How green beer becomes mature

mikeb
Posted by
Mike Benson
on 16/06/21

Mike is the sales manager for Wales and the West of England and is located in Wigan.

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“Nothing happening here. Move on, please.” Yeah, right. A room full of tanks. Nothing happening. That’s nothing apart from the science. Which – as you well know – is more than a little something.

While the conditioning area might at first seem the least interesting part of the brewery to visitors, it just takes a bit of imagination to explain the extraordinary chemistry going on here. I say imagination because you need to articulate in terms that can be easily grasped by your audience members, whatever their level of scientific knowledge. Anyway, I go into quite a bit of depth in this blog – more technical info than your average brewery visitor would want, but hopefully of interest to you on how green beer becomes mature!

When you’re learning to brew, one of the first areas of responsibility you’re given is around conditioning. In theory, there’s little that can go wrong, and it’s hard to screw up. In theory.

Experience told me otherwise. All you need is an undetected problem with the dosing pump, and the brew is screwed. That happened in one of my first jobs. The dosing pump [spewed out too much filter powder / stopped feeding filter powder?], the whole filter was compromised without us knowing, and 70 pallets of packaged beer turned cloudy 2 weeks later. Ooops.

Connecting the pipes seems a simple job, but it’s surprising the number of disasters I’ve heard about caused by ‘simply’ not doing it properly. Then there’s the centrifuge. Generally reliable, but not always. And you really can’t afford for it to go wrong.

But my favourite issue – probably because it was my bright idea to use dry hops in the first place – was the shenanigans around a blockage in the tank. Such an effective plug had been formed by the dry hops that the beer refused to drain. And, of course, the problem was more than an arm’s length down. A trip to Argos to buy 5m long rods did eventually did the job. And left us with some useful tools in case of a sewage problem!

What's conditioning and why does it matter?

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At the end of primary fermentation, the beer is ‘green’, and while drinkable, it’s not the finished article.  Conditioning improves the green beer flavour and stability in preparation for filtration or packaging.  Just to confirm, maturation, lagering and ageing are the same as conditioning.

Approaches to conditioning are many and varied. I have seen green beers where only 1 hour of cold maturation was required, right up to beers needing 6 weeks to come into their own. Regardless of timing, and regardless of packaging, conditioning is a significant part of the brewing process – and an example of alchemy at its best use.

There follows a look at the effect conditioning has on:

  • Flavour changes
  • Haze stability
  • Control of bright and cloudy beers

The end of fermentation:

Once terminal gravity is reached, it’s good practice to harvest the yeast.

Active yeast in suspension improves beer flavour. But yeast at the top or bottom of the vessel is no longer adding any benefit – if left too long, it can have a detrimental effect on beer flavour.  If you intend to re-use the yeast, remove it and keep it cold. If not, discard it. The meaty or marmite flavour it can give is sometimes known as yeast bite.

With the nutrition already used up, the yeast in suspension turns its efforts to reducing the level of diacetyl.  Brewers often let the temperature rise at this stage, as this increases the rate at which diacetyl is reduced.

Once happy with diacetyl levels, the beer is cooled.  At temperatures above 30C, the yeast is still active and further flavour development occurs through secondary fermentation.  Dry hopping the beer adjusts the flavour profile (though make sure you know how to remove the sludge from the tank!) and process aids can be added to help with stabilisation and head retention

If the process aids are added while the vessel is being chilled, convection currents will aid the mixing. Adding pure CO2 has the benefit of increasing hop extraction and purging away volatiles.  After 48 hours, all the goodness should have been extracted out of the hops, and the beer can be transferred to a second vessel or racked into casks.

If you’ve used Clear Choice Malt, stabilisation and haze reduction will be significantly aided.

 

What happens during conditioning?

 

Flavour Development:

What actually happens during conditioning to affect flavour development – and what can be done to influence the changes one way or another?

Diacetyl

Diacetyl smells of butterscotch which is generally unwanted in beers. But think Werther’s Original and you can see that for some traditional ales, it adds character.  Personally, I think it works well with Citra heavy beers.  It’s a compound with a low flavour threshold – it can be detected in lager at as low as 70ppb.

The easy version is that diacetyl is made by yeast during fermentation. What actually happens is that yeasts excrete some of the intercellular pools of 𝛼-acetohydroxy acids into the wort and these acids then undergo spontaneous oxidative decarboxylation to form diacetyl and 2,3 pentanedione.

The good news is that later in fermentation, diacetyl and 2,3 pentanedione are metabolised by yeast to form acetoin and 2,3 butanediol which are much less flavour active.

Reducing Diacetyl

Good fermentation ensures there is enough healthy yeast in suspension to efficiently reduce the diacetyl.  Let the temperature increase towards the end of fermentation to help promote rapid reduction.  Depending on the yeast strain, diacetyl can be reduced at temperatures as low as 40C: it just takes longer.

When Is Diacetyl Low Enough?

Diacetyl level can be checked using steam distillation or GC (gas chromatography). But if these methods are out of your reach cost-wise, then simply heat a sample to 70 oC and assess the flavour and aroma.  Heating the sample makes sure all the diacetyl has been formed.  Allowing the beer to warm at the end of fermentation reduces formed diacetyl quickly, but not all the diacetyl may be formed.  This can be a big problem if the beer is pasteurised at packaging: you will suddenly taste it when its too late.  Heating a sample to 70oC makes sure all diacetyl is formed.

Where The Sulphur Comes From And How It’s Controlled

Some sulphur compounds come from the malted and roasted barley, hops and water, but most sulphur dioxide and hydrogen sulphide is produced by yeast during fermentation.

A good vigorous fermentation should drive off sulphur compounds. The natural mixing and release of CO2 purges it from the beer.  Lager yeasts generally produce higher levels of sulphur than ale yeasts and their cooler fermentations are less vigorous. However, the conditioning process mellows these sulphur notes as they are gently stripped out by CO2  during secondary fermentation.

Excessive yeast in maturation will lead to yeast autolysis – and this can bring a whole host of unpleasant sulphur compounds. So, beware.

Acetaldehyde

You know that tart, green apple flavour you sometimes as an off-flavour in beers? That’s the acetaldehyde (CH3CHO) which normally forms in the early to mid-stages of fermentation.  The later stages of a healthy fermentation see the yeast converting almost all of it to ethanol, ridding the beer of those unpleasant flavour notes.  Again, a decent fermentation is essential, as is adequate conditioning time in optimal conditions.

Changing the Beer Flavour

There can be few herbs, spices or juices that some brewer somewhere hasn’t tried adding to a brew. But the most common way to influence beer flavour is still dry hopping.  After all, the different flavours you can achieve from the range of hops on the market is extraordinary.   –

The problem is, herbs, spices and dry hops add solids to the beer causing processing problems.  To aid sedimentation and to maximise the flavour, you should add hops and flavourings when most of the yeast has settled out (below 1.5*106).

 

Sedimentation

 

A major part of conditioning is to separate yeast from beer and the most common way of doing this is by sedimentation.  The factors affecting sedimentation are:

  • Time
  • Temperature
  • Agitation (lack of)
  • Vessel height
  • Particle size

The rate of sedimentation is governed by Stokes’ Law – hang in there, it’s not brewing-talk without an equation!

V = d2p– ρl)g

18µ

  • V = Settling speed
  • d = Particle diameter
  • ρp = particle density
  • ρl = Liquid density
  • µ = Liquid viscosity
  • g = Gravitational constant

So what does that mean?

Quite simply:

  • Larger particles settle quicker
  • Denser particles settle quicker
  • Less dense/viscous liquids settle quicker

How does that help?

It gives the brewer tools to speed up the sedimentation rate:

  • Chilling the beer encourages particles to form
  • Adding finings encourage the particles to form larger units
  • Using a centrifuge increases the gravity.

Chilling

While chilling increases the viscosity of the beer, it encourages the proteins to come out of solution making them easier to remove.

3 Types of Finings for Beer

  1. Auxiliary finings are usually added at the end of fermentation when the beer is being crash-cooled. The convection currents should allow good mixing. Auxiliary finings are negatively charged and flocculate positively-charged proteins and other materials.
  1. Isinglass finings are positively charged and flocculate the negatively charged yeasts and proteins. When used with auxiliary finings, bigger flocs are made, thus increasing sedimentation rate.  It’s important to remember that isinglass and auxiliary should not be added together. Contact your supplier for information on when to add them.
  1. Tank finings are plant or silica/polysaccharide blends and are the vegan option to isinglass. These work well for most beers, but unfortunately not for cask. They don’t continue to promote settling when the casks are moved around, whereas isinglass finings do.

For more information on finings and how to use them check out these links

Gravity

Gravity is a constant – you can’t do anything about it! Well, you can.  And you do.  Every time you pump beer. Centrifuges are just massive pumps that separate solids from liquids using centrifugal forces.  By increasing gravity, a process that could take days, weeks or even months, can be reduced to hours.  There are different kinds of centrifuges designed for many different applications. For beer, the most efficient is disc bowl centrifuge.  The bowl spins at high RPM, creating centrifugal forces that send any solids to the outside.  The separated beer exits the centrifuge and the solids are ejected based on time or turbidity.

Image supplied with thanks to Alfa Leva


While expensive, centrifuges can reduce beer losses and increase capacity.  If you are in the market for a centrifuge there are a few things to take into consideration:

  • Minimal damage to yeast
  • Minimal temperature pick up
  • Minimum oxygen pick up
  • Maximum beer yield
  • Automatic or manual discharge – modern centrifuges use turbidity control on the inlet and outlet to control the flow and discharge rate. 

Unless you are using a centrifuge, the sediment will fall to the base of the tank.  The tanks could have a conical or dish base and could be horizontal or vertical.  All are perfectly acceptable – but will bring different attributes.

The rate of sedimentation is affected by how far the particles have to fall. Because of this, horizontal vessels give faster sedimentation.  On the downside, they have a large footprint and can be difficult to clean – especially if hop debris is present.

Pressure-rated conicals can generally be used as dual-purpose vessels. The cone angle on DPV’s are specially designed for easy yeast removal but hops can make the sediment sticky and difficult to remove.  It’s common for a racking arm to be located above the sediment.

Even if the tank bottoms have been removed, there will still be a build-up of solids on the side of the tank. As you rack, bits can come off and make their way on to the next stage of the process.  Racking arms reduce the likelihood of this happening but do bring some other risks.  They are usually difficult to incorporate into a CIP and need manual cleaning.

If the racking arm passes through a cooling jacket, its integrity can be compromised, potentially causing chemical contamination.  Yes it can happen and it has happened.

On all vessels, it’s good practice to remove the door rubbers for manual cleaning. While they are off, manually clean the door and surrounding areas. Manway doors can be a CIP blindspot, particularly at the top.  The same thing goes for sample taps and carbonation stones.

 

Cask Conditioning

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Cask beer has been around for thousands of years. Before metal, wood was the material of choice and casks were the only way to store or move beer.  In the UK, cask beer has been the driving force for the success of craft brewers.  Casks are filled directly from fermentation or conditioning vessel. They are then left to condition for between 5 and 7 days. Secondary fermentation matures the beer and raises the CO2 level.

In secondary fermentation, the yeast count and residual sugar content of the beer need to be controlled.  The yeast count can be checked using a microscope and should be between 0.5*106 and 1.5*106 cells per ml.  If the yeast count is too low, the secondary fermentation will be inadequate. This means the beer will be flat. If the count is too high, the beer may over-condition causing high pressures and the risk of casks popping. The beer will also be difficult to clarify.

Residual sugar can be controlled by cooling the FV to between 8 and 12oC before the final gravity is reached. At this temperature, the fermentation will slow but the diacetyl will still reduce. Adding priming sugar can also help.

Traditionally, cask beer is served bright. To help achieve this, add isinglass finings to the cask as it’s filled – or just before it’s dispatched.  To make sure the finings rate is correct – helping ensure beer quality and maximising beer yield – do fining trials on the FV or MV.  For advice on this, speak to your finings supplier.

After the conditioning period, stillage a cask and check for taste, carbonation level and clarity.  Checking the PG and calculating the ABV will make sure secondary fermentation is under control.  Keep a cask and do the same at the end of shelf life. That’s as well as checking the unsalable sediment volume.

 

Haze Formation

 

As you lower the temperature during conditioning, you’re encouraging particles to form and creating sediment. All this improves haze stability.  We class a haze caused by bacteria as biological, and a haze caused by anything else as non-biological.

Non-biological hazes can come from:

  • Calcium oxalate – good levels of calcium in the brewhouse will prevent this
  • Starch – from mashing issues or from intentional addition
  • Β-glucans – from poor breakdown during malting and mashing
  • Protein and polyphenol complexes – by far the most common non-biological haze and classed as:
    • Chill haze – re-dissolves when heated
    • Permanent haze – does not re-dissolve when heated
    • Mixture of chill and permanent – partially re-dissolves

Reasons for chill and permanent haze

Chill or permanent haze revolves around the reactions between proteins, polyphenols and oxygen

  1. Simple phenolic compounds oxidise to polyphenols
  2. Loose bonds formed between proteins and polyphenols produce an invisible soluble colloid
  3. Stronger hydrogen bonds form between proteins and polyphenols producing a colloid insoluble at cold temperatures – Chill Haze
  4. Clusters of colloids result in stronger bonds and the colloids are insoluble at warmer temperatures – Permanent Haze

The levels of sensitive proteins and polyphenols in the beer have an impact on stability along with:

  • Oxygen levels – polyphenols easily oxidise and become highly reactive
  • Metal – such as copper and iron link oxidised polyphenols to protein, speeding up the reactions

Preventing Chill and Permanent Haze

  1. Condition the beer cold. Once the flavour modifications have been made, chill the beer to below -1oC for a minimum of 3 days.  This allows proteins to come out of solution so they can be removed by sedimentation or filtration.  Once the temperature goes below zero, yeast is dormant, so it’s important to have the flavour modifications before final cooling
  2.  Don’t allow the beer to warm up during filtration. While it takes time for them to drop out of solution, they are re-dissolved rapidly, meaning they can pass through the filter
  3. Keep oxygen levels to a minimum
  4. Reduce the sensitive protein levels of the beer
  5. Reduce the polyphenol levels in the beer
  6. Don’t allow the beer to be contaminated with liquor or processing aids containing heavy metals.  Leaving a DE filter in re-circ can pass iron from the filter powder into the beer. Not good. Don’t leave the beer recirculating for long periods – and then you’ll avoid any unwanted pick up.

Ways of dealing with sensitive proteins, polyphenols and oxygen 

ProteinPolyphenolsOxygen
Low nitrogen maltPVPP

(polyvinyl poly pyrrolidone)

Slow non-turbulent fill speed
Silica Hydrogel or Xerogels (adsorbent)Malt with no proanthocyanidins (Clear Choice)Bottom fill
Tannic Acid

(precipitates)

Manage last runningPurge vessels and mains with inert gas or deaerated liquor
Degradation Enzymes (Papain) Manage PAA

The traditional way to stabilise beer is to treat it with silica hydrogel and PVPP.  While silica gel is cheap and effective, PVPP is around £30 per kg and can be difficult to handle. Some grades can be regenerated but this requires a large capital spend and a second filter.

A simple way to avoid the use of PVPP is to use Clear ChoiceMalt.

Generally 70 to 80% of the reactive polyphenols come from the malt – with proanthocyanidins being the most reactive.  Proanthocyanidins belong to a flavonoid group of polyphenols located in the testa of all traditional barley varieties.  Clear Choice – which is GM-free in case you were wondering! – has been specifically developed to be proanthocyanidin-free, removing the need for costly PVPP.

Using Clear Choice:

  1. It works in normal brewhouse operations
  2. There’s no need to add other processing aids
  3. You won’t have any dosing issues
    1. Homogeneous mixing
    2. DO2 pick up
  4. Works brilliantly for cask beer as well as for other formats
  5. Even using as a small proportion of the grist delivers benefits.

 

 

Beer Filtration

 

The fundamental job of filtration is to make the beer bright for its intended shelf life.   To do that, you need to:

  • Remove micro-organisms
  • Remove suspended proteins and other organic debris
  • Clarify and stabilise the beer so its appearance doesn’t alter over time.

So that’s easy, right? You just run it through a filter?

Not quite. There are many different kinds of filters for different applications. For example, you can’t run hazy beer straight through a sterile filter: it will blind or block very fast, costing you a lot of time and money.

Filters are either SURFACE or DEPTH.

Surface filters have a fixed pore size. Particles bigger than the hole can’t pass through it: they get stuck and block the hole.  Membrane filters such as Reverse Osmosis and sterile membrane cartridge filters are an example of surface filtration.  Surface filters block easily when hit with heavy solids so it’s important to keep a close eye on them and regenerate (backflush or CIP) before the filter blinds.

Depth filtration uses very porous, inert powder with massive surface area to form a filter bed.  The beer flows through the powder and the solids get trapped in the holes.  It is possible to use a filter powder that has an electrostatic charge. This charge attracts suspended matter, making the whole thing very efficient.  Powder and sheet filters are good examples of depth filtration. They are capable of coping better with heavy solid loading – and have a higher throughput.

Powder Filters

Powder filters come in many forms:

  • Plate and frame
  • Candle
  • Horizontal leaf
  • Vertical screen

They use diatomaceous earth or kieselguhr as the filter aid.  These are natural products consisting of the fossilised skeleton of microscopic algae that comes in grades from 10 to 200µm allowing for the layering of the filter bed.

The first thing needed on a powder filter is a support sheet. Depending on the filter, it will be a sheet, candle or screen.  You fill the filter with beer, eliminating any oxygen and recirculate the beer.  Before filtering, add the filter bed. Do this in 2 parts:

  • 1st Pre-coat
    • The 1st pre-coat powder is mixed with beer or DAL in the mixing pot. As the beer is re-circulated around the filter at high velocity, the pre-coat is dosed into the beer flow at a high rate.
    • The 1st pre-coat is usually a coarse powder that covers the support medium. Without it, finer powders could pass through the support medium, making filtration inefficient.
    • To ensure good coverage the 1st pre-coat should be applied within a 10 minute timeframe.
  • 2nd Pre-coat
    • The 2nd Pre-coat is mixed and dosed as per the 1st pre-coat
    • A finer powder than the 1st pre-coat, it is common to be the same grade as the body feed, but can often be tighter – to act as a guard.
  • Body feed
    • When the 2nd pre-coat is applied, the body feed is mixed
    • The beer flow is reduced and the powder dosing reduced. Getting the correct rate of body feed is key to effective filtration – and it can be a fine art.
    • Again, the body feed rate depends on the beer solids and flow. For beer with heavy solid loading, the beer flow rate can be reduced and the powder addition rate increased. This is done by extending the pump stroke length or mixing a more concentrated solution.
    • During filtration, keep a keen eye on the pressure differential and adjust the powder dosing and flowrate as needed.
    • The capacity of the filter is based on how much powder it can hold. Beer with low solids need less body feed, giving long trouble free filter runs.  Beers with heavy solid loading don’t, they can be a pain.
    • Overdosing powder can damage the support plates so take care and keep a record of pressures and powder addition.
  • At the end of filtration, the filter housing is opened. All the powder will have built up on the filter support sheet and needs to be removed (dropping the filter).  It can be collected as solid waste. Allowing it to go down the drain is environmentally unsound, can be costly and can land you in trouble with the water company.
  • Dose rates and powder grades depend on filter size and on the solid that’s loading the beer, so do ask for support from the supplier.
  • Depending on the powder grade, particles above 0.5µ will be removed.
  • Mixing filter powders and dropping the filter is a messy job and the powders are potentially carcinogenic. So be absolutely sure to use masks and other PPE.

Sheet Filters

Sheet filters utilise sheets impregnated with kieselguhr to give different grades.  They can also be impregnated with silica gel or PVPP to aid stabilisation.  Like DE filters they come in different forms:

  • Plate and frame
  • Lenticular
  • Cartridge

In use, the operator can only adjust the beer flow rate. This means sheet filters are not as adaptable to higher solid loading as DE filters- but they are much cleaner and can be regenerated by backflushing.

Membrane Filtration

Membrane filters trap particles by virtue of their constant pore size.  They are commonly used in sterile filtration applications and more recently in cross-flow filtration.

Sterile filtration removes all microorganisms that can grow in beer.  They have a maximum 0.45µ pore size and are graded as ‘nominal’ or ‘absolute’.  They are located just before the packaging line and act as guards or policing filters – to ensure no contamination passes into package.  The difference is down to an algorithm, cost and fitting types. For sterile filtration, ‘absolute’ should be used.

Double, open-ended (DOE) filters fit into the housing by compression. Both ends of the cartridge filter are open: they slot into the housing.  While good for some applications, they are not great for sterile filter applications as the seal can allow material to pass.

Code 7 filters have a point at one end and lug fittings at the bottom with a double seal.  The lugs fit into the housing and are twisted to lock them in place.  The double seal ensures no material can pass, making code 7 filters the common choice.

As with the DE and sheet filters, the inlet pressure should be monitored throughout the operation. When the differential pressure reaches the level recommended by the supplier, it should be regenerated.  Again, it’s important to follow the manufacturer’s guidelines as some detergents and elevated temperatures for extended times can damage the filters.  While some can be back-washed, some don’t have an internal structure designed for the backward pressure – so again, check.

Cleaning cycles can damage the filters and general use can cause wear and compromise effectiveness and integrity.  If you have a damaged filter, it becomes completely ineffective and any contaminated beer will pass through.  What’s more, you won’t know you have an issue until it’s too late.

Integrity testing verifies the filter operation and the most common method is the bubble point.  The liquid is held in the pores of the filter by surface tension and capillary forces. The minimum pressure required to force the liquid out of the pores is a measure of the pore diameter.  The information needed is usually found on the filter certificate of conformity or datasheet. Your supplier should be able to help.  Good practice is to check the filter integrity before and after use. You then have peace of mind that the filters are good to use – and haven’t suffered any damage during the run.

Crossflow filtration is not a new technology but it is now an affordable option for craft breweries.  Cross flows were originally found only in very large breweries with centrifuges that ensured the beer was polished before filtration.  Recently, technology has filtered down and smaller units are available for craft brewing.

Usually skid-mounted, cross flows are fully automatic and work by pumping beer across the membrane at high pressure.  The pores in the membrane stop particles passing so they quickly create a block. However, as the beer is pumped across the membrane it sweeps the solids away, reopening the bed – it is self-cleaning!  Eventually the unfiltered beer becomes concentrated, the solids build up and the bed is blinded.  At this point the filter will automatically enter a regeneration cycle. When complete, it will begin filtration.

 

Haze Management

 

Controlling haze is key!  You may think this is important only for beers that are intended to be served bright, but even in a cloudy beer the haze needs to be consistent.

How do we control bright beer haze?

The easiest way is by visual assessment.  Decant the beer into a clean glass and assess its appearance in front of a light.  It can be compared to other beers or you can assess it against an object such as a line.  The downside to this kind of assessment is its subjectivity – you may make a different judgment from one day to the next, and others doing the checks may have different opinions.

Haze meters measure the haze and give a number, so a specification is easy to set.  The measurement is based on the quantity of light scattered by the presence of suspended particles – haze!  The light beam is at 90o or 13o.

  • 90o detects particles <0.4µm that are invisible to the human eye
  • 13o detects particles >0.4µm that are visible

Most beer specifications refer to EBC or ASBC. Both are measured at 90o.  For a bright beer, a measurement of below 0.7EBC would be acceptable and for a cask beer, below 1.5EBC.

Assessing the beer at packaging lets us know the beer is bright at that time but it does not tell us what will happen as the beer ages.  A beer can be crystal clear with a very low haze when packaged, but if not stabilised correctly, the haze will rapidly start to rise.

The quickest way to assess shelf life stability is to use a ‘Chapon’ test.  For this, we add ethanol to the sample before chilling in a water bath @ -8oC for 40 minutes.  Achieving such a low-temperature water bath is challenging but it’s worth it. The test gives a rapid prediction of chill haze and can be done before a packaging run.

Hot forcing and hot/cold cycling give a very good indication of shelf-life stability in the final pack. They are great for small pack but using them for large pack could prove somewhat difficult.  There are many different variations, but they all include a warm forcing stage to speed up any ageing reactions.

  • Forcings – The beer is held at 37oC and once the haze begins to rise rapidly, you can work out the shelf life. 1 week before the haze begins to rise rapidly and you should be able to assume 1 month’s shelf-life at normal storage. 12 weeks before the haze rise, and you have 12 months’ shelf life. If you have a warm room – a boiler room maybe – it is possible to try this with kegs.  Small pack beers are usually stored in an incubator or water bath, and the beer sampled weekly.
  • Hot-cold cycling speeds up the process. There are variations on times and temperatures, but a hot storage period is followed by a cold storage period.  The change in temperature encourages the chill haze to form – and this becomes a permanent haze.
    • 2 days at 60oC and 1 day at -2oC is equivalent to 6 weeks’ normal storage
    • 24 hours at 30oC and 24 hours at 0oC is equivalent to 1 month’s normal storage
  • Using hot/cold cycling can speed up the test time. To replicate 12 months’ shelf life, the forcing test can take 12 weeks. Hot-cold cycling can reduce this to 4 weeks, allowing you to act on the results and make more timely improvements.
  • To warm the sample, an incubator or warm bath can be used and to cool the bath a fridge or cold water bath. Using water baths give a quicker heat distribution and will give different results to air heating.

The table below uses real-life data to show how haze prediction works.

 Control MaltClear Choice Malt Ⓡ
Maturation Temperature+4oC-1oC+4oC-1oC
Initial Haze0.40.40.70.7
Total haze 5 days at 60oC>127.91.21.2
Total haze 60 days at 20oC3.51.60.80.9

We can take a few points from the table

  • The difference in the initial haze between Clear Choice malt and the control malt would wrongly suggest the control is brighter.
  • There is no difference between initial haze when the beer is conditioned at different temperatures.
  • After just 5 days at 60oC we can see the control beer has a limited shelf life, while Clear Choice is shelf-stable even at elevated maturation temperatures.
  • After 60 days at 200C:
    • The control matured at 40C will have a visible haze that casts a sediment
    • The control matured at -10C will have a haze that is visible
    • Both Clear Choice beers are still visibly bright.

While the information does not save the batch, it does allow the brewer to make rapid changes to the stabilisation regime to minimise the issue.

Deliberately creating a hazy beer

Keeping hazy beer consistent is tricky, but the forced haze methods above can still be used to predict shelf-life stability.  While you don’t need to worry about the filter, there are other parts of the process that need to be looked at.

In general, haze in beer should not come from yeast: it should come from proteins.  Over time, yeast can reduce protein and make the beer bright.  To increase the protein content, you can adjust the grist by using adjuncts such as wheat.

It’s also good to use a mixture of malted and torrefied products as they have different molecule sizes.  Try experimenting with wort re-circulation in the mash tun or lauter tun, allowing more turbid wort to enter the kettle.

When boiling, it’s still important to get a good boil and evaporation.  Kettle finings promote the sedimentation of finer proteins and polyphenols, so don’t add them for cloudy beers.

At the end of fermentation, allow the yeast count to reduce before dry hopping.  The use of finings strips out proteins, so you need to rely on time and temperature – unless you have a centrifuge!  You can measure the yeast count using a microscope and you can measure the total solid count using a benchtop centrifuge. Both will give you a number to help set specifications and targets.

There is some research to show the haze potential from dry hopping is affected by pH, with the optimum range of the beer being 3.8-4.3.  Dry hopping raises the pH so extra liquor treatment may be needed to combat this.

 

Good beers are all conditional

 

Nope, the brewing job’s not finished once fermentation is done. Yep, it might look like there’s nothing happening in this next stage, but good beers are conditional on effective conditioning.  It’s fundamental to the quality of the beer – and how it’s presented to the drinker.

The flavour changes occurring during maturation dictate whether beers are palatable and saleable. The storage conditions and filtration regimes then dictate whether they reach their shelf life potential.

While your malt supplier may be the last people you think to call about any downstream issues, malt quality plays a massive part. The technical team at Crisp have vast knowledge in this area. I have produced my fair share of unpalatable, unsaleable and unstable beers – and have a lot of learnings to pass on!

Don’t leave anything to chance. Make use of technical support from your suppliers. Charles Faram and AB Vickers for example, can also help with issues around hopping and stability.  And your filter supplier will be able to give advice about maximising filter performance.

If you have any questions, please feel free to contact us and our technical team will be more than happy to assist.

Beer Glasses Illustration

 
mikeb
Posted by
Mike Benson
on 16/06/21

Mike is the sales manager for Wales and the West of England and is located in Wigan.

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