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Dry yeast rehydration, it’s critical!

By Moritz Kallmeyer
Master Brewer Drayman’s Brewery & Distillery, Silverton Pretoria, March 2005

Each brand of ADY (active dry yeast) specify its own optimum rehydration temperature, ranging from 35°C to 40°C. As you drop the strike temp from 40°C to 15°C the yeast will leach out progressively more of its insides, damaging each cell. The yeast viability thus drops proportionally. At 40°C there is 100% recovery of the viable dry yeast while at 15°C there can be as much as 60% dead cells. The dried yeast cell wall is very fragile and it is essentially in the first minute, even seconds of rehydration that warm temperature is critical while it is reconstituting its cell wall structure. During these first initial minutes of rehydration, the yeast cell wall can not differentiate what passes through the wall. Materials which is toxic to the yeast at this stage like sugars, hop products and SO2 that the yeast normally can selectively prevent from passing through its cell wall, rush right in and seriously damage the cells. The moment the cell wall is properly reconstituted the yeast can regulate what goes in and out of the cell. This is why the suppliers warn against rehydration in wort, instead of water.

The water should be normal tap water ideally with 250-500ppm hardness present. The hardness is essential for a good recovery. This is the reason why distilled or de-ionized water should never be used. I further prefer the water to be carbon filtered to remove any chlorine and impurities, then boiled to sterilize and force chilled down to the required rehydration temperature. Ideally if you have access to it, the warm rehydration water should contain 0.5-1.0% yeast extract like Go-ferm from Lallamand.

Active dry yeast is dormant or inactive, not inert, so it should be kept refrigerated at all times at around 4°C. It will only loose 4% of its activity in a year if kept at this temperature. Remember to remove the package from the refrigerator early on brew day so it can naturally attemperate to the rehydration temperature. This prevents one stressor, temperature shock. I prefer to do the rehydration process in a hygienic polyethylene bucket. The yeast should be sprinkled into 10 times its own weight of rehydration water and gently folded in with a spoon to wet them. Oxygen is not needed at this stage so stirring should be avoided. After sitting for the recommended 15 minutes give it a vigorous whirl then again close the lid of the bucket lightly and leave it for 5 more minutes at the specified rehydration temperature. Built into each cell by the manufacturer is a large amount of glycogen and trehalose reserves that give the yeast a burst of energy to kick off the growth cycle when it is added to the wort. It is quickly metabolized and used up by the yeast within about 30 minutes of rehydration. There is no damage done to the yeast if it is not added to the main batch of wort within this period of time – you just do not get the benefit of that sudden burst of energy and lag times are likely to increase. The rehydrated yeast, being warm, should now be cooled to within 4°C of the wort before pitching. This attemperation is done over a brief period by adding in increments, a small amount of cold wort (removed earlier from the kettle and chilled) to the rehydrated yeast container. Rehydrated warm yeast pitched into cold wort will cause many of the yeast cells to produce petite mutants that will never grow or ferment properly and will cause them to produce H2S.

Some ADY manufacturers recommend slightly lower than normal wort aeration while others argue that most ADY yeast actually require no O2 addition for successful, average gravity wort fermentation. There are enough lipids built into the cell at the yeast factory. It will however need O2 addition on the next re-pitching.

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To mash or not to mash Kurz / Hoch
By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton Pretoria, October 2004

Introduction

The Kurz /Hoch method of mashing was recently advocated when both studies at Weihenstephan State University and reports by Michael J. Lewis and Tom W. Young (Brewing, Second edition, p.244) confirmed the following: wort dextrins have no flavour of their own and are not viscous enough in solution to account for the perceived (sensory) viscosity or “body” of beer. Something else (the subject of current research) contributes to the perception of “body” in beer, not dextrins. It is thus assumed that traditional complex mashing regimes which were done to promote dextrin formation in order to promote “body” are redundant. The main question to ask if you are considering mashing Kurz/ Hoch is: “What malt am I going to use?” The Kurz /Hoch mashing method is not suitable for cereal adjunct inclusions.

1. Mash short

With the great excess of enzymes in modern malt, conversion can be achieved a lot faster than once believed (remember almost all fully modified malts are designed for big brewers with high cereal adjunct rates). The less time spent mashing the better. 20 Minutes maximum at conversion temperature. The underlying principal is to create maximum extraction with minimum grain contact time.

2. Mash high

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Yeast slurry pH as an indicator of yeast Autolysis

By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton Pretoria, January 2004

At the end of fermentation, beer pH is usually between 4.1 and 4.40. An increase in stored yeast slurry pH above this end of ferment beer pH is a good indicator of yeast autolysis. Protease’s and other low molecular weight compounds of an acidic nature are also released which causes an initial sharp drop in pH during the first 24 hours of storage at 4°C. However, when a slurry is monitored right from the end of harvest through to re-pitching, there is a gradual increase in pH – especially from day three onwards.

Other compounds in the stored slurry that impacts negatively on subsequent fermentations are:

1. An increase in FAN (free amino nitrogen) especially from day three onwards;
2. A decrease in the stored glycogen *content (time and temperature dependant);
3. An increase in the trehalose *content which is indicative of a response to increasing stress.

The authors concluded that the measurement of slurry pH is a simple, quick and inexpensive method to determine the quality of yeast slurry. The use of slurries showing high pH values impacts negatively on beer foam and beer flavour of the beer produced.

• Trehalose (a non-reducing disaccharide / carbohydrate) is primarily a stress protectant at the cell membrane for organisms like yeast because it pocesses the ability to act like water (particularly during dehydration) as a water replacement.
• Yeast will accumulate trehalose earlier during its growth when the major sugar in the wort is maltose
• It appears to play an energy reserve roll (as a storage carbohydrate) in cell sporulation.
• In brewing the stress of high gravity, osmotic stress, high temperatures, low levels of water activity and ethanol toxicity all induce synthesis of trehalose.
• Threhalose is normally accumulated later in the growth of yeast than glycogen, at the decelerating phase.
• Normal percentages in a cell is 1-2% of the dry weight, 5-10% is a little uncomfortable but higher than 10% is unacceptable except in dry yeast as this is essential in allowing the dehydration to occur successfully.
• Some reports say that a high trehalose concentration in yeast at pitching improves viability, enhance the carbohydrate utilization rate and increase the production of higher alcohols such as isoamyl and isobutanol.
• Glycogen is a storage carbohydrate essential in the lag phase for sterol synthesis, which is essential for good brewing yeast and thus a healthy fermentation.
• Glycogen is accumulated in yeast early, while the glucose / sugar content is still high – it levels off as the yeast enters the stationary phase.
• Glycogen degradation is accelerated when yeast is exposed to air during yeast handling or disturbed excessively between brews – with resulting poor yeast performance.

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The do’s and don’ts of yeast handling
By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton, Pretoria, November 2003

The aim of this article is to discuss improved methods of yeast handling in a brewery to ensure good yeast health and optimum fermentation performance.

Introduction

The reality in most craftbreweries is that brewers don’t handle their yeast correctly ultimately impacting negatively on beer flavour. Conventional methods by old timers rarely involved much more than collecting yeast from a previous batch and unceremoniously dumping it into a new batch.

Yeast Handling

1. The first step in ensuring that the next batch of yeast collected will be of good health is: daily trub removal from the fermentation vessel (FV).
2. As soon as the yeast has dropped out of suspension (before chillback) The yeast must be warm cropped. Early warm cropping has significant benefits on yeast vitality.
3. Yeast to be stored must be chilled down immediately to 0-2ºC. The thin early crop contains enough beer that will form a hydrative layer on top of the yeast in the storage vessel. No CO² pressure build up is allowed – due to the risk of CO² poisoning.
4. Collected yeast should not be cold stored (before repitching) for longer than three days(optimum) or seven days (worst case scenario)
5. Removing a batch of yeast from cold storage , critical inspection of the yeast, and timely acid washing of the yeast are some of the first routines on a brewing day. Principals of acid washing includes beer layer removal, dilution with sterile acidified water, pH lowering to 2.1-2.2; straining to remove protein trub; sedimentation to remove dead cells and regular uniform mixing.
6. After a period of settling (+/- 3 hours) the excess acid water forming a layer on top of the yeast is removed and the yeast roused with fresh sterile wort from the kettle (5% of yeast volume) and sterile cold water.
7. After rousing, the yeast is allowed to gradually atemperate to close to pitching temperature to avoid any temperature shock.
8. One of the guiding principles in yeast handling prior to pitching is the adequate mixing of yeast until a uniform, decarbonated suspension has developed.

Summary

The key words in yeast handling are keep it cold (KIC), keep it short (KIS), keep it simple (KIS)

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Tasting of beer
By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton Pretoria, March 2003

Introduction:

After an exercise session your brain secretes endorphins – a powerful hormone like chemical that leaves you with a sense of euphoria / well being. So powerful is our sense of taste and smell that it can in an instance transport you back 20 years to a place and detailed atmosphere where you previously tasted or smelled something. It can also trigger endorphin secretion. Smelling a freshly poured pint can make your mouth water – the start of the digestive process – even before you take a sip! The opposite is also true – smelling something repulsive can be laid down in your memory permanently so that even after years have passed, if you smell something that reminds you of that smell it can trigger reverse peristalsis of the oesophagus!

The human senses are the ultimate instruments for beer evaluation, and surely will remain so. No machine can replace the baffling accuracy by which the human nose can recall intensities and types of aromas. It is thus crucial that you train your senses in identification and filing away for later recollection of smells and tastes of importance to beer and brewing. Taste and smell is big business today. Think of the billions of rand involved in the perfume industry. The ultimate enjoyment that you will experience every couple of hours for your whole life is the tasting of food and drink. Most of us involved in the brewing industry drink beer because we enjoy the taste and flavour – we don’t drink for effect per se – although it is a welcome fringe benefit! The motto: Flavour Sells! might not always be the truth. Lite beer was successfully launched all over the world using very creative advertising campaigns often linking it with sport stars. In this instance it is actually lack of flavour that sells. Without these strong marketing actions lite might normally be perceived as just flavourless, watered down beer. Thus; the blander the product the greater need for creative advertising to sell it.

Historical Preview

Here are some of perhaps the first written records we have that our ancestors’ evaluated beer and associated the taste with something else. When the Romans invaded England in the year 100 A.D. they brought with them big supplies of wine – but soon their supplies ran out and they began to consume and brew what was then viewed as a thoroughly uncivilized drink. The Emperor Julian wrote that “this wine made from barley smell of goat”.

Thomas Becket, who later became the Archbishop of Canterbury, went on a diplomatic mission to France in the year 1158. He took with him 2 chariot loads of ale, brewed from choice fat grain – as a gift to the French who wondered at such inventions! “A drink most wholesome, clear of all dregs, rivalling wine in colour and surpassing it in flavour!

Do’s and Don’ts of Beer tasting for evaluation purposes

1. The best time to taste beer is in the morning when your senses are the sharpest.
2. You have to be stone cold sober because alcohol numbs the senses.
3. You should be slightly hungry, then your appetite is at its peak. Your senses will be in a state of anticipation of the tasting experience. When you think of a tasty pint your mouth waters!
4. Strong toothpaste and smoking numbs the palate – avoid for at least two hours.
5. Spicy foods like garlic, cloves, onions and chillies: all a no-no for 12 hours before the tasting.
6. Use a tongue scraper regularly to remove old mucus build-up on the taste buds that will impair taste sensitivity.
7. Don’t wear strong aftershave lotion or perfume.
8. Do taste away from main smell areas of the brewery. The olfactive sense is quickly saturated with aromas present. A quiet, well lit, neutral area is ideal.
9. Chew a piece of plain white bread and rinse the mouth with clean cool water between beers to clean the palate.
10. The beers should be poured, evaluated and scored one at a time.
11. Use blind tasting whenever possible. They say a glance at the label is worth a 100 years of tasting experience. You get closer to the truth with blind tasting.
12. Taste beers in order of lightest to heaviest so that what has gone before does not overwhelm that which is to come.
13. Taste in trade as often as possible – ask the regular drinkers an opinion.
14. Taste wort, green beer and beer at every stage of production to form a library of tastes and aromas for fault identification.
15. Practise, practise, practise!

Actions During Beer Evaluation

1. Aroma

The aroma is the best assessed when the beer is freshly poured from the bottle into the tasting glass. You should get your impressions down immediately. You can close the glass with your hand; give it a swirl, then give one good strong sniff, inhale deeply.

2.Appearance

Now you can hold the glass up against strong light and evaluate appearance (clarity) and colour at leisure.

3.Tasting

Tasting comes last because it is the best and most important part of the evaluation. Slowly take one small sample in your mouth, roll around and swallow. Base your impressions on this. If you want to refresh your memory on the beer let time pass and refresh your taste buds with water.

4.Mouth aroma

Beer aroma shows itself twice, once when you take a sniff (nose aroma) and secondly when the beer is entrapped in the mouth and the aromatics pass to the olfactive zone via the anterior nasal passage. Accentuated mouth aroma can be practised by slurping beer from a large tablespoon into the mouth.

5.Overall Balance

Balance is probably the most fundamental characteristic of any beer. The expected balance differs from style to style and it is crucial that a reputable taster correctly interprets the required balance for each style of beer. You always taste bitter and sweet together in different proportions according to the brewer’s interpretation of style or unique design.

6. When the formal evaluation is over and you’ve scored the beers, forget all the technical ramble and just enjoy what’s on offer for what it is.

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Brewery bacterial contaminants
By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton Pretoria, January 2004

Bacterial cells are the oldest inhabitants of planet earth. Rocks which were found by geologists in the Baberton area, timedated to be 380 million years old, showed the familiar rod shaped bacterial cells clearly when examined under a craftscope. Bacterial cells were here first and the fact that they still thrive today is evidence of their incredible ability to adapt. Some are found in the ice on the poles, others in the hot geysers that spew 100°C water, where nothing seemingly can survive.

French scientist Louis Pasteur is the father of modern brewing. His work on yeast allowed brewers to understand, for the first time, exactly what happened during fermentation. Previously beer frequently went off and became undrinkable and the brewers had no idea why. Most brewing companies in those days (and some home-brewers nowadays!) expected losses of 20% or more through waste and regularly had to destroy whole batches of sour beer.

The old saying that cleanliness is next to Godliness is especially applicable in the running of a brewery. Some brewers have dubbed themselves as glorified janitors! The brewer himself, with the degree of craftbiological control he practices during the entire process, controls the nature and magnitude of bacterial contamination in a brewery fermentation. It is a small consolation for a brewer to know that the number of bacterial genera that could survive in a brewing process are relatively small. Then again, brewing processes, as practiced by some brewers seriously lack sufficient craftbiological checks. Several factors account for the limited growth of bacteria during a brewery fermentation. Such spoilage organisms may be sensitive to hop resins (the higher the hop rate, the lower the risk of bacterial contamination), a high ethanol concentration, low pH, lack of oxygen during most of the process, limited sugar after fermentation, early heating steps and low temperature maintained during fermentation and processing.

Just on a pronunciation note. It doesn’t matter if the word is written in its original Latin form in italic or not. All “c’s” and “ k’s” for that matter are pronounced as “k’s”. Lactobacillus Bacteria (pronounced Lak-to-ba-kil-lus Bak-te-ria), craftcococcus (pronounced Mikrokokkus) Acetobacter (pronounced Aketobakter). Nowadays in normal writing the bacteria name is usually not written in italic and the pronunciation thereof, by the uninformed, has been concocted into a mix of c’s (as in sea) and k’s (as in cookie). Hopefully after studying this article you will be able to name and correctly pronounce the specific bacterial contaminant in someone’s beer at the next meeting!

In order to identify different bacteria under a craftscope, various dyes are used like methylene blue. There are some procedures (like differential staining) that use more than one stain in order to distinguish differences in the chemical composition of the bacterial cell. One of the most important differential staining techniques is the Gram stain or gram-reaction. Gram –positive bacteria that are of significance to brewing include the members of the lactic acid bacteria especially the genera Lactobacillus and Pediococcus. The important gram-negative bacteria family that have been responsible for beer spoilage are Acetic acid bacteria, Zymomonas, and a few members of the family Enterobacteriacea, Pectinatus cerevisiiphilus and Megasphaera. Certain endospore- forming bacteria belonging to the genus Bacillus and certain craftcoccus species (craftcoccus kristinae) have, on occasion caused problems in breweries.

Gram-Positive Bacteria

Lactobacillus
These are catalase-negative, nonsporulating, rod-shaped organisms that are either homofermentative or heterofermentative, based on temperature tolerance and the mode of fermentation. There are several species of lactobacilli isolated from beer, and these constitute the predominant spoilage organisms in the beer industry. They are resistant to hop bittering compounds , and some of these lactobacilli have been implicated in the production of diacetyl that is responsible for the “buttery” flavour. Although all lactobacilli produce lactic acid, the level of the acid accumulated does not reach the high threshold levels needed to make a significant flavour impact on the final beer. However, the spoilage can be observed as “silky” turbidity.

Pediococcus
These are catalase-negative , homofermentative cocci that form characteristic pairs or tetrads due to their cell division in two planes. Pediococcus damnosus is the most common spoilage organism of the genus found in breweries that produce lager beer. The organisms are seldom found in the pitching yeast, but are found at times during the late fermentation or in the final beer. The spoilage by pediococci is somewhat similar to that caused by lactobacilli. Pediococci are responsible for the sarcina sickness and give rise to high acidity and buttery aroma due to the production of diacetyl.

Other Gram-positive craftorganisms
Several gram-positive craftorganisms, although less important as spoilage organisms, have been detected in brewery fermentations. Although heterofermentative cocci like Leuconostoc mesenteroides have been detected in breweries, they are not known to produce any beer spoilage. On the contrary, Streptococcus lactis and craftcoccus kristinae, which are relatively acid-tolerant and hop-resistant, have been responsible for beer spoilage. Likewise, thermophillic endospore-forming bacilli like B.coagulans and B. searothermophilus have been isolated from breweries. These organisms are known to produce high levels of lactic acid when sweet wort is left for an extended period of time at elevated temperatures.

Gram-Negative Bacteria

Acetic Acid Bacteria
These are gram-negative, rod shaped bacteria capable of producing acetic acid from ethanol. Acetobacter and Gluconnobacter are two important genera under the group acetic acid bacteria that are traditionally associated with brewery fermentations. Acetobacter is known to oxidize ethanol to CO² and water via the hexose monophosphate pathway and TCA cycle. In the case of Gluconobacter, the hexose monophosphate shunt constitutes the most important route for sugar metabolism. The entire glycolytic and TCA cycles are not functional in gluconobacter. Beer is not expected to contain oxygen in the final form, and these organisms cannot thrive in beer under highly anaerobic conditions. Problems with Acetobacter and Gluconobacter can only be seen in beers that have low oxygen tension due to process defects.

Obesumbacterium proteus
The best- known brewery contaminant in the family Enterobacteriaceae is Obesumbacterium proteus. I have a strong suspicion that most homebrewers have encountered this bacterium some or other time. It is a gram-negative, nonacid-fast straight rod that can be found multiplying in the pitching yeast. It can grow in unhopped wort and is able to tolerate pH values ranging from 4.4 to 9.0. This organism is known to suppress the fermentation process and is also responsible for the increased level of dimethyl sulfide, dimethyl disulfide, diacetyl and fusel oils. Beer contaminated with Obesumbacterium proteus has a characteristic parsnip-like or fruity ordour.

Zymomonas
These are gram-negative rods that occur mostly as single cells, in pairs, chains, or filaments, and most strains are non-motile. Motile strains have one to four flagella. Zymomonas mobilis is the most common brewery contaminant, and its most distinctive characteristic is the ability to convert glucose or fructose to ethanol and CO² via the Entner-Doudoroff pathway. Its growth is only inhibited by around 8% ethanol. It can also be completely killed by a few minutes exposure to 60°C. Zymomonas mobilis is known to produce unacceptable levels of acetaldehyde and hydrogen sulfide in lager beer.

Other Gram-Negative craftorganisms
Several other less important gram-negative organisms have been reported in brewery fermentations. One such gram-negative contaminant is Pectinatus cervisiiphilus, which is known to produce acetic acid, propionic acid, acetoin and hydrogen sulphide, either in fermenting wort or packaged beer. Beers contaminated with this organism are generally turbid and have a rotten egg odour. The other organism of minor significance is the gram-negative coccus, Megasphaera, which imparts cloudiness and an unpleasant puke-like odour to the beer. These characteristics are primarily due to the production of butyric acid during fermentation.

What is important to remember here for us brewers is that even a bacteria described as of “minor significance” by some white-coat researcher can be emotionally devastating for a brewer trying in vain solve the mystery of his butyric smelling witbier!

References:

1. Reed, G., Nagodawithana T.W.,1991. Yeast Technology 2nd edition , p.124-126.

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A few beer faults and their origin – in a nutshell
By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton Pretoria, January 2003

Roughness:
Abnormal water composition, insufficient boil, excess tannin, excessive or alkaline sparging, insufficient kettle evaporation, hot-side aeration.

Fruity aroma /flavour:
From esters, higher alcohols, acetates of higher alcohols. The consequence of under oxygenation of the pitching yeast, too high fermentation temperature, too low pitching rate, or a deteriorated yeast strain. When unpleasant estery and combined with vegetal aroma and flavour it is from coliform contamination of the wort or yeast culture.

Celery odour:
Hafnia protea contamination, probably from tainted yeast culture.

Bitter-vegetable taste:
From deteriorated hops (oxidized beta-acids)

Buttery (diacetyl) flavour:
Where it is strong and like rancid butter, from lactic-acid bacteria – significantly Pediococcus. Slight or pleasant diacetyl flavour more often from low pitching rate, under oxygenation, petite mutants in culture yeast, or characteristic of specific yeast strain. Also from beer racked off its primary sediment too early or oxidized in the secondary.

Cardboard Taste:
Oxidation from too much air in the bottle headspace; trub carried into / lipids oxidized in the ferment; warm storage mishandling; insufficient boil; when with poor head retention, from lipids in the beer.

Sulfury aroma and flavour:
Too low on fermentation temperature; poor rinsing of sulphur-based sterilant; from wild yeast, Zymomonas or coliform bacteria. May be yeast strain specific, or from autolization of sedimented yeast. Except when from bacterial contamination, may be reduced by aging or by scrubbing with carbon dioxide.

Tinned sweetcorn ( Big Corn Bites) aroma and flavour:
Is characteristic of dimethyl sulphide (dms), from poorly malted barley especially sixrow; high moisture malt; hot wort not chilled quickly enough; coliform bacteria contamination.

Sour taste:
From too low Ph (too much acid added); from lactic or acetic acid bacterial contamination.

Medicinal aroma / flavour (Phenolic):
From wild yeast or bacteria; chlorine in the ferment either from water source or improper rinsing of chlorine sterilant; plastic leaching contamination; excess of phenolic material from over sparging or weak wort boil. Accentuated by high fermentation temperatures.

Astringency:
Excessive sparging, hot-side aeration; yeast autolization, excessive or oxidized trub carried over into the ferment.

Disagreeable smell / taste; turbidity, acidity:
Pediococcus or Bacillus contamination of the primary ferment.

Green apple flavour:
From acetaldehyde, the principal volatile acid in beer. From too high a fermentation temperature; yeast strain characteristics; bacterial contamination from the ester Ethyl hexanoate.

Banana aroma / flavour:
Acetates. Yeasts strain characteristics; wild yeast contamination; too high fermentation temperature.

Thinness:
Wort extract too low; excessive mash protein digestion; dextrin-poor extract, from too low conversion temperature.

Haze:
Poor mash digestion; Insufficient boil; wild yeast; bacteria; oxidation of beer; poor starch conversion in mash.

Gelatinous precipitate:
Excessive sparging; poorly degraded hemicellulose.

Lack of head:
Excessive protein rest; over modified malt; too high on adjunct ratio; lipids in the ferment (excessive sparging or autolized yeast) over-foaming in the ferment, repeated foaming due to rough beer transfers; over-boiling; insufficient or deteriorated hops; contact with oil.

Gushing:
Excess of priming sugars; beer not fermented out before packaging; temperature fluctuation; mishandling; old infected malt; iron in water; wild yeast contamination.

Skunky odour:
Beer light-struck. Avoid direct sunlight during brewing and in package; reduce headspace.

Rotten egg odour:
Hydrogen sulphide; yeast strain characteristics; fermentation by wild yeast; weak fermentation; in bottled or kegged beer it may be from contamination by Zymomonas bacteria.

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13 Health reasons to drink beer
By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton Pretoria, February 2003

Introduction

Medical studies have over the years consistently demonstrated that moderate consumption of beer can be part of a healthy lifestyle.

1. Drinking beer is good for your liver!

Drinkers of beer can get rid of poisonous heavy metals like lead and copper up to five times more effectively than tee-totalers. Alcohol causes the small blood vessels in the liver to expand which speeds up metabolism. (Beer Net Publication, April 2001 Biological Institute, University of Charkov, Prof. Anatolij Bohkov)

2. It lowers your risk of heart attacks.

Those drinking beer on a daily basis, averaging 4-9 litres of beer per week, have the lowest rate of heart attacks. Their risk is approximately 50% lower when compared to non-drinkers. (Bobak et al 2000; Hoffmeister et al 1999; Kitamura et al 1998).

3. It prevents cholesterol from oxidizing.

Hop compounds xanthohumol and quercetin, both strong antioxidants are very effective in their ability to prevent LDL (the bad form of cholesterol) from oxidation. When LDL is oxidised it will be laid down on the artery wall causing them to narrow, thus increasing the chances of blockage and heart attacks (Miranda et al 2000). Antioxidants are thought to be able to quench and inactivate the free radicals, which may cause the types of cellular damage that can lead to both cardiovascular disease (CVD) and cancer.

4. It boosts your antioxidant levels.

Recent studies have turned its attention to the anti-oxidative role of plant polyphenols in general, their beneficial influence on various aspects of health and in particular, their role in dealing with dangerous free radicals within the body. Analysis can show how much of these good compounds are in beer- but can it be absorbed (called bioavailability) by humans and hence have a positive effect on health? Yes! The malt-derived antioxidant ferulic acid is 100% absorbed by humans (compared to 11-25% absorption of ferulic acid from a tomato). The total level of antioxidants in the blood increased significantly after just a single glass of ale, again proving that antioxidants in beer are well absorbed (Ghiselli et al 2000) Not that any person in his right mind would settle for just a single glass!

5.

5.It boosts vitamin B6; B12; folate and mineral levels.

If compared to wine and spirits, beer is the only beverage that contains significant levels of vitamins. High homocysteine (Hcy) levels in the blood are associated with increased risk of CVD. Vitamins like B6; B12 and especially folate (all naturally occurring in beer) are now recommended as part of doctors orders to be taken daily to control elevated levels of Hcy (Walker, BRI, 2001). The minerals in beer come from both the malt and the brewing liquor. The beneficial ratio of potassium to sodium is particularly important in relation to cardiovascular disease.

6. Keeps homocysteine (Hcy) levels low.

Van der Gaag and his colleagues found that drinking wine and spirits increased serum Hcy levels, where as, counteracted by folates and vitamin B6, beer consumption had no influence. A clear case of beer should be first for thirst!

7. Drinking beer boosts your soluble fibre intake and lowers cholesterol.

One of the most effective forms of soluble fibre for lowering cholesterol is betaglucan, which is the predominant form of fibre in beer. Beers with high malt content like craft beers may provide up to 30% of the recommended daily fibre intake (Gromes et al 2000).

8. Drinking beer helps combat cancer, cardiovascular disease (CVD) and other immune system attacking diseases.

Hops contain compounds that are unique and rare in nature –like prenyl flavonoids (8PN) which are phytoestrogens that are natural plant based compounds, which mimics the natural oestrogens in the body (Bingham et al 1998). The highest 8PN levels in beers have been found in dark and bitter ales and stouts and from craft breweries where whole hopping is practised.

9. Beer ensures healthy bones.

Beer has a nutritional benefit that promotes healthy bones and connective tissue (Dr Jonathan Powell, Kings College, London). Because of the brewing process, silicon is leached from barley grain in a form that is readily accessible to the body.

10. Beer protects against gallstones.

Prof. Oliver James, from the school of clinical medical studies at the University of Newcastle upon Tyne, says that beer protect against gallstones, kidney stones and the bacterium Heliobacter pylori, which is directly linked to stomach ulcers and cancer.

11. Hoppy beer protects against cataracts.

Certain hop flavonoids, in particular xanthohumol and its isomerised form isoxanthohumol, can show positive effects against heart disease, Alzheimer’s disease, osteoporosis, cataracts and certain forms of cancer.

12. Beer promotes sleep.

A famous vitaminologist Professor Steep from Germany prescribes beer (not drugs) for insomnia. Two vitamins, lactoflavin and nicotinic acid that are present in beer are the secret weapons that promote sleep. The same two vitamins also speed up bone degeneration after a fracture and prevent low blood counts. Hops in beer itself is a natural sedative that also promotes sleep.

13. Beer reduces risk of thrombosis

The flavonoids that are present in roasted malt, also to a lesser extent in hops and barley, prevent blood platelets from clamping together –making the blood less sticky – therefore decreasing your risk of blood clotting that can cause heart attacks or thrombosis.

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The role of polyphenols in beer haze formation
By Moritz Kallmeyer
Master Brewer of Drayman’s Brewery & Distillery, Silverton Pretoria, February 2003

Abstract:

Phenolic compounds are present in all vegetable foods. Polyphenols are extracts of various plants which have the ability to react with protein in animal skins to produce leather. Tannins are polyphenols and nowadays the term tannin has come to describe all polyphenols in a plant extract regardless of their ability to tan leather. Beer has a complex mixture of phenolic compounds from 150mg/L to 330mg/L in concentration. The majority (about 2/3) are malt derived especially from the husk material of the malt. The remainder (about 1/3) comes from the hops extracted during the copper boil.

Polyphenol –are they essential?

to their specific properties, brewers find polyphenols interesting technologically (foam maintenance, physical and chemical stability and shelf life). Health researchers find them interesting because phenolic compounds can act as antioxidants in the human body, for example as protective agents against the oxidation of ascorbic acid and unsaturated fatty acids. Studies proved that the intake of beer significantly increased plasma antioxidant capacity. Today we know that polyphenols are important molecules in brewing. Positively speaking they have the ability to react with proteins during wort boiling to form the hot break; during cooling to form the cold break; during post fermentation when they are involved in the formation of chill haze and permanent hazes – which can then be removed by filtration. Negatively speaking they have the ability to react with proteins to form haze in the final pakage after a period of time (expiry date). Beer remains an unstable product.

Simplistically, polyphenol is one of the two chemical entities which control the colloidal stability of beer, the other being proteins. Proteins are derived from malt and are extracted from the malt during the mashing process. The fate of proteins is subsequently controlled by other brewing processes (not the scope of this article). The generation of beer haze is due to the extremely complex bio-chemical interaction between these two entities.The majority of modern treatments used to improve the final beer stability are aimed at the removal of either half of the protein fraction, or half of the polyphenol fraction. In some breweries both fractions are treated.

Polyphenols may be conveniently divided into three classes:

1. Simple (phe)nols which are derivations of hydroxyl benzoic or cinnamic acid (mostly from malt);
2. (Flavo)nols with more complex structures (mostly from hops);
3. Proanthocyanidins, anthocyanogens, catechins and leucoanthocyanins (arises equally from malt and hops).

All of the above 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, which not necessarily are identical, can join to form a dimer. A dimer plus a monomer form a trimer and so on.

Various studies have shown that monomeric phenols 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 and proteins.

In hot water extraction of hops such as occurs when making a hop tea for dry hopping also 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.

Oxidizable Polyphenols:

Amongst the larger condensed phenols it is not only polyphenols that are problematic, but oxidizable phenols. There are not many of these oxidizable phenols in hops. It is mainly a malt problem. The simpler phenolic molecules are more polar, i.e. their relatively simple structure has more pronounced spots of unbalanced charges, and they are thus electrically dipolar. Without going into detail, polar molecules are very soluble and in fact, the vast majority of all phenolic compounds are extracted with the first runnings! Over time simple phenols will complex into polyphenols under acid conditions and oxidise and complex with protein into haze. However, good beer doesn’t last long enough for this to happen! The real problem with haze and astringency is the existing small fraction of less polar, i.e. more complex and large polyphenols. Many fingers have been pointed at Catechines (flavan-3-ols) and Anthocyanogens (flavan-3,4 diols), and especially their polymers, in the formation of haze.

As you would have gathered by now, polyphenols are not so soluble and when they are dissolved by higher Ph water (>5.5), they are repulsed by the polar medium that they are in. They thus tend to floc together (hydrophobic force) and with catalysts like metal ions and oxygen, complex with other large (and less soluble) molecules fairly quickly. This is the unsightly but essentially tasteless so called “tannin-protein haze” (it actually contains many other components of the wort). The protein neutralizes the tanning power of tannoids by forming essentially “tanned” bonds. Tannoids, on their own, have a definite dry astringent taste!

The oxidized polyphenols with tanning power (MWt 700-1000) are called “tannoids” (or tannigens) and they try to turn your tastebuds into leather. They do this by covalently cross linking proteins in your tastebuds just as they do in tanning leather and in forming haze. They were not actually intended to do this, they seem to be located in the husk fraction of malt mainly as an astringent inhibitor against fungal and bacterial attack on barley corn. Nowadays certain sorghum grain varieties are bred with high astringency as a “put off” to birds.

The oxidized polyphenols in sweet wort will “readily complex out” as hot break. Despite their size, they are a first and middle runnings extraction problem. These are best controlled by recycling wort through the grain bed, or vigorous boiling to form hot break during the boil phase.

The unoxidized, oxidizable polyphenols are less soluble and typically a late runnings problem. A large portion can survive (uncomplexed and unprecipitated) into the hopped wort, waiting for oxygen so as to cause haze and astringency problems by becoming tannoids. These are best controlled by terminating the sparge early at SG 1.010, keeping sparge water pH<5.5, keeping sparge temperature below 75ºC (as measured at the strike point on top of the grain bed and not as a reading on the hot liquor tank gauge) and crushing your malt coarse.

Factors affecting haze formation from polyphenol extraction:

Barley variety:
Levels of anthocyanogens were found to be higher in 6-row barleys than in 2-row barleys. Beers from 2-row malts thus had better colloidal stability.

Malt modification:
Well modified malts of high proteolytic ability have a greater degree of solubilisation of tannins than less well modified malts. Well modified malts tend to form less chill hazes.

Polyphenol content:
A barley variety ANT-13 which was bred with low polyphenol levels resulted in a beer with higher colloidal stability.

Milling of Malt:
The “husk fraction” in brewing literature includes the true leafy husk and the bits of fused-on pericarp/testa & aleurone layer. Many of the problematic polyphenols in the true leafy husk of malt have been leached out during repeated steeping during malting. However there are also high concentrations of problematic polyphenols in the pericarp/ testa and aleurone layers. These are some of the least modified (enzymically broken down) parts of the malt kernel and contain the least extract. As least modified, they are more likely to remain as big bits in a coarse crush. The sparge process removes extract from between and from within the kibble of the grain bed. The osmotic leaching process of removing extract (of anything soluble) from within bits is slowed down if the bits are big. The solvent (water) simply has further to penetrate. If the big bits are the “husk fraction”, which is low in fermentable extract and high in oxidizable polyhenols, then a coarse crush is beneficial for reduced polyphenol extraction. If the big bits happen to be starchy endosperm bits, then advanced gelatinization of starch is beneficial for better extract of sugar.

Brewing Liquor:
CaCl2 and CaSO4 reduce the mash pH. Calcium will precipitate oxalate and proteins responsible for haze.

Mash pH:
Measure your mash pH from a hot sample taken from inside the mashtun about 10 minutes after mashing in. (Make sure your pH probe is accurate and can handle the temperature.) Aim for 5.3 to 5.4, no higher. Remember it is the pH of the mash that matters, not the pH of the water before it enters the mash! You can alter the mash pH by addition of lactic acid to the brewing water or straight into the mashtun.

Sparging:
Stop sparge when SG drops to 1008 to 1010 and pH drops to 5.5. or you run the risk of extracting tannins that will give your beer an astringent flavour and which will increase the risk of hazes.

Hops:
The higher the anthocyanogens content of hops, the higher the “haze risk index”

Good Rolling Boil:
Boil for at least 70 minutes. Don’t boil for more than 2 hours since you run the risk of the hot break re-dissolving.

Carragheenan:
Use Irish Moss for the last 30 minutes of the boil. Many home brewers omit it because they see no difference, in many cases the reason is that they use too little. I recommend 5g per 25L boiler volume.

Protein Rest:
For well modified malt some studies recommend a rest at 40°C for 20-30 minutes followed directly by a conversion rest. I personally have good results with a 55°C rest for 20 minutes.

Chill Quickly:
Home brewers should spend more money on their chiller design efficiency than on state of the art filtration systems. Maximum cold break formation is essential to improve beer quality and stability. Even standard ales should be heat-exchanged to 14°C.

Acknowlegements:

I am greatly indebted to the authors below who gave me a better understanding of polyphenols and their role in brewing. I have unashamedly copied whole paragraphs from their articles for this write-up – simply because I could not explain it better than they have had.

1. Controlling Phenol Extraction, Charlie Scandrett, April 1997. Brisbane Australia.
2. Advances in Beer Stabilization, Mike O’Neill, February 1996.
3. Beer Hazes, Gillian Grafton, October 1995.
4. Basic Brewing Science, Dr. Trevor Wainwright, January 1998.