Off Flavors are tricky. Our club has been going through the BJCP Off flavor kit. These are some of the off flavors and information i have extensively researched to put together educational info for our club. If anyone has any feedback or correction i would love to know
Wildhops.webs.com. I have only put together 3 of the "Understanding Off flavors".
Dimethyl Sulfide (DMS) / Cooked Vegetable Flavors
Definition: DMS is common in many light lagers and is considered to be part of the character. DMS is produced in the wort during the boil by the reduction of another compound, S-methyl-methionine (SMM), which is itself produced during malting. When a malt is roasted or toasted, the SMM is reduced beforehand and does not manifest as DMS in the wort, which explains why it is more prevalent in pale lagers/ales.
Characteristics: In some styles DMS is a common off-flavor and is an important aspect of the body and flavor of the beer. The amount of DMS found in beer is lowest in British ales, 10 - 20 ppb and highest in German lagers and all-malt beers, 50 -175 ppb, while the United States' lagers generally contain 40 - 100 ppb. The flavor threshold is 10 150ppb., depends on the amount of flavor in the beer. It often has a corn like flavor or aroma. When caused by bacterial infections it can have a rancid character, like cooked cabbage.
Causes: DMS is continuously produced in the wort while it is hot and is usually removed by vaporization during the boil. It is important to not completely cover the brewpot during the boil or allow condensate to drip back into the pot from the lid. If the wort is cooled slowly these compounds will not be removed from the wort and will dissolve back in. It has been stated that for every hour of hot wort stand there is approximately 30% increase in DMS.
When caused by bacterial infection it has a more rancid character; more liked cooked cabbage or cooked vegetable flavor than corn. It is usually the result of poor sanitation.
Management: Boil at least 60min, 90min if using light kilned malts.
Make sure you have an uncovered rolling boil.
Minimize the hot wort stand time and chill to below 140 degrees ASAP.
Thorough Sanitation
Fermentation and DMS
During fermentation, the evolution of CO2 can remove and reduce the level of DMS. At moderate DMS levels of 30-60 ppb a 30-35% reduction can occur, while a 35-60% reduction can occur at higher initial DMS levels, 60-150 ppb
.
Beer Styles and DMS
Types of beers in order of there perceived threshold of DMS.
Those with the lowest thresholds are most likely to have off tastes at excessive DMS levels.
Lagers (lowest):
1. Low adjunct beers with low gravities or diluted flavor.
2. High adjunct beers with corn grits
3. High adjunct beers with other adjuncts
4. Low to medium gravity (1.040-1.048) beers - all malt
5. All malt German or higher gravity, light colored - flavored beers
6. Amber - dark flavorful beers
Ales (highest):
1. British light ales
2. American or British amber or dark ales
3. Stouts or strong flavored beers
Tasting notes:
Diacetyl
Definition: To put it simple Diacetyl is the flavoring used to create artificial butter, margarine, and popcorn flavoring. For the beer geek Diacetyl is a Vicinal Diketone (VDK). The two VDKs of primary concern to brewers are 2,3-butanedione (Diacetyl) and 2,3-pentanedione. Can be appropriate in Scotch Ales, Bitters, Dry stouts, Czech Pils and Oktoberfest.
Characteristics: Along with the buttered popcorn flavor and aroma, Diacetyl has an effect on mouth feel, often causing slickness. It doesnt take much to be detected in the beer with a flavor threshold of .1 PPM. Diacetyl is a tricky flavor to diagnose as being an off flavor because it will always be in beer at some level. Often, the question is whether the beer is suited for diacetyl or not. Diacetyl can add a buttery or butterscotch flavor to beer. If there is too much diacetyl, the beer can develop a somewhat rancid flavor fairly quick. Can be produced in Ales and Lagers.
Causes: Diacetyl is a compound that occurs naturally as part of the fermentation process, but can also be increased through bacterial contamination from lactobacillus and pediococcus. Most of the Diacetyl is produced within the first few days, when the yeasts are most active.
There are numerous factors that influence production of Diacetyl by yeast. Inadequate oxygen levels during the initial stages of fermentation or to high dissolved oxygen levels during the middle-end phases of fermentation can contribute to higher levels. Also, different yeast strains are known to produce higher amounts of VDKs such as English ale strains. Additionally, highly flocculent yeast strains will tend to settle out during fermentation and may not be available later to reduce the compounds and precursors. Fermentation temperatures that are higher than optimal for a particular yeast strain and inadequate pitching rates of yeast are the more common causes.
Management: Insure adequate time and temperature for your particular yeast strain.
Perform a diacetyl rest.
Aerate/oxygenate the wort thoroughly
Pitch adequate amount of fresh, healthy yeast (MAKE A STARTER).
Diacetyl Rest
Lagers: Raise the fermentation temperature when the beer is approximately 2 to 5 gravity points away from the final gravity and hold for 2 days at that temp. I.e. ( lagering at 48 degrees raise to 65-68 degrees). The temperature is then lowered to conditioning temps.
Ale: For an ale, the fermentation temperature is usually 65 to 70 degrees; so increasing the temperature during fermentation is not necessary. It is, however, still important to allow the beer to rest at this temperature for 1-2 days after active fermentation appears complete in order to give the yeast time to accomplish reduction.
Tasting notes:
Acetaldehyde / Green Apple
Definition: Acetaldehyde is an intermediate compound in the biochemical transformation of glucose into alcohol, carbon dioxide and energy (ATP). This process is called glycolysis. The last step in the glycolytic pathway is the conversion of acetaldehyde to ethanol (alcohol). Some acetaldehyde leaks from the yeast cell during fermentation but can later be absorbed and converted to ethanol during aging. This step regenerates NAD+ by adding hydrogen atoms to acetaldehyde to form ethanol.
Characteristics: Acetaldehyde is a compound that causes off flavors and aromas in beer, often described as tasting and smelling like green apples, cut grass or green leaves, pumpkin, Sherry or latex paint, and is sometimes described as giving beer a green character. While acetaldehyde is usually considered a fault in beer, some beer styles do use it as part of the flavor profile. The best-known example is Budweiser, but other beers such as EKU-28, Salvator and Ephemere also include acetaldehyde flavors.
Causes: Acetaldehyde is a compound formed by an intermediate step in the conversion of sugar to ethanol by yeast. Under ordinary circumstances, any acetaldehyde formed during fermentation will eventually be taken up and converted by the yeast. The most common cause is removing the beer from the yeast too early, before the yeast has a chance to complete fermentation leaving the beer tasting green.
In finished beer, the ethanol reaction can sometimes be reversed by oxidation, resulting in acetaldehyde re-formation.
Also high fermentation temperatures, over-pitching and over-oxygenation can also prevent adequate reduction of Acetaldehyde. Unhealthy yeast, poor pitch rate and inadequate yeast for selected beer I.e. (pitching 1056 into a barley wine) can also cause acetaldehyde.
Zinc deficiency is another cause of elevated acetaldehyde in finished beer. Zinc, among other nutrient roles, is a co-factor for the enzyme that converts acetaldehyde to ethanol.
Management: Pitching healthy yeast (MAKE A STARTER)
Give the beer adequate time on primary yeast cake to condition.
Long lagering will reduce
Good Sanitation
Tasting notes:
Acidic/Sour
Definition: Acetic acid is a compound that causes off flavors and aromas in beer, often described as a sour or acidic taste or a vinegar character. In fact, acetic acid is the active ingredient in vinegar.
Characteristics: This is one of the five basic tastes, and is often perceived the most 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. Appropriate for Witber, Lambics, Flanders Ale and Berliner wesse. Optional sourness ok in American wheat, Rye, Dry stout and saison.
Causes: 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. The most common causes are poor sanitization; bad yeast strain; too much corn sugar; excessive amounts of citric or ascorbic acid; high fermentation temperatures; excessive acid rest; mashing too long; use of wooden spoon in cooled wort or fermentation; storage at warm temperatures; scratched plastic bucket/furminator.
Management: Good Sanitization
Use Glass or stainless steel equipment and spoons.
Cool fermentation temps and storage
Keeping mashing times below 2 hours.
Tasting notes:
Papery/Oxidation/Sherry-Like
Definition: Oxidation is the process when oxygen combines with an element, changing the appearance of the element. Oxidation is probably the most common problem with beer including commercial beers. If the wort is exposed to oxygen at temperatures above 80°F, the beer will sooner or later develop wet cardboard or sherry-like flavors, depending on which compounds were oxidized.
Characteristics: The specific way in which oxidation impacts the flavor and aroma of beer depends on many details specific to the particular type of beer that is experiencing oxidation. If trans-2-nonenal is formed in a lighter beer, it may cause a wet paper, stale bread or lipstick-like/Cardboard flavor. Trans-2-nonenal (an aldehyde compound) has a flavor threshold of about 0.1 ppb. The aroma characteristics of many lighter beers can also be affected by oxidation. The malt character initially present in the aroma of a fresh beer may change in a way that causes the aroma to be perceived as somewhat honey-like. This is due to the formation of 2,3-pentanedione.
Darker, fuller-bodied beers tend to be affected differently by oxidation. As a darker, fuller-bodied beer becomes oxidized, rich malt flavors and aromas are replaced by sweeter, sherry-like flavors. These sherry-like flavors are the result of the oxidation of the malty-tasting chemicals in beer called melanoidins. Darker, fuller-bodied beers contain lots of melanoidins. Even in darker, fuller-bodied beers, too much oxidation of the malt melanoidins will eventually cause the original rich malt flavor of the beer to take on a more toffee-like taste, wine-like, woodsy and accompanied by a hazelnut or almond flavor/aroma.
Causes: Detrimental oxygen pick-up lurks behind every turn of the mash paddle. Excessive stirring as you mash-in or during your mash is a major potential source of oxidation in your final brew because your wort is at an awkward temperature stage when oxygen readily binds with lipids and/or melanoidins.
Packaging your homebrew presents another opportunity to introduce oxygen. A significant amount of oxygen can be introduced simply by aggressively stirring in your priming sugar, siphoning from your carboy to bucket and bottling from the spigot.
Management: Basically what you need to look out for is any splashing or foaming caused by disturbing the beer either during the brewing process or during fermentation and packaging. The only time you should be looking to introduce oxygen is immediately before pitching your yeast.
Tasting notes:
Ethyl Acetate/Solvent-like/Acetone-Like
Definition: Ethyl acetate is the most prevalent ester in beer. Ethyl acetate is used primarily as a solvent and diluent, being favored because of its low cost, low toxicity, and agreeable odor. For example, it is commonly used to clean circuit boards and in some nail varnish removers. Coffee beans and tea leaves are decaffeinated with this solvent. It is also used in paints as an activator or hardener. Ethyl acetate is present in confectionery, perfumes, and fruits. In perfumes, it evaporates quickly, leaving only the scent of the perfume on the skin.
Characteristics: Ethyl acetate is the most common ester in beer by weight, but not necessarily by flavor impact. Threshold: 33ppm. Common levels in beer: 8-70ppm. Formed by the condensation of acetyl CoA and ethanol. Smells of nail polish and solvent at high concentrations, but can have a slightly fruity aroma at low levels.
It has a solvent-like, alcoholic aroma. It can present as a harsh, burning sensation on the tongue and back of the throat.
Causes: Wild yeast contamination due to poor sanitation; high fermentation temperature, non-food grade plastic equipment in contact with the beer; open fermenter, especially after high kraeusen subsides; excessive oxygenation of the wort before pitching; oxygen in secondary fermenter.
Management: Good sanitization of equipment; only food-grade
plastic used; cooler fermentation temperatures; proper wort oxygenation; closed
fermenter.
Tasting notes:
Mercaptan/ Skunky Beer
Definition: The compound produced is MBT (3-Methyl-2-butene-1-thiol), which is very similar to the chemical butyl mercaptan or skunk spray. Volatile mercaptans are normal components of beer, contributing to aroma, and they increase on exposure to light.
Characteristics: MBT is not appropriate in any beer, but some beers, notably Heineken and Corona are packaged in light green or clear bottles, making the production of MBT and the off flavors inevitable. Most people now consider the off flavors as part of the style. The off flavor is often referred to as light-struck like a skunk or freshly-brewed coffee.
.
Causes: When natural or artificial light is allowed to penetrate the beer container and initiate what is referred to as photolysis. This photolysis reaction breaks down the natural bitter alpha acid hop constituents in the beer, leading to the formation of the compound MBT/Skunky Beer. Increased risk with clear or green bottles, sunlight on brown bottles or green bottles (Can take as little as 15min in direct sunlight for a Eurolager to develop detectable MBT)
Management: : Fermenter shielded from light; brown or opaque bottles opaque to 400-520 nm light wavelengths; isomerized hop extract; storing beer in a cool, dark place.
Tasting notes:
Isoamyl Acetate/ Bananas
Definition: Isoamyl acetate (aka: 3-methyl butyl acetate): one of the most well-known and recognized esters in beer, particularly common in Weis beers and Hefeweizens. Threshold: 1.6ppm. Common levels in beer: 0.4-6ppm.
Characteristics: Formed by the condensation of acetyl CoA and isoamyl alcohol. Smells of artificial banana, Runts banana candies, circus peanuts. Some may like the characteristics of the banana flavor and can adjust accordingly.
.
Causes: High fermentation temps are the primary cause of Isoamyl acetate especially when using Hefeweizen type yeast followed by under pitching and under oxygenation. Also Zinc aids in production of Isoamyle Acetate.
Management: To avoid insure proper yeast choice for style of beer, Ferment at the low temp range with a large starter in the 60-65 degree range. Try to avoid Hefe yeast strains like Wyeast 3068 or WLP300 if you absolutely dislike Banana aroma/flavor. For one who truly enjoys a well balanced Hefeweizen ferm at 62 degrees and banana and clove will be balanced.
Interesting Facts
When a bee stings, it leaves behind traces of isoamyl acetate at the site of the sting. The isoamyl acetate then attracts other bees to the same site, accounting for the tendency for an individual to receive multiple stings at the same point on his or her body.
Ty loves Hefeweizens
One species of Japanese honeybees defends itself from attacks by hornet predators by surrounding the hornet with a ball that consists primarily of isoamyl acetate. The ball becomes so hot that the hornet dies.
Tasting notes:
Musty/Moldy
Definition: Musty, like corked wine or a damp cellar. Also referred to as 2,4,6-Trichloroanisoles. It is produced by moulds and Actinobacteria, primarily in water distribution systems. This extremely active compound imparts a musty odor to beer that resembles that of corked wine.
Characteristics: Has a threshold of less than 0.1 ppt (parts per trillion!). Mold, mildew, musty, like mold on bread.
.
Causes: Mold can grow in beer and wort and is almost always the result of storing fermenting beer in a damp, dank area. Using extract or grain that has developed mold can impart moldy, mildewy flavors as well. Also cork-finished bottles may be the cause secondary to taited corks. Aeration of hot wort and aeration during bottling can cause musty off flavors also.
Management: Always store your fermenter in a dry, dark place. Avoid storing your fermenter in damp, dank or humid surroundings. Check all ingredients for off smells, flavors and/or discoloration prior to brewing with them. Discard any moldy grain. If mold is found in malt extract, it is recommended that it be thrown out. Moldy extract can still be used if the mold is scraped off but be prepared for off flavors in the final product. If mold is found in the fermenter or beer, it is possible to save the batch by scraping off as much mold as possible. However, by the time mold is seen, it has usually infected the entire fermenter.
Tasting Notes:
Grainy/Husky
Definition: These flavors are akin to the astringent flavors produced from the grain husks. It is noticeable in the aroma and flavor of the beer. Grainy-starches in barley malt. Husky Tannins from grain husks.
Characteristics:. A taste spectrum that includes astringent tastes, cereal or grainy tastes, and husky tastes. Unlike bitterness, astringency is present as a stimulation of the nerve endings throughout the mouth. It is not an aroma. The taste is a puckering, dry, unpleasant situation. It is a very acidic, tannic, tart sensation reminiscent of grape skins. Grainy is ok to have in beer however Husky is not.
Causes: . Excessive grain crushing; powdering the malt during crushing; sparge temperature in excess of 170 degrees; excessive sparging; high pH during sparging and mash(above 6.0); boiling grains; improper decoction mashing; improper wetting of grist during mash-in; direct-firing of mash tun without proper stirring; old beer; too many salts in water (sodium, magnesium, sulfate, chloride); iron in water.
Management: Following the same precautions to avoid astringency should help with any grainy or husky flavors. Avoid grain that has been shredded or crushed. When using homemade toasted grains, allow them to age for 12 weeks after milling to allow harsh aromas and flavors to dissipate. Cold conditioning a husky or grainy tasting beer will usually help the off flavors to fall out of suspension. Monitor PH of runoff keep it below 6. Lauter with temps between 164-170 degrees.
Tasting notes:
Metallic
Definition: Its metallic. We know what this is ☺
Characteristics:. A harsh, metallic taste noted both on the tip of the tongue and the roof of the mouth. Can be felt throughout the tongue and mouth in large concentrations. Not desired in beer. Also described as Coin-like, tinny and blood-like.
Causes: .The ferrous ion (iron) and some organic compounds formed by hydrolysis of cereal lipids in grain, and oxidation of free fatty acids. Iron or mild steel in contact with beer; freshly-scrubbed stainless that has not been allowed to oxidize; improper filtering material; high iron content in water; poorly processed grain. Aluminum pots usually won't cause metallic flavors unless the brewing water is alkaline with a pH level greater than 9.
Management: Check the quality of your bottle caps, filter your water if necessary or use bottled water if you must, and keep all of your grain stored under proper conditions to prevent or reduce the coin-like off-flavors in your beer.
Tasting notes:
Butyric
Definition: Rancid, like baby vomit. Also known as butyric acid. It is a carboxylic acid and is an important flavor compound in a number of foods in addition to beer. It is an anerobic bacteria.
Characteristics: At concentrations above 3mg/L it causes a cheesy, rancid, baby vomit, or putrid off-flavor. Butryric acid can be confused by professional tasters with Isovaleric acid,Ethyl butyrate and 2,3-Butanedione. The flavour of affected beers can be worsened by the presence of 2,3-butanedione (diacetyl), or improved by ethyl butyrate derived from metabolism of butyric acid by yeast.
Causes: Butyric acid is produced by bacteria during mashing and sweet wort separation, or during sugar syrup production or storage. It is occasionally formed as a result of bacterial spoilage of packaged beer by strictly anerobic bacteria such s Pectinatus and Megasphaera.
Management: Food plant hygiene is essential in prevention outbreaks of bacteria in syrup and brewing plants, particularly during periods of high ambient temperatures.
Isovaleric
Definition: its a short-chain fatty acid commonly found in cheese, the valerian herb, foot odor, and sometimes beer.
Characteristics: Have you ever smelled cheese in your beer? How about dirty sweatsocks? The commonly accepted threshold is about 1ppm
Causes: Most of the time, its formed when hops get old, particularly when the alpha acids degrade.
Management: use your hop supply in a timely fashion and store them properly. Store in glass container is best or air tight/food safe bags. Keep in freezer to keep long
