Beer Studies

Troubleshooting

T1. Describe and discuss the following beer characteristics. What causes them and how are they avoided and controlled? Are they ever appropriate and if so, in what beer styles? (three will be given)

                        a)  cloudiness                b)  buttery                          c)  low head retention

                        d)  astringency              e)  phenolic                         f)  light body

                        g)  fruitiness                  h)  sourness                        i)  cooked corn

                        j)  bitterness                  k)  cardboard                      l)  sherry-like

                        m) acetaldehyde            n)  alcoholic

With this question, as with all others, it is important to answer all aspects of the question so let's break it down.

Describe/discuss

what causes them

how are they avoided and controlled

are they ever appropiate

if so, in what beer styles

These points are all contained in the Off Flavor Flash Cards. It is highly recommended that you print these and frequently review them.

In addition to these flash cards, here are some other discussions, mostly from the study guide (did I say that that is a great resource!!!)

a) cloudiness

Describe/discuss
- in Appearance - Cloudy, hazy
what causes them
- Chill haze: - Insufficent conversion time
- Permanent Haze: - excessive or high temperature sparge
- Bacterial/ wild yeast contamination
- Poor, wrong, weak or mutated yeast strains
- Wheat malt

how are they avoided/controlled
- Longer mash
- Use protein rest
- Use clearing/fining agents
- Use filtration
- Reduce sparge temps
- Practice good sanitation
- Use well-flocculating yeast

are they ever appropiate
- Yes

if so, in what beer styles
- Wheat Beers, Lambics, American Wheat

b) buttery

Diacetyl: This compound is responsible for an artificial butter, butterscotch or toffee- like aroma and taste. At low levels, it may also produce a slickness on the palate. A significant number of tasters cannot perceive diacetyl at any concentration, so every judge should be aware of his or her limitations. Diacetyl is a fermentation by-product which is normally absorbed by the yeast and reduced to more innocuous diols. High levels can result from prematurely separating the beer from the yeast or by exposure to oxygen during the fermentation. Low FAN levels or mutation may also inhibit the ability of yeast to reduce diacetyl. Note that high fermentation temperatures promote both the formation and elimination of diacetyl, but the latter is more effective. For that reason, lager breweries often employ a diacetyl rest, which involves holding the beer in the 50-55 F range for a few days after racking to the conditioning tank. Diacetyl is also produced by some strains of lactic acid bacteria, notably Pediococcus damnosus. Low levels of diacetyl are permissible in nearly all ales, particularly those brewed in Scotland, and even some lagers, including Czech pilsners and Vienna-style beers.

Diacetyl is produced at the beginning stages of fermentation and then later reduced. Maintaining or even increasing the temperature at the end of fermentation can help in its reduction, as will not prematurely removing the beer from the yeast. Oxygen reintroduction can cause its formation through oxidation of diacetyl precursors present in the beer. Ensuring the presence of adequate amounts of amino acids will also help prevent its formation. Extract brewers can often have problems due to the lack of amino acids in the extract. Lastly, diacetyl can be produced by some strains of bacteria. Again, proper sanitation and control during yeast propagation will help minimize its presence

2B. Bohemian Pilsener Some diacetyl is acceptable, but need not be present
8A. Standard/Ordinary Bitter Generally no diacetyl, although very low levels are allowed.
8B. Special/Best/Premium Bitter Generally no diacetyl, although very low levels are allowed.
8C. Extra Special/Strong Bitter (English Pale Ale) Generally no diacetyl, although very low levels are allowed.
9A. Scottish Export 60/- low diacetyl aroma, ... (optional).
9B. Scottish Export 70/- low diacetyl aroma, ... (optional).
9C. Scottish Export 80/- low diacetyl aroma, ... (optional). and is sometimes accompanied by a low diacetyl flavor component
9E. Strong Scotch Ale . Caramelization often is mistaken for diacetyl, which should be low to none.
10C. American Brown Ale Moderately low to no diacetyl.
11A. Mild---- Very low to no diacetyl
11B. Southern English Brown Low to no diacetyl
11C. Northern English Brown Ale aroma Very low to no diacetyl -- low diacetyl (especially butterscotch) is optional but acceptable.
12A. Brown Porter Diacetyl should be moderately low to none
12B. Robust Porter Diacetyl should be low to none
13B. Sweet Stout Diacetyl low to none
13C. Oatmeal Stout . Diacetyl medium-low to none
13D. Foreign Extra Stout Diacetyl low to none
14A. English IPA Very low levels of diacetyl are acceptable

17B. Flanders Red Ale Diacetyl is perceived only in very minor quantities, if at all, as a complementary aroma/flavor.
17C. Flanders Brown Ale/Oud Bruin Diacetyl is perceived only in very minor quantities, if at all, as a complementary aroma/flavor.

19A. Old Ale Diacetyl low to none
19B. English Barleywine . Low to no diacetyl.

25A. Cyser (Apple Melomel) light diacetyl character from malolactic fermentation (optional)
25B. Pyment (Grape Melomel) light diacetyl character from malolactic fermentation (optional)

c) low head retention

Good head retention is measured in terms of the time required for the head to collapse to half of its initial height. This should be at least a minute in well-brewed and conditioned beers. The beading should also be uniform and tight, leaving lace on the glass as the beer is consumed. Good head retention is promoted by several factors, including isohumulones, high original gravity, alcohol content, dextrins and the levels of high- and medium- molecular weigh proteins. Adequate carbonation is also important. Most of these variables are style-dependent, but the brewer can increase the protein content by adjusting the length and temperature of the protein rest and using adjuncts such as flaked wheat and barley. Fatty acids carried over from the trub and unclean glassware are both detrimental to head stability, since they decrease the surface tension of the foam, causing the bubbles to collapse.
American and Continental malts are generally less modified. Continental malt is modified only to 50-75%, which retains more of the endosperm for fermentability and creates greater nitrogen complexity, but at the price of reduced enzyme activity. American six-row is also modified to between 50-75%, but the higher protein and nitrogen content of six-row gives greater enzyme strength. Both Continental and American malts require a protein rest (at ~122 F) to degrade the albuminous proteins into fractions that can be both used to promote yeast growth and give good head retention.

The most widely used malted grain besides barley is wheat, which is a key ingredient in German and American wheat beers and used in small quantities in others to improve head retention. It has sufficient diastatic power to breakdown its own proteins and starches, but since it does not have a husk, it is usually mashed with barley malt in order for an adequate filter bed to be formed during the lautering stage. The protein and beta-glucan content of wheat is high compared to barley, so a more extensive mash schedule with an extended protein rest may be needed when large quantities are used.

Cellulose, polyphenols and tannins are present in the husk and can lead to harsh flavors in the finished beer if they are leached out by hot or alkaline sparge water. Fatty acids and lipids support respiration of the embryo during malting, but oxidative off flavors and low head retention may result if excessive levels are carried into the wort. Hemicellulose and soluble gums are predominantly polysaccharide in nature and for about 10% of the corn weight. The gums are soluble, but the hemicellulose must be reduced by the appropriate enzymes into fractions that permit good head retention, otherwise they may cause clarity problems in the finished beer.

d) astringency

This flavor is a mouthpuckering sensation that is comparable to chewing on grape skins or grape seeds. It is often produced by the extraction of tannins from grain husks due to overcrushing oversparging, or sparging with alkaline or boiling water. Astringency may also be produced by polyphenols that result from spoilage by acetobacter or wild yeast. Another possible source is oxidation, in which case the responsible compounds are polyphenols and aldehydes. Finally, spices such as coriander, orange peel and cinnamon also contribute astringent flavors, but these tend to mellow with age. Note that overattenuation and low dextrin levels can increase the perception of astringency.

e) phenolic

This is an aroma and taste often compared to Band-aids (tm), medicine chest or disinfectant. Chlorophenols are particularly offensive members of this family with bleach-like flavors in addition to the ones listed above. High levels of phenols are generally produced by bacteria or wild yeast, both of which indicate a sanitation problem. Phenols may also be extracted from grain husks by overcrushing, oversparging or sparging with hot or alkaline water. Chlorinated water or sanitizer residue are possible sources of chlorophenols. Phenolic flavors are generally never desirable, the exception being the clovelike, vanilla-like or slightly smoky flavors and aromas in Bavarian wheat beers and some Belgian ales.

f) light body

The body of a beer is characterized as the fullness of the flavor and mouthfeel, and descriptors range from watery or characterless to satiating or thick. Body is technically separate from mouthfeel, which encompasses physical sensations such as astringency, alcoholic warmth and carbonation, but the combination determines how the beer stimulates the palate. The body is determined by the levels of dextrins and medium-length proteins. Lack of dextrins is caused by low saccharification temperatures, excessive use of adjuncts or by highly attenuative yeast strains. A low protein level may be caused by excessively long protein rests, excessive fining or the addition of large amounts of fermentable sugars. Light body is appropriate in American light lagers and lambics, but not in malt-accented styles such as barleywines and doppelbocks.

g) fruitiness

This is an aroma and taste that recalls bananas, strawberries, pears, apples, plums, papaya and/or other fruits. The responsible compounds are esters, which are formed from the combination of an alcohol and an organic acid. High ester levels are a product of the yeast strain, fermentation temperature, high gravity worts and the metabolism of fatty acids in the trub. These flavors are desirable in most ales, particularly Belgian and British styles, and the signature banana notes in Bavarian wheat beers are primary due to the ester isoamyl acetate. Note that esters often have solvent notes at very high concentrations.

h) sourness

This is usually perceived as a taste on the sides of the tongue, towards the rear of the mouth. The two most common acids responsible for this flavor are lactic and acetic, which both have related esters that may be perceived in the aroma. Lactic acid is produced by Gram positive bacteria such as Lactobacillus and Pediococcus, which are present in dust and saliva. Acetic acid may be produced by several contaminants, including Acetobacter, Zymomonas, and yeast in the Kloeckera and Brettanomyces families. High levels of sour and acidic flavors generally indicate a sanitation problem, but they are an important part of the profile of the lambic, oud bruin and Berliner weiss styles, and to a lesser extent, Belgian white beers.

i) cooked corn

DMS, or dimethyl-sulfide produces the aroma and taste of cooked vegetables, notably corn, celery, cabbage or parsnips. In extreme cases, it may even be reminiscent of shellfish or water in which shrimp has been boiled. DMS is normally produced by the heat-induced conversion of S-methyl-methionine, but most of this evaporates during an open, rolling boil. A closed boil or slow cooling of the wort may therefore lead to abnormally high levels. Some DMS is also scrubbed out during a vigorous fermentation, which is why lagers and cold-conditioned ales may have slightly higher levels than warm-fermented ales. Wild yeast or Zymomonas bacteria may produce high enough levels of DMS to make the beer undrinkable. Low levels of DMS are appropriate in most lagers, particularly American light lagers and pre-prohibition pilsners, but are not desirable in any ale style.
1D. Munich Helles a low background note of DMS

j) bitterness

Describe/discuss

will be tasted on the back of the tongue and the roof of the mouth

what causes them

High AAU hops - Lengthy hops times - fermentation temperature

how are they avoided/controlled

Use hops with lower alpha acids
Reduce hop boil times
Higher temperature and quick fermentation decrease bitterness
filtration reduces bitterness

are they ever appropiate

if so, in what beer styles

IPA’s Pales ales English Bitters

k) cardboard

These are perceived in both the aroma and flavor and are primarily due to the aldehyde, 2-transnonenal. This compound has an extremely low flavor threshold and is produced by the oxidation of higher alcohols. The threat of oxidation may be reduced by minimizing splashing of the hot wort or of the fermented beer while racking or bottling. This flavor is never appropriate and is rare in homebrew due to the reducing power of yeast, but it is a common flaw in many old or abused commercial beers.

l) sherry-like

This is the aroma and taste of dry sherry and is often accompanied by hazelnut or almond notes. The responsible compounds are oxidized members of the melanoidin family. This flavor is one of the few positive flavors attributed to oxidation and adds complexity to barleywines, old ales and Scotch ales. Sherry-like flavors are considered a defect in most other styles, particularly low-gravity ales.

m) acetaldehyde

This compound has the taste and aroma of fresh-cut green apples, and has also been compared to grass, green leaves and latex paint. It is normally reduced to ethanol by yeast during the secondary fermentation, but oxidation of the finished beer may reverse this process, converting ethanol to acetaldehyde. Elevated levels are generally present in green beer or if the beer is prematurely removed from the yeast. It can also be a product of bacterial spoilage by Zymomonas or Acetobacter. Background levels of acetaldehyde can be tasted in Budweiser due to the use of beechwood chips to drop the yeast before it can be reduced to ethanol.

n) alcoholic

This flavor may be detected as a spicy, vinous character in the aroma and taste and is often accompanied by a warm or prickly mouthfeel. The simplest and most prevalent alcohol in beer is ethanol, which is produced by the fermentation of glucose and other reducing sugars. Higher, or fusel, alcohols are usually present at sub-threshold concentrations, but elevated levels are associated with underpitching, low levels of dissolved oxygen prior to pitching or low levels of free available nitrogen (FAN). These deficiencies force the yeast to metabolize fatty acids in the trub as a source of oxygen and carbon, producing a greater fraction of long chain alcohols. High gravity worts and high fermentation temperatures also tend to increase the concentration of these higher alcohols through increased yeast activity. Alcoholic characteristics are desired in strong ales and lagers as long as they are not coupled with the solvent notes associated with elevated ester or fusel alcohol levels.

We are now going to spike some beers.

Sourness

Both Lactic and Acetic sourness typically indicate sanitation problems but both are appropiate in some beer styles.

Please spike two of your Cat 1 beers as follows:
Sour/Acidic, using USP lactic acid 0.4 ml (1/3. tsp of solution of 1/8 tsp. lactic acid plus 3/8 tsp. distilled water) in 12 oz of beer

Sour/Acidic, using White wine vinegar (acetic acid) 3/4 tsp. in 12 oz of beer

Remember to observe when you are sampling beer. Was it a "gusher"? What are the causes if a gusher? Sanitation is one cause so it MAY be sour/acidic, but it may also not be sour. You can smell that acidic bite, can you taste a corresponding flavor?
If you don't taste it, make your sample a bit stronger until you do. This excercise is about being able to detect, at various levels, and identify what various off-flavors/aromas are. On sourness, the nose can often detect an acidic "bite/tinge" in the aroma.

We are tasting two different sournesses here. They are different! Can you tell the difference?

Off flavors, because they can be subtle, are among the most difficult for the beginner to detect/identify. This improves with experience. This excercise is where that experience starts. Do vary the strength of the adulterant you train yourself in the art of tasting. As you gain experience you will see your thresholds drop. This is the norm.