures it, into insoluble stuff, similar to an egg-white cooking. The mechanical action of a vigorous boil forces these small insoluble particles to collide with each other and stick together, forming bigger clumps or flocs that are heavy enough to fall out of solution when the boil is over. However, this in no way denatures all of the soluble protein or gets rid of it all (In fact we never get rid of it all). After the boil there is still plenty of protein left, particularly protein of low molecular weight, and there is also some denatured protein that, although insoluble, has too small a particle size to fall out of suspension all by itself.

As the wort cools, some of the remaining protein in solution reacts and combines with polyphenols that are also present in the wort. This protein-polyphenol combination is only partially soluble, meaning that it has limited solubility, and its solubility is greatly affected by temperature. The lower the temperature the less of this stuff can stay in solution. Cooling the boiled wort forces more of this complexed protein to come out of solution and into colloidal suspension. This is termed cold break. However, the cold break stuff now in suspension can be of small particle size and low molecular weight. Because the particles all carry the same polarity of electrostatic charge, they can be held in suspension by that charge (charges will be discussed later) and can cause a haze. To overcome this, towards the end of the boil we often add copper finings, usually referred to as Irish moss. This has the opposite charge to protein and will either attract the protein to it and form heavier flocs that settle out, or, with perfect dosing, will attract the protein and neutralise the charges on both the protein and the moss. There is then no net charge to hold either in suspension and the stuff will drop out extremely rapidly. Either way we've got rid of some of the troublesome stuff, but not all of it.

Certain types of protein contribute to head retention and are therefore beneficial in beer. The aesthetic quality of the beer (to some people) would be degraded if these proteins were removed. Therefore, copper finings and auxiliary finings, which both deal with protein, are selective when used in appropriate doses, and will take out haze-forming proteins without affecting the beneficial stuff too much.