Wellington BJCP Study Week 8

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**Wellington BJCP study group schedule**
Week	Date	Beer styles and tasting categories	Flavours, faults, ingredients, processes and other
Week 8	14/06/2007	Light Lager, Pilsener, European Amber	How to taste beer, acetaldehyde, sulphur, DMS, mashing

[edit] Flavours and faults

[edit] Acetaldehyde


Characteristics:	Acetaldehyde has the flavour and aroma of green apples. It can also taste and smell acetic/cidery.
Chemistry:	Formed as a precursor to alcohol by the yeast, or as a product of the oxidation of alcohol to acetic acid.
Causes:	Acetaldehyde from yeast metabolism as a step in the production of alcohol from glucose has a crisp green apple flavour. If produced from the oxidation of alcohol to acetic acid, whether by oxidation or by acetobacter, this flavour will be more vinegary and less pleasant
Process:	As a product of yeast metabolism, it can be caused by the strain itself or by premature termination of the yeast's fermentation. The reaction from glucose to alcohol may be stopped at the acetaldehyde stage by factors such as oxygen depletion, premature flocculation, etc. It may also be produced by contamination by acetic acid bacteria.
Removal:	Use a good yeast strain that will attenuate the wort properly. Oxygenate the wort at yeast-pitching time. Do not splash or oxygenate the wort when racking or bottling. Long lagering periods will also reduce acetaldehyde.

[edit] Sulphury-Yeasty


Characteristics:	Strong sulfuric aroma and taste reminiscent of rotten eggs (hydrogen sulfide), sulphur dioxide, or yeast. Other descriptions include garlic, burnt rubber, shrimp-like, meaty.
Chemistry:	Formed by amino acids methionine and cysteine in the malt and by certain yeast strains and bacteria, notably Zymononas, Pectinatus, and Megasphkaera. Also formed by yeast autolysis.
High level in process:	Yeast strain; rapid temperature changes to fermenting wort; bacterial contamination; beer left on sediment; wild yeasts; high fermenter back pressure; poor oxygenation of wort at yeast-pitching time; use of metabisulfite in beer; old beer (yeast autolysis).
Low level in process:	Good yeast strain; good sanitation practice; racking off sediment before lagering; cooling lagers no more than 5 degrees per day; cold- pitching lagers; strong, healthy active primary fermentation (scrubs out the gaseous sulphur compounds).

[edit] Dimethyl sulfide


Characteristics:	Volatile sulphur-based compounds that can give beer a taste and aroma of cooked corn, celery, cabbage or parsnip and even oystery-shellfish-like in high concentrations. These include dimethyl sulfide (DMS), diethyl sulfide, and di-isopropyl sulfide. DMS is first perceived in aroma at around 30 ppb, and the other compounds at considerably lower concentrations. These compounds are undesirable in beer in high amounts.
Causes:	Wort bacteria (Obesumbacterium or Hafnia) is a major cause, especially of DMS. Coliform bacteria strains can also give a strong cooked-vegetable note. Additionally, these compounds can be formed during the kilning of green malt and during mashing. DMS is also formed by the yeast in a normal fermentation, and during slow cooling of the wort by a non-microbiological chemical reaction.
High levels due to process:	Poor sanitation (primary cause); not boiling the wort for at least one hour; covering the brew pot during the boil, long cooling times (overnight) before pitching; underpitching; contaminated yeast (especially packet yeast and recovered sediment); high moisture malt; over-sparging with water below 160 degrees.
Reduction:	Good sanitation; fresh yeast culture; open, rolling boil; quick wort cooling; high pitching rates; use of 2-row English malt; proper sparging.

[edit] Resources

Flavour resources: http://www.franklinbrew.org/brewinfo/flavorguide.html

Greg Walz's BJCP Study guide http://www.gurmania.sk/beer/berjuge.htm

[edit] Technical topics

[edit] How to taste beer

[edit] Mashing

The purposes of mashing are to:

Convert proteins
Convert unfermentable starches to fermentable sugars
Extraction of flavour compounds from grain

[edit] Key temperatures

Enzyme	Optimum Temperature Range	Working pH Range	Function
Phytase	30-52°C	5.0-5.5	Lowers the mash pH. No longer used.
Debranching (var.)	35-45°C	5.0-5.8	Solubilization of starches.
Beta Glucanase	35-45°C	4.5-5.5	Best gum breaking rest.
Peptidase	45-55°C	4.6-5.3	Produces Free Amino Nitrogen (FAN).
Protease	45-55°C	4.6-5.3	Breaks up large proteins that form haze.
Beta Amylase	55-65°C	5.0-5.5	Produces maltose.
Alpha Amylase	68-72°C	5.3-5.7	Produces a variety of sugars, including maltose.

[edit] Acid / Phytase rest (35 - 49 degrees Celsius)

Phytase in the grain breaks down phytin into calcium-phosphate/magnesium-phospgate and phytic acid. This helps to acidify the mash, especially when the mashing liquor is deficient in calcium and acid grains. Beta-Glucanases are also active at this temperature range. Historically, it has been posited that Czech and German brewers used to dip their fingers into the mash and adjust the temperature of the mash until they could not distinguish any difference between the mash temperature and their body temperature (37 degrees Celsius) or even just over it. This would be especially beneficial to the under-modified malts and pale beers brewed in Bohemia.

[edit] Beta-Glucan rest (40 - 50 degrees Celsius)

It allows glucanases to break down gums that impede run-off in the sparge. It also allows good hydration of the starch cells for later swelling parts of the mash. Beta-Glucanase works best in the temperature range of 40 C to 50 C. Holding the mash temperature for half an hour in this range before the saccharification rest is sufficient to reduce beta-glucan content significantly. Typically needed for high Beta-Glucan grains such as Oats.

[edit] Protein rest (45 - 55 degrees Celsius)

Historically used for poorly modified malts in breaking down the proteins in the endosperm. Complex proteins are broken down by proteinases into smaller polypetides. Polypetides are then broken down into peptides and amino acids. The amino acids are utilised later in fermentation, especially in yeast growth and budding. A prolonged protein rest can have the implications of degrading enzymes to far and affecting the number of proteins that contribute to head retention. The protein rest also helps release sacchrification enzymes from the endosperm.

[edit] Sacchrification rest (55 - 72 degrees Celsius)

Complex starches converted into sugars - either short chain fermentable sugars or longer chain unfermentable dextrins.

Activity of 2 principal enzymes:

Beta Amylase
Alpha Amylase

Beta Amylase works in the 55-65 degrees Celsius temperature range and favours the production of the fermentable sugar maltose. Alpha Amylase works in the 68-72 degrees Celsius temperature range and produces a variety of sugars, fermentable and non-fermentable, including the long chain dextrins that help contribute to the body and mouth feel of a beer.

[edit] Infusion mash

The mash technique traditionally used by British brewers.

[edit] Stepped infusion mash

[edit] Two step decoction mash

[edit] Three step decoction mash

[edit] Other mashing techniques

[edit] Traditional Czech Pilsner mash

[edit] Belgian Turbid mash

[edit] Cereal mash

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