This is your day…your hour…your minute! You love your life and want to make the most of every experience you have. Your work life is filled with challenges, and the thought of kicking back with a group of great friends and a good brew is as seductive as sex. You want it to be satisfying…refreshing…delicious!

So here you are - loving the moment! The coppery highlights of Anchor Steam dance before your eyes, enticing you to quench your thirst while its fluffy white head slowly laces the glass. This fantasy, so full of life, can be quashed in a moment if your beer is served flat, stale, or has an off-flavor that you just cannot seem to identify.

What makes beer flat or develop off-flavors?

Before you begin your investigation into the realm of flat beer or off-flavors, it is critical that you understand that these qualities are sometimes the actual characteristics of a beer’s style or signature.

Lambic beers, for instance, are dry and complex, and are almost devoid of carbonation – in other words – No Head! Mead beers are touched with the golden sweetness of honey and lack carbonation, as well. Examples of these styles are Oude Kriek of Hanssens Artisannal bvba, Dworp, Belgium; Quelque Chose of Unibroue, Chambly, Quebec; Meade of Cumberland Brews, Louisville, Kentucky, USA.

Smoky and/or clove-like flavors are inappropriate for most beer styles, but are characteristic expectations in Rauchbier, Wheat Beer, and Scotch Ales. The “green-apple” flavor of acetaldehyde is one of the flavor profiles of Budweiser by Anheuser-Busch, St. Louis, Missouri, USA and EKU-28, an eisbock made by Kulmbacher Brauerei AG, Kulmbach, Germany. The signature style of Belgian lambic beer is characterized by the sweet smells produced by Lacto bacteria, horse-blanket-leather aromas from Brettanomyces, and butterscotch and acidic flavors from Pediococcus bacteria.

It helps to “know your beer.”

Causes of Flat Beer

One of the primary causes of flat beer is a basic: the glass. This is so easy, yet so critical! Beer glasses should be kept for beer only. Using the same glass for beer as for chocolate milk is not a good idea. Wash and rinse beer glasses in an area that is separate from where you wash dishes that have been exposed to food. Hand-wash and rinse thoroughly with very hot water. Allow to air dry – lint from toweling can kill a head. One more thing – if you are eating cheeses, burgers, fries or pizza with your brew, expect the head to disappear! Grease is a head killer!

Some “flat characteristics” may be caused by a faulty pour or malfunction of storage or dispensing equipment. Holding a beer glass too close to the faucet is a definite no-no. When tapping a keg, always connect and turn on the gas supply before connecting the beer faucet. If the connection is not completed in this synchronized manner, some of the internal carbonation will be dissipated while moving the beer into the beer line. Once connected, the CO₂ should never be shut off.

Flat beer can also result from a sluggish regulator, applied pressure for the keg being set too low, a contaminated beer line or air source, or a loose tap or vent. These need to be addressed by a brewpub like a gladiator attacking a lion – customers depend on beer being treated like the precious elixir that it is!

Chill can also cause a dead head. Serving beer too cold not only kills the rocky foam, but also kills your taste-buds, so watch the temperature of your brew. Fans are great at a ball-park, but the kind that cool you down in a pub may also be moving air across the top of your glass and depleting the head.

Off-Flavors & Stale Ale

Whether you are a home-brewer or a passionate lover of beer, off-flavors do not add to the refreshing, quenching aspects of a night with a great brew. As a guide to your beer-experience, here is a list of odd-ball beer taste-sensations and their causes and cures:

Acetaldehyde – This is an intermediate compound in the formation of ethanol. If beer is not given ample time to age and condition, it develops the flavor profile of green apples or farm-fresh pumpkin. If the ethanol oxidizes or becomes contaminated with bacteria, it moves one step further, and takes on a more cidery taste. These cidery flavors may also be caused by too much cane or corn sugar in a recipe. Usual cure: longer cold storage. Note: acceptable flavor in Budweiser, EKU-28, Ephemere

Alcoholic – This profile is characterized by a hot and overly spiced flavor, accompanied by a wine-like aroma. It tends to impart a prickly feel to the lips, throughout the mouth, and in the back of the throat. When fermentation occurs at too high a temperature, higher weight fusel oils and alcohols are released, rather than lower weight ethanol. This also results from using excessive yeast. Note: acceptable flavor in Barleywines or Bocks.

Astringent – This is bitterness with a tannic quality that is felt throughout the whole mouth – not the usual bitterness from hops that is more prominently noted at the back of the tongue. It may be vinegary and intensely tart. There are multiple processes that can cause this profile: alkaline water; water that is too hot; stems or skins from fruit; over hopping during bittering or finishing processes; poor formulation or processing of ingredients; oversparging the mash. Usual cure: Removing the brown scum as it forms, thus preventing it from being stirred back in; allowing longer aging for proper conditioning.

Diacetyl – This is a buttery or butterscotch flavor that is indicative of rancid beer in lagers. It may be caused by bacterial infections that reproduce in yeast sediment. If this infected yeast is repitched, it can affect those batches.Usual cure: Agitated fermenting can reduce diacetyl, but may produce acetaldehyde. Do not repitch infected yeast strains. Note: This is a highly desirable characteristic in some ale styles!

Dimethyl Sulfides – Also known as DMS, this is a cooked vegetable flavor with a rancid character, similar to cooked cabbage or broccoli. This may be caused by bacterial infection. There is no cure at the back end. Usual cure:  A proactive approach to brewing is necessary to prevent DMS – proper sterilization, boiling wort for at least an hour (particularly when using canned extracts), and following proper fermentation processes.

Esters – These fruity profiles are generally produced by the strain of yeast used. Higher fermentation temperatures produce more fruity esters, as well. Usual cure: Increased aging and conditioning. Note: Fruity esters are highly desirable in ales. Belgian ales and German wheat beers should have banana flavors. These are produced by different yeast strains.

Grainy/Husky – A profile that is evident in all grain beers, this is the result of poor grain crushing or sparging.Usual cure: Allow the grain to age for two weeks after crushing. This will cause strong, aromatic compounds to dissipate. Note: desirable flavor of highly toasted malts.

Grassy - This profile has the characteristics of chlorophyll or freshly cut grass, sometimes with a musty aroma. It may be caused by poorly stored malt or hops, hops that were not adequately dried in proper conditions, or the result of aldehydes that produce the odor of green grass. Note: acceptable flavor characteristic in bieres de garde.

Light-struck – These cat-litter or skunky aromas are due to a sulphur-based corruption of hop flavors, the resultant effect of exposure of beer to sun or fluorescent lighting conditions. Usual cure or prevention: Using preisomerized hop extract (e.g. Miller Genuine Draftis a premier example of this process – it uses clear bottles, but is free of skunkiness);using brown glass bottles; brew in a stable, dark environment; protect wort in clear galss carboys from exposure to light.

Metallic – This taste profile is similar to sucking on a penny or a rusty nail. It may be tinny or bloodlike. It is caused by exposure to iron or aluminum surfaces, high iron concentrations in brewing water, hydrolysis of lipids in malts that have been improperly stored, or cleaning stainless steel without oxidizing the surface to reduce chemical activity.

Oxidized or Stale – These characteristic flavors span a wide gamut of sensations, from that of rotted fruits, vegetables and sherry wine to the flatness of paper and cardboard. It is caused by extra oxygen in the keg or bottle, warm temperatures, or excessive aging. Usual cure: Drink your beer! Don’t allow it to get old.

Phenolic/Medicinal – This profile encompasses a wide area of diverse tastes: smoke; clove-like; band-aid quality; plastic-like. This is the result of using chlorine-based water; contamination of plastic equipment by wild yeast strains; extraction from malt during mash and sparge, the result of boiling grains; inappropriate yeast selection; excessive use of malt. Note: Smoky and clove-like flavors are desirable in rauchbier, Bavarian wheat beers and Scotch ales.

Solvent – A sharp, acrid taste in this profile is followed by an unpleasant, harsh burning sensation that reaches toward the back of the mouth and into the throat. Usual cure or prevention: Proper sterilization; lower fermentation temperatures.

Sour or Acidic – This character profile has a sour aroma, accompanied by a tart or sharp-vinegar sensation on the sides of the tongue. The use of high levels of refined sugar, citric or ascorbic acid may cause bacterial growth, as does improper sanitization. Usual cure or prevention: Clean and thoroughly inspect equipment, kegs and bottles; avoid the use of wooden utensils on cooled wort; inspect plastics for surface scratches. Note: this is a highly desirable characteristic in Belgian lambic beer styles.

Sulphur – The stench of rotten eggs signals the presence of sulpher dioxide. This is produced in mashing and destroyed in a rolling boil. It can also derive from exposure to light, poor sanitation practices, a bacterial infection in mutant yeasts, or allowing beer to sit too long on the yeast, resulting in a breakdown of the yeast walls. Usual cure or prevention: After fermentation, allow beer to lager for a few weeks. If it is still there, dispose of the beer in your veggie garden.

Vegetal – Similar to DMS, this is the flavor of cooked corn, cabbage or broccoli that results from the use of poor quality malt or malt extract, improper sanitation, or incorrect yeast amounts when pitching. Usual cure: Obtain better malts, use longer boils, correct recipes, thoroughly sanitize all equipment, bottles and kegs.

If you are feeling a bit confused at this point, a “field-trip” to a brewpub or well-stocked brasserie is the perfect antidote. Choose a few beers that are unfamiliar to you, note their color, head, aroma, and most-prominent flavor profiles. You may even wish to take a few notes! Beer tasting is very personal – like eating! Everyone has a preferred style, and your choice is as valid as the most highly rated beer expert.

Reference:
Beer Tasting Tips: Assessing Appearance
Beer Tasting Tips: Evaluating Aroma
Beer Tasting Tips: Appraising Taste Profiles
Beer Tasting Tips - Judging Mouthfeel
Beer Tasting Tips - Impression & Drinkability
Beer Tasting Tips - Training your Taste Buds

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Moleskin Notebook, Ruled Pair

Cheers!