This document is as accurate as I can reasonably make it but I accept no liability for any of the comments. If you have any comments on the contents, please email me: GraftonG@novell2.bham.ac.uk. Gillian Grafton.
What are Hazes?
Hazes can be subdivided into two main groups, biological and non-biological. Biological hazes are caused by infection of beer with wild yeasts or bacteria resulting from poor hygiene and leading to spoiling of the beer. The haze cannot be corrected. The beer should be discarded and closer attention paid to hygiene for subsequent brews. The haze group of the European Brewery Convention (EBC) defined the non- biological hazes of beer as follows: "The term "chill haze" should be used to describe the haze which is formed when beer is chilled to 0 C and which redissolves when the beer is warmed again to 20 C or more. The term "permanent haze" should be used for the haze which remains in beer at 20 C or more."
Composition of Beer Haze
(i) Physical Composition
Molecules can be broadly categorised as hydrophillic ("water loving") or hydrophobic ("water hating"). Hydrophillic molecules will easily dissolve in water whereas hydrophobic ones will not. If hydrophobic molecules are placed in water they aggregate together to form spherical droplets known as micelles, to minimise their exposure to the water. The resulting suspension of these particles in water is known as a colloid. The presence of a colloid makes the solution appear hazy. This in turn lends itself to the term "colloidal stability" which is the situation in which the solution lacks a haze or a tendency to form a haze. The tendency of micelles to form a colloid is counteracted by alcohol, therefore beers with a higher alcohol content tend in general to have a greater degree of colloidal stability than those with a lower alcohol content.
Hazes are polydisperse, ie they contain a range of different molecules of different molecular weights. The major factor in haze formation is not particle size but the process in which the hydrophillic parts of the molecule (which confer solubility) are blocked by interaction with hydrophobic molecules. The hydrophillic molecules tend to be proteins whilst the hydrophobic molecules tend to be tannins. At first the proteins and tannins interact weakly and form a complex which can easily dissociate into its component parts. This mechanism may account for the formation of chill hazes. These reversible hazes then go on to develop into permanent hazes in which the protein- tannin complex cannot dissociate. This process is thought to involve an oxidation reaction.
(ii) Chemical Composition
The major components of hazes are inorganic molecules such as metal ions; small organic molecules such as oxalic acid; proteins; and polyphenols (tannins). There is no evidence that lipids can contribute to hazes. Rarely starches can form hazes but the usual cause is the use of too high a level of adjuncts such that the starch content cannot be fully converted to smaller fermentable molecules.
(1) Inorganic Components
Iron and copper are the metal ions most involved in the formation of metal-containing hazes. This arises from the contact of the mash and the wort with containers made of iron, copper or bronze. If containers are stainless steel or plastic then hazes due to iron and copper will not usually arise. However it should not be forgotten that soluble iron and copper can be introduced in the water used for mashing and diluting the final wort. Tin, zinc, and aluminium can also give rise to beer hazes, but in practice during homebrewing these do not arise.
(2) Organic Components
Oxalic acid (C2O4H2) can occasionally give rise to hazes known as "green haze", which are usually suspensions of calcium oxalate. Oxalate can arise from malt or by simple oxidation of carbohydrates by micro-organisms. Some brewers recommend addition of calcium sulphate to the wort to a concentration of 250 ppm to eliminate excess oxalate. Usually this is not necessary since calcium oxalate separates from beer during fermentation and storage and is the major constituent (50 to 65%) of the beerstone which forms on the inner surfaces of fermentation and storage tanks in commercial breweries.
(3) Protein Components
It is generally agreed that proteinaceous substances provide the greater part of non-biological hazes, more the 50% of total haze in most cases examined in the EBC haze group report (range 45.5 to 66.8%). Acidic proteins (isoelectric point about pH 5.0) are important in the formation of chill haze and appear to be formed during mashing. The amino acid spectrum of beer hazes closely resembles the amino acid spectrum of barley indicating that all barley proteins are involved in haze formation. Albumens and globulins from barley have been extracted from beer hazes. Studies have shown that proline in haze-forming proteins is important for the combination of these proteins with polyphenols. These particular proteins derive mainly from malt hordein and are largely responsible for chill haze.
(4) Polyphenols (tannins)
Tannins are extracts of various plants which have the ability to react with protein in animal skins to produce leather. Tannins are polyphenols and gradually the term tannin has come to describe all polyphenols in a plant extract regardless of their ability to tan leather.
Tannins are important molecules in brewing and derive from both hops and malt. They have the capacity to react with proteins during wort boiling to form the hot break; during cooling to form the cold break; and post fermentation when they are involved in the formation of chill haze and permanent hazes.
Tannins may conveniently be divided into three classes. The first class is simple phenols which are derivatives of hydroxybenzoic acid or hydroxycinnamic acid. These compounds principally arise from malt but are also present in small amounts in hops. The second class is flavonols which have more complex structures than simple phenols and are principally derived from hops. The third class consists of proanthocyanidins, anthocyanogens and catechins. Anthocyanidins and their derivatives anthocyanins are responsible for the red and blue colours found in plants. This group includes leucoanthocyanins which are known in the brewing world as anthocyanogens and are important in the formation of polyphenols. The presence of these compounds in beer arises from the malt and the hops equally.
All of these single molecules of the various compounds are the building blocks of larger molecules, the polyphenols. The single units are referred to as monomers. Two monomers (not necessarily identical) can join to form a dimer. A dimer plus a monomer form a trimer and so on.
Various studies have shown that monomeric polyphenols have little effect on haze formation but that dimers and trimers strongly accentuate haze formation. Polyphenols on their own contribute little to haze formation. Haze is composed fundamentally of complexes between condensed polyphenols (tannins) and proteins.
There are two similar standards for haze measurement currently in use. Both are based on the use of standard solutions of formazin. The European Brewery Convention (EBC) method uses a range of haze units from 1 to 10 (see table) whilst the American Society of Brewing Chemists (ASBC) method uses a range from 1 to 1,000 (see table):
|Visual Description||ASBC haze units||EBC haze units|
|Star Bright||0 to 34.5||0 to 0.5|
|Bright||34.5 to 69||0.5 to 1.0|
|opalescent||69 to 138||1.0 to 2.0|
|Opalescent||138 to 276||2.0 to 4.0|
|hazy||276 to 552||4.0 to 8.0|
|Very Hazy||greater than 552||greater than 8.0|
For the technically minded standard solutions are made as follows:
(1) dissolve 1 g of hydrazine sulphate in water and dilute to 100 ml.
(2) dissolve 10 g of hexamethylene tetramine in water and dilute to 100 ml.
(3) Mix 25 ml of solution 1 with 25ml of solution 2 and leave to stand for 24 hours. This is the base solution.
(4) A standard solution of 100 EBC haze units is obtained by diluting 1 volume of base solution to 10 volumes with water. Measurements are made at a wavelength of 580 nm.
(1) Dissolve 0.966g of N2H4.H2SO4 in water and dilute to 100 ml.
(2) dissolve 2.417g of hexamethylenetetramine in water and dilute to 25 ml.
(3) Mix 25 ml of solution 1 with 25 ml of solution 2 and leave to stand for 24 hours. This is the base solution.
(4) A standard solution of 1,000 ASBC haze units is obtained by diluting 15 ml of base solution to 100ml with water. Measurements are made at a wavelength of 580 nm.
A direct comparison between the two methods is not exact since haze is not a quantity of substance but an appearance which can vary with the angle of illumination, the colour of the beer, and other factors. However, 1 EBC unit is approximately equivalent to 69 ASBC units.
The amount of haze is measured by passing light through the beer and measuring scattered light at an angle to the direction of the original beam (nephelometry). Scattering is measured against a standard range of solutions of known haze values.
In American breweries the chief instrument used is the Coleman Nephelometer which measures light scattering at 90 degrees. This instrument gives comparable results to those achieved using the Thorne and Beckley Haze Meter which is the chief instrument used in European breweries. Both of these meters measure the haze of beer whilst in the bottle but effects of bottle colour are eliminated by preliminary calibration.
Neither instrument is practical for home use and there is no practical way for the homebrewer to accurately measure haze. The best that can be achieved is to hold a clear glassful of beer to the light, make a rough visual determination and compare this to the haze values listed in the table above.
A wide range of methods have been used on the final beer to predict the ultimate colloidal stability. These have ranged through physical, mechanical, and chemical methods to mathematical models. A comprehensive study using all of these methods concluded that no method of prediction effectively predicts the true colloidal stability of beer.
Factors Affecting Haze Formation
Barley and Malt
The barley committee of the EBC carried out a major trial of 250 barleys over 12 years under varying conditions to identify the variables affecting haze formation. The following factors were found to have a significant effect on haze formation.
(i) Barley Variety
Beers made from varying proportions of huskless malt showed little variation in colloidal stability indicating that substances responsible for beer hazes do not originate from the husk. Large scale trials have showed that beers from 2-row malts had better colloidal stability than those from 6-row malts. Levels of anthocyanogens were found to be higher in 6-row barleys than in 2-row barleys. Place of growth also has an effect with maritime barley malts giving better colloidal stability than continental barley malts.
(ii) Malt Modification
Well modified malts of high proteolytic ability have a greater degree of solubilisation of tannins than less well modified malts. However the tannins are thought to be in a simpler form (more monomers) in well modified malts. In agreement with this studies show that well modified malts tend to form less chill hazes. Blending different types of malt was not helpful, it was found to be better to use one malt of average modification rather than a blend of well and poorly modified malts.
(iii) Protein Content
The effects of the total protein content of barley on hazes is not well understood and differing studies have produced differing results. A number of large trials have found no effect of the protein content of barley on subsequent haze formation, whereas at least one study has shown that lower protein malts give beers with higher colloidal stability.
(iv) Polyphenol Content
Several studies show that the polyphenols present in malt affect colloidal stability more than those of hops. One group developed a barley (ANT-13) which contained low polyphenol levels and showed that this resulted in a beer of high colloidal stability.
The Malting Process
The water used in steeping and during germination of malt can have an indirect effect on the colloidal stability of beer. There is no consensus on the proper composition of the water to be used for steeping, although the use of alkaline water appeared to be beneficial. Similarly there is no consensus on how kilning temperatures affect subsequent colloidal stability.
Milling of Malt
One study has shown that finely ground malts give less stable beers than those from coarsely ground malt and that colloidal instability increases with increasing germination time of the malt. Wet milling was not found to produce differences in colloidal stability compared to dry milling.
The inclusion of maize, rice, sorghum, cassava (manioc, tapioca, mandioca, yucca), wheat starch, triticale or unmalted barley as adjuncts all had no observable effects on the colloidal stability of beer. Malted wheat leads to beer which are less stable than all malt beers, in particular having greater amounts of chill haze. Starch syrups have been used to improve colloidal stability, to achieve the improvement the syrup is fermented separately and added back to the main body of the beer after it has undergone fermentation.
Water (Brewing Liquor)
A major study of the effects of major mineral salts (calcium chloride; calcium sulphate; calcium nitrate; magnesium chloride; magnesium sulphate; sodium chloride; sodium sulphate; sodium nitrate) on colloidal stability showed that, except for calcium chloride and calcium sulphate, the tendency is for colloidal stability to diminish with increasing salt concentration.
The mineral composition of the water affects colloidal stability by the effects of the minerals on malt phosphates. The phosphates present in malt maintain the pH of the mash at a certain value, a process known as buffering. Minerals can affect the buffering capacity of the phosphates either by precipitating them (ie causing them to come out of solution and thus removing them) or by altering the pH so much that they exceed the buffering capacity of the phosphates. In a study of the effects of the mineral composition of water on malt phosphates, one group showed that:
(i) Brews with least mineral additions (no hardness, not alkaline) gave beers with poorest colloidal stability
(ii) Acidifying salts (CaCl2; CaSO4; MgCl2; MgSO4) have a beneficial effect on colloidal stability
(iii) Colloidal stability increases with increased hardness of water corrected with CaCl2.
(iv) Shouldn't brew with demineralised water nor add excess of mineral salts.
CaCl2 and CaSO4 reduce the mash pH. Calcium will precipitate oxalate and proteins responsible for haze. Calcium chloride or sulphate in sparge water lowers pH, the extraction of substances causing beer haze is reduced by low pH.
Iron levels greater than 1 mg/l lead to irreversible colloidal hazes. Iron introduced in brewing water largely eliminated in mashing and boiling.
Copper levels greater than 1 mg/l catalyse autoxidation of polyphenols and give rise to irreversible hazes. A copper content of above 0.1 mg/l can have deleterious effects on colloidal stability. Copper in brewing water behaves like iron in that it is eliminated in mashing and boiling.
A correlation between the anthocyanogen content of hops and the subsequent haze in the beer has been noted. A "haze index" has been defined for hops which is the ratio of polyphenols to alpha acid content. This ranges from 0.15 to 1.71 over the 32 hop varieties determined. Hops (or hop products) with an index less than 0.4 showed good colloidal stability. A study has observed improvement of the colloidal stability of beer as a result of increased alpha acid content of hops.
One study demonstrated clearly that storing hops at high temperatures resulted in beers with poor colloidal stability. The same study also showed that storing hops in a vacuum resulted in beers with a greater degree of colloidal stability.
A number of studies on the effects of hop extracts versus whole hops on colloidal stability have not come to any general agreement. Some studies show that hop extracts improve colloidal stability whilst others show no effects. The only unambiguous finding has been that beers from wort bittered with hop extracts prepared with liquid carbon dioxide have a high degree of colloidal stability, a finding ascribed to the complete lack of tannins in this extract.
Hot water extraction of hops, such as occurs when making a hop tea for dry hopping, leads to the extraction of polyphenols into the hot water. This can have an adverse effect on colloidal stability. When dry hopping with whole hops or hop pellets, this does not occur.
Colloidal stability is affected through the following factors: duration; temperature; mash concentration; pH; dissolved oxygen.
(i) Mashing Conditions
Lower mash pH favours better colloidal stability. 30 minutes, 50 C pH 5.2 to 5.3 favours action of phytases and cellulases. Further acidification of mash (with lactic acid) to pH 4.9 removes beta-globulins. Mashing in at 60 C (as opposed to 50 C) decreased the proteolytic activity of the mash and decreased colloidal stability. Other studies show that mashing in at 50 C led to beers with higher colloidal stability than those produced after mashing in at 40 or 60 C. It was observed that there was an increase in colloidal stability with increases in the duration of the 50 C rest. One study compared mashing at 62.8 C, 65.6 C and 68.3 C and found that the two lowest temperatures gave beers which were more than twice as stable as those from the higher temperature mash.
Beers made from mashes in the complete absence of air were not bright after fermentation, containing a colloidal milkiness which did not settle. Beers from normally oxidised mashes clarified well and those from strongly oxidised mashes clarified very well and rapidly. Two opposing mechanism affect beer haze formation when beers are prepared in oxidising conditions. The amount of high molecular weight proteins is increased so that beer becomes more difficult to stabilise. Opposed to that the amount of proanthocyanidins is markedly decreased.
(ii) Methods of Mashing
Studies showed that a double decoction gave better colloidal stability than a single decoction and that lowest colloidal stabilities were found with infusion mashing. With well modified "ale" and "lager" malts, changes in mashing conditions were found to have little effect.
Beers from mashes in which the husks were not boiled had greater resistance to formation of chill haze than those from mashes in which the husks had been boiled. In another study it was found that very stable beers were produced from malt flour (minus the husks) when hopped with pure resin extracts, and unstable beers were produced when husks or coarse grits were used. Greater colloidal stabilities were found in beers brewed to higher gravities.
Formaldehyde has been used in the mash to remove anthocyanogens (proanthocyanidins). Addition of 1,000 ppm (referred to the malt) of formaldehyde reduced anthocyanogens by 84.8%. This produced a 5 fold increase in colloidal stability. Residual formaldehyde was less than 0.2ppm after use of 350 ppm in mashing.
(iii) Mash Separation
There was increased chill haze when spargings were returned to the wort. A comparison of sparging temperatures of 60, 70, 75 and 80 C showed that the highest sparging temperatures gave the lowest colloidal stability. Increased duration of sparging gave lower colloidal stability. Acidification of the sparge water with lactic acid gave a beer which was more colloidally stable.
Boiling and Cooling
The effect of boiling unhopped wort for 15 to 120 minutes was examined. The chill haze formed in the resulting beer decreased with increasing duration of boil but on the other hand the level of permanent haze increased with boiling time. In a similar study of hopped wort it was found that chill haze increased with wort boiling time up to 60 minutes and then decreased. Permanent haze was unaffected. A separate study also showed increases in colloidal stability with boiling times up to 2 hours.
Highest colloidal stabilities were found with agitated boiling at 100 C with removal of volatiles although the effects were not very large. Non-removal of volatiles gave decreased colloidal stability. The addition of kieselguhr (diatomaceous earth), nylon, or bentonite to boiling wort was effective at improving colloidal stability, with the last two being particularly effective. Addition of activated carbon to the boil had no effect. Irish moss added at 4 to 8 g/hl is also effective at improving colloidal stability.
The rate of cooling of hot wort to pitching temperatures has a profound effect on the amount of cold break (protein precipitate) formed. The ability to chill quickly is a major area of difference between homebrewers and commercial brewers. One study described results in which the best cold break formation was achieved by cooling the wort from 60 C to 21 C in 3 seconds or less. A second study claims that it is necessary to cool slowly over the range 49 C to 26 C to achieve maximum cold break formation and recommends an optimum chilling time of 30 seconds. What can be clearly seen is that homebrewers are at a significant disadvantage in chilling beers when compared to commercial brewers.
Several studies show that cold wort filtered through cold kieselguhr results in very stable beers. In general though, studies show that the raw materials and brewing factors are much more important to the colloidal stability of the beer than the degree of removal of cold break.
Fermentation has a significant effect on colloidal stability although a direct relationship with the finished beer is not easy to establish. Type of yeast, temperature, the shape of the fermenter, and the duration of fermentation all play important roles.
Several authors state that beer of equal quality is produced by conventional fermentation and fermentation in cylindro-conical tanks. In one large study a vertical 10,000 hl cylindro-conical fermenter was compared with conventional fermenters. The cylindro-conical tank gave a uniformly better colloidal stability.
During fermentation there is a loss of proanthocyanidin due to adsorption onto yeast. Yeast appear to act as an insoluble dispersed protein. They absorb tannins more strongly in worts with higher tannin contents. The temperature of fermentation and the concentration of the yeast did not affect this phenomenon. Fermentation temperature can affect the colloidal stability of beer. Several studies show that beers from higher temperature fermentations are more stable than those from lower temperature fermentations. Yeast strain can affect colloidal stability, in general more flocculent yeast produce less stable beers than less flocculent yeasts. The pitching rate also has an effect, increasing the pitching rate tends to improve colloidal stability.
Increased lagering time had striking results in terms of improving colloidal stability. One study recommended that beers should be kept at temperatures between -1 and -1.5 C to assure good colloidal stability. There is of course a risk of freezing the beer so it is useful to know the freezing point of beer. This can be calculated by:
degrees C = -[(0.42 x A) + (0.04 x E) + 0.2]
where A is the weight percent of alcohol (g/100g) (ie ABW) and E is the original gravity of the wort in degrees plato. In general higher storage temperatures give lower colloidal stability.
The use of various additives to stabilise beers is common practice in most large industrial scale breweries. The additives must be recovered from the beer after use to comply with various regulatory body requirements, the usual method for recovery being filtration. Not all of these additives may be legal in all countries - check your local statutes. Beers are treated post-fermentation because substances able to give rise to chill hazes are formed during fermentation, thus treated wort can still give rise to a beer which will develop a haze.
Active carbon is relatively little used to stabilise beer. At high concentrations (50 to 200 g/hl) it can significantly increase colloidal stability.
Beechwood chips (10 to 15 cm long and about 3 cm thick) have been used to accelerate clarification of beer. Chips will accelerate clarification of normal beer but do not ameliorate the behaviour of a beer which normally undergoes poor clarification.
Bentonites [(Si4O10)(Al(OH)2).nH2O] have long been used to stabilise beer. Bentonites are able to adsorb 5 to 6 times their weight of water and the loss of beer is not negligible when bentonites are used. One study shows a loss of 3% with alkali bentonites and of 1% with calcium bentonites. Significant decrease of chill haze is seen when beer is treated with bentonite at the rate of 100g/hl. In laboratory trials the optimum time of contact of bentonite with beer is 1 to 3 hours. On an industrial scale this rises to 1 to 3 days before final filtration.
Silica gels have the formula H2Si2O5. They are used as dry powders which have a high water-adsorbing power. Gels adsorb high molecular weight proteins but the quantities of proteins absorbed were approx. 50% less than those adsorbed by bentonite. Concentrations of 50 to 100 g/hl will stabilise beer. Contact time with beer of as little as 5 minutes is sufficient to stabilise beer but in practice silica gels are added 24 hours before final filtration.
Insoluble polyamide resins can be used to adsorb specifically the anthocyanogens of beer. Treatment of beer with polyamides in the range of 1.0 to 20.0 g/l gives good colloidal stability. A contact time with beer of 24 hours is optimal. One major disadvantage of the use of some polyamide resins is that they can prove difficult to recover from the beer.
Polyvinylpyrrolidine (PVP) can be used to improve the colloidal stability of beer. PVP is a high molecular weight synthetic polymer which is soluble in water. Insoluble forms of PVP (eg Polyclar AT) precipitated more tannins than soluble forms. The use of Polyclar AT at 12 g/hl removed 91 to 93% of proanthocyanidins. The efficiency of Polyclar decreases with increasing amounts of yeasts.
Tannic acids may be added to beer to stabilise it. These tannins are extracts of gall nuts known as gallotannins, gallic or pyrogallic tannins, or tannic acid. Gallotannins bring about the precipitation of complex nitrogenous substances of beer. Oxygen must be carefully excluded when using these compounds to avoid oxidation. If the beer is left in contact with the gallotannins for too long the colloidal stability decreases, therefore it is necessary to filter the beer approximately 24 hours after addition.
Casein, a phosphoprotein isolated from milk, can be used as a stabilising agent. At 200 mg/l casein can improve the colloidal stability of beer. A minimum contact time of 24 hours with the beer is required.
Before the introduction of filters the only products used to clarify beers were fining agents. These were usually isinglass which is an extract of the swim bladders of certain fish. The active element is collagen which coagulates in beer under the influence of alcohol, acidity, tannin, etc, to form a coagulum which precipitates and entrains yeast and therefore clarifies the beer. Collagen is easily converted to a second fining agent, gelatin. Gelatin is an amorphous protein which dissolves in warm water to form a mobile sol or colloidal solution. The temperature of the gelatin solution at addition is 60 to 65 C. Normal addition rates are 1 to 4 g/hl.
Proteolytic enzymes, enzymes which break down proteins, have been used to improve the colloidal stability of beers. The most widely used enzyme is papain. Much research has been carried out on the use of immobilised enzymes on supports such as collagen but this method has not been widely adopted. Soluble proteolytic enzymes are commonly used in conjunction with other stabilisation agents such as PVP or silica gels before the final filtration.
Various anti-oxidants have been used to either remove oxygen from beer or to negate its effects. Ascorbic acid (vitamin C) at 1.5 g/hl reduces the oxidation haze and the effect is similar to that of a marked reduction of dissolved oxygen. Reducing agents containing sulphur can reduce chill hazes. Sodium hyposulphite has some effect on chill haze when used at 20 ppm. Sodium metabisulphite and ascorbic acid (10 to 20 ppm each) have a synergistic action in protecting the activity of papain in beer during and after pasteurisation.
There is a very clear effect of oxygen on beer stability, the greater the amount of oxygen the less stable the beer, therefore care must be taken not to introduce oxygen during bottling. In the USA the head space in bottles fell from 9.2 ml per 12 oz (355 ml) bottle in 1935 to 0.4 ml per 12 oz (355 ml) bottle in 1956. This greatly improved the colloidal stability of the beer. This difference is solely attributable to oxygen. This observation has since been repeated in several purpose designed studies. In an extensive study of British beers the significance of head-space air in bottles was underlined. The optimum head space was less than 1% of the volume of the beer. A similar conclusion was reached in a study of 63 German beers. The temperature of the beer when bottled did not affect the colloidal stability but storage temperature after bottling was important. In general higher storage temperatures led to poorer stabilities.
If you made it through all the technical description you may still be left wondering what you as a homebrewer can do to rid your beer of hazes. Obviously some of the treatments mentioned above are suitable only for large scale industrial brewing, but there are some improvements you can make. If you follow the list below you should be able to produce perfectly clear beers which should be stable for the short time it will take you to drink them.
- Quality of Ingredients.
use the best quality ingredients you can. Don't use malt which has been stored for too long, if it is slack it will result in hazes. Try to use the freshest possible. It may be advantageous to crush your own malt just before you brew with it. Use fresh hops, preferably those which have been vacuumed packaged and stored in the dark below 0 C.
- Get a water analysis.
If your water has high levels of temporary hardness (carbonates greater than 20 ppm) then it will affect mash pH. Boiling the water for 15 to 30 minutes will reduce hardness but make sure that the level of calcium in the water is sufficient to precipitate all the carbonates. If not, add calcium sulphate or calcium chloride to the water before you bring it to a boil. Don't add magnesium salts, these will simply have the effect of solubilising the carbonates. If you want to add magnesium add it after you have precipitated the carbonates. Beware: calcium sulphate can emphasise hop flavour, if you don't want this it would be better to use calcium chloride.
- Check your mash pH.
Aim for pH 5.3, no higher. You can alter mash pH by addition of lactic acid to the brewing water. Remember it is the pH of the mash which matters, not the pH of the water before it enters the mash.
- Protein Rest.
This is a contentious area. Under-modified lager malts should certainly have a protein rest, well modified ale malts shouldn't need a protein rest, but if all else fails you could try it to see if any improvement results. With an under-modified lager malt a rest of 30 minutes at 50 C is recommended. For a well-modified malt some authorities recommend a rest at 40 C for 30 minutes followed by a transition directly to mashing temperatures, specifically excluding staying in the range 45-55 C for any length of time.
- Sparge Carefully.
Don't sparge to too low a gravity. If you sparge much below 1008 to 1010 then you run the risk of extracting tannins which will give the beer an astringent flavour and which will increase the risk of hazes. Don't have your sparge water at too high a temperature. 70 to 75 C is fine, 80 C is too high. Check the pH of the runnings during sparging. If it starts to rise above pH 5.5 stop sparging. Addition of lactic acid to the sparging water can reduce the pH of the runnings, allowing you to sparge for longer.
- Irish Moss.
Use Irish moss in the boil. Many homebrewers omit it because they see no difference, in many cases this is because they use too little. Dr. Fix has shown that scaling down from commercial levels isn't linear. Recommendations vary, but around 5 g per 5 gallon (UK) batch should give good results. Remember to rehydrate it first.
- Have a Good Rolling Boil.
Make sure you have a good rolling boil for at least 1 hour. Don't boil for more than 2 hours since you run the risk of hot break redissolving. Allow the beer to stand for 15 minutes after boiling to allow hot break to settle with the hops.
- Chill Quickly.
Homebrewers can't match the chilling rates achieved by commercial brewers, but they can still improve their beer by chilling as quickly as possible to achieve the maximum cold break formation.
- Bottle Carefully.
When bottling avoid oxidation and try to have a head space in the bottle of less than 1% of the volume of the beer. Be careful though - overfilling can lead to exploding bottles. Once carbonation is over, store your beer in a cool place if it is not going to be drunk quickly.
The Colloidal Stability of Beer by M. Moll in Brewing Science volume 3. Ed. J.R.A. Pollock. Published by Academic Press, London 1987. ISBN 0-12-561003-0. pp 2-329.
Malting and Brewing Science Volume 2: Hopped Wort and Beer by J.S. Hough, D.E. Briggs, R. Stevens, T.W. Young. Published by Chapman and Hall, London. Second edition 1982. ISBN 0-412-16590-2.
Brewing by M.J. Lewis and T.W. Young. Published by Chapman and Hall, London. 1995. ISBN 0-412-26420-X. pp211-218.