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Home Brew Flavor and Aroma:

Craft beer and wine are all about the right flavor and aroma for the occasion. This FAQ guide to debugging a problem rather than as an easy to read novel. Its main intention is to help the fermentation specialist isolate the problem and fix the process issues immediately. Refer to the FAQ to understand and root cause the Faults and Undesirable Sensory Notes in you home brew

Flight of craft beer for tasting and sensory notes
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It is perceived to have artificial butter, butterscotch, caramel, or toffee aroma and flavors. Sometimes it expresses as a milky slickness on the tongue. It is caused by inadequate boiling or oxygenation of the wort. 3-7 days of Diacetyl rest (slightly raising the wort temperature ~20-25OC towards to end of fermentation) helps in controlling it, as the yeast will naturally metabolize these away. Diacetyl is often confused with kettle caramelized malty notes. A bit of training can help isolate the two very different faults.
If not taken care of, this can cause serious hangover or headache in beers.

Acetaldehyde is one of the several precursor compounds produced by yeast during fermentation. It has a green apple-like aroma and flavors and is common in young beer and mead.

Glucose >> Pyruvic Acid >> Acetaldehyde >> Ethanol

Although Acetaldehyde is a natural precursor to ethanol formation, its residual levels in the finished brew is not desirable. At excessive levels, it might even give a paint solvent/ nail polish smell. Here are the few causes for this off-flavor:

  1. Insufficient healthy yeast count. Many home brewers end up with old or improperly stored yeast. Also to save cost and time some brewers sprinkle the dry yeast on their wort. Making a vigorous starter batch and ensuring adequate oxygen and nutrients reach the yeast.
  2. Fast Pressure Brewing. A brewery under pressure to churn batches as quickly as possible tries to ferment alcohol as fast as possible. This does not give yeast enough time to metabolize the precursor compounds completely. This problem is larger for lagering than for ale.
  3. Another reason for acetaldehyde is fermenting inverted sugar instead of natural unpasteurized honey during mead making. Adulterated packaged honey is therefore avoided by mead makers.

Remedy

  • 48 hours of Diacetyl rest for lagers and ales. Slightly warm conditioning and patience are all it takes for the yeast to complete its task.
  • In mead tasting like acetone: Allow it to age for at least 6 months. High sugar and natural compounds in honey prevent yeast activity. Hence it takes it longer to clear up.
Tasting Acetaldehyde As An Off Flavor In Beer

Sulfur (H2S) – The aroma of rotten eggs or burning matches from the beverage is a result of H2S residue. It gives the beer, smell of the LPG gas, or decomposing organic waste. It is a sign of stressed yeast. The easiest way to replicate (in your experiments) is by using bread yeast to produce ethanol (stressed yeast= high sugar, high alcohol, and no oxygen). Amateurish quest to produce the highest ABV possible of adding too much sugar in wine and malt in beers will also yield these Sulfur aromas. Using the right strain of yeast, adequate oxygenation and nutrients help in keeping the problem at bay. Winemakers and brewers use a few drops of copper sulfate to remove these unpleasant flavors. However, use it sparingly because of copper toxicity regulations in food.

One of the easiest ways to get rid of this smell is:

  1. Use proper brewer’s yeast instead of baking yeast for fermentation
  2. Fine with a few drops of copper sulfate solution.

Does your homebrew have the stench/ smell of a skunk? It is a result of improper handling and storage of beverages (especially imported bottles). Hops react to riboflavin (from grain) under UV light to produce this skunk flavors. This is the reason why we keep the beers in dark bottles away from sunlight.

That being said, white wine is also very susceptible to UV light. In wine, it is called ‘goût de lumière’, which means the taste of light, especially in sparkling wine. In some light beers, patrons add a slice of lime before serving. This is to mask these skunk notes.

Ever wondered why Corona beer is served with lime? Imported beer in the clear glass gets skunk and citrus notes help mask the off-flavors.

Rotten Vegetal – Similar to cooked, canned, or rotten vegetable aroma and flavor (cabbage, onion, celery, asparagus, etc.) One whiff of the brew is all it needs to detect it. If it smells like the LPG or propane gas, then probably they have contamination issues. In wine, it is often a result of excessive contact with dead yeast post-fermentation. Breakdown or autolysis of yeast cake at the bottom is the culprit.

The industry is moving to the conical fermenter, which allows aging and storage in the same vessel without raking. Home-brewers, unfortunately, have to rake their wine every couple of weeks to remove the dead yeast (aka lees or yeast cake) sediments. If you are too worried about oxidation, pumping some CO2 in the new container before raking would help. CO2 being heavier than air provides a shield against oxidation.

Buttery, Waxy Goat Cheese: These are the buttery flavors often characteristic of wild fermentation. The yeast produces fatty acids (especially caprylic acid) to impart these notes in the brew. It is desirable in Lambic beers and prolonged cask-aged wine. Some winemakers introduce Lacto-malic culture to induce these notes. However, using improperly stored or oxidized hops can also introduce these cheesy notes.

Rancidity: smells like baby vomit or putrid smell of spoilt dairy. This is caused by butyric acid because of the breakdown of fats. It is usually caused because of contamination. Another reason is the use of oily ingredients (nuts, Choco butter, etc.) whose fat breaks down during fermentation. An untrained taster often confuses it with DMS

At low levels, it has a sweet, cooked, or canned corn-like aroma and flavor. These Sulphur based compounds are produced during germination. The precursor is SMM (S-methyl methionine) that is converted into DMS. Stale and improper malting is the primary reason for this fault. Other reasons could be improper mashing, cooling the wort slowly and wild yeast infection. It is often confused with Rancidity. You can use the stainless steel wort chiller for temperature control

This is one of the most common faults in amateur home brew. It could be because of process issues or improper bottling and storage. It is discussed in detail in the links.

Grainy, husky beers: Similar to nutty, harsh flavors of fresh green wheat. It is often prominent in home-brewers using self-malted grains. Giving the malt a 2-4 weeks rest (in paper bags) helps get rid of it. Besides, improper mashing can cause it. Avoid mashing for more than 2 hours or over-sparging with boiling water.

Estery: It is the aroma and/or flavor of any ester (fruits, fruit flavorings, or roses). I like a few banana notes with my wheat beers but too much of anything is undesirable. The usual culprit is poor temperature control. Each yeast has different thermal sensitivity. The same yeast can give clove flavors at low temperatures but banana/fruity notes at high temperatures. Maintaining lower and constant temperatures is the key to keep them manageable.

However, isolating the contribution of the fruity notes from the fruits/ flowers/ hops and that from the yeast cannot be done without access to the recipe. Making tea from the ingredients is the first step towards understanding these notes before altering the fermentation temperature conditioning.

Metallic flavors have multiple names: Tinny, coiny, copper, iron, or blood-like flavor. It makes the home brew beer and wine taste like beetroot and is generally considered undesirable.

There are two major reasons for the metallic flavors in beer and wine:

  • Equipment issue: The metal ions from your equipment could be getting leached into your brew. Remember that fermentation releases a lot of organic acids that can react with metals. Fermenting in aluminum or non-food grade fermenters is the usual culprit.
  • Even if you are using SS304 stainless steel equipment, you can sometimes get the metallic flavors if the workmanship is not good. All equipment needs to be treated for pickling or Passivation. This removes any free ions and unbonded iron from the surface of the containers. Welding, drilling, bending or any metalworking creates free unbonded ions, sharp edges, and micro-fissures from which metallic ion can be leached. Treating the equipment with full concentration (without dilution) of Anphossan will leach out any unbonded metal ions. It will also remove any stains, rust (yes freshly welded stainless steel can rust if not pickled) and bring back the shiny luster in your equipment
  • From Malt: Commercial breweries install a powerful magnet at the end of their grain mill to pull out any metallic shavings from the grain and keep these flavors at bay.
  • From Special Ingredients: Some fruits, especially the beetroot has a prominent metallic flavor and should be avoided.
  • Groundwater: In Eastern India (especially near mines), this could be an indication of groundwater contamination. Using RO water and monitoring the wort chemistry would help. New stainless steel equipment also gives these flavors, probably because of micro-scratches and free ions on the metallic body. A strong acid wash, followed by alkaline neutralization helps to remove it from the brand new equipment.

Sour/ Acidic: Excessive tartness in aroma and flavor. It can be clean (lactic acid) or sharp vinegar-like (acetic acid). PH below 3.0 is a sign that ethanol was oxidized to acetic acid and there is probably no recourse. At mild levels, pH (especially in wine) can be altered by the addition of some Calcium Carbonate (food grade chalk powder CaCO3). Vinegar CH3COOH in Latin means sour wine, which can be a reflection of how common this problem is.

If too much acetic acid is there, we will get a burning sensation in the nose, which is not desirable. In some beers like Gose, Wild Ales, Weise, and Sour Beers, a slight amount of tartness is desirable. However, do check the mashing process if the wort is getting sour. At low levels, it is often hard to distinguish between acetic acid and lactic acid sourness. Here, the smell comes handy. Lactic acid has no smell but vinegar has a distinct smell of nostrils burning.

This is usually caused by using old expired hops. At low levels of oxidation, one gets the catty notes (cat urine, tomato or grape leaves). However, at a higher level of degradation, one gets the cheesy notes. Making hop tea from the ingredients helps to identify them early. Storing hops in oxygen-free and inside a refrigerator helps counter this issue. In wine, larvae of some insects when crushed also yield similar urine like rancid bitter notes.

This could be due to a variety of reasons.

  • Firstly improper mashing leads to many unfermentable sugars.
  • Secondly incomplete fermentation due to poor yeast health. One of the easiest ways to replicate this is by using baker’s yeast for making beers from the same wort.
  • Stuck Fermentation.

Although Indians have a slightly sweet palate, excessive sweetness in beer is a flaw. To deliberately introduce residual sweetness, one could use crystal/ caramel/carapills malts. Milkshake IPA and milk stouts have added lactose (an un-fermentable sugar) to get a balanced sweet palate.

Phenolic: Spicy (clove, pepper), smoky, plastic, plastic adhesive strip, and/or medicinal (chlorophenols) like smells and flavors. German wheat beers and some English styles need these notes but often too much of a good thing is also bad. Another problem is that it can come from a variety of reasons, so debugging takes longer.

  • The culprit to the root cause is the chlorinated water, which gives medical and bleach-like aromas.
  • Second could be the yeast strains, try switching to a strain with a crispier finish. English stout yeasts are often attributed to clove flavors.
  • The third is the sanitizer residue especially iodine and chlorine. Try switching to a rinse-free sanitizer.
  • Fourth, mashing technique: Over sparging, using too hot water, or even crushing the grain too much can introduce these notes.
  • Fifth and the most obvious reason could be adding excessive spices. Spices lead to an increased warmth perception (higher perceived ABV) which is why some winemakers deliberately add excessive cloves and whole spices (garam masala) in their wine.
  • Lastly, in wine, this is called ‘Brett’ wine because of the yeast Brettanomyces strains (contamination) that were introduced in the vat.
Campden Treatment for Chlorine Removal in Brewing Water
Campden powder can be used to remove chlorine from your brewing water.

Cork taint: wine faults

Musty/ Earthly: Stale, musty, or moldy aromas/ flavors. Sometimes earthy notes like mushroom and beet are perceived. It is usually a sign of fungal contamination and should be taken seriously. If there are any wall seepage and waterlogging issues, they should be fixed immediately. Using a humidity controller and proper sanitization is also recommended.

In wine, it is called cork taint, because the cork was not kept soaked in wine during aging (bottles were kept upright instead of at a slant in the cellar). It is often caused by compounds called 2,4,6-trichloroanisole (TCA) or 2,4,6-tribromoanisole (TBA).

If there are signs of malo-lactic fermentation (small microbubbles in wine during secondary that does not disappear), then adding Potassium Sorbate (wine stabilizer) before back-sweeten can also introduce these earthly notes.

The addition of some herbs, mushroom, cannabis/weed/hemp, etc. can also introduce these Earthly flavors. A bench test of these additives can root cause the culprit.

Yeasty: A bready, sulfuric, or yeast-like aromas or flavors. It is most often because the beverage is not aged properly and has too much yeast floating around. The quickest way to get rid of them is to wait for a couple of weeks under an airlock.

Some gelatin beer fining agent and 24 hours of a cold crash (keeping finished fresh ferment in a refrigerator) often do the trick to remove these off-flavors.

Diamond: Chemically these are Potassium Tartrate crystals, at the bottom of the wine bottles. Wine with excessive levels of tartaric acid tends to exhibit these diamond/ sugar like structures during aging. The best way to get rid of them is to cold crash (24 hours at 4o C) and then bottle. It is sediment in the bottle and does not affect the sensory perception in any other adverse way. One of the reasons expensive wine bottles have a dimpled base is that these crystals are stuck to the dimple structure at the bottom and are not poured out in the wine glass.

Heat Damage: It is a common term used by experts to describe anything that they suspect was improperly stored and handled. The notes from heat damaged IPA (hoppy beers) and wine are similar to an over-aged and oxidized beverage. Hence, heat damage gets more blame than it should deserve. The best way to prevent heat damage is by storing your hoppy beers and wine at less than 13 degrees Celsius.

It is an unusual name for viscous, slimy and fatty mouth-feel in wine. It is often a result of mallo-lactic fermentation. Wine styles with excessive dextrins and polysaccharides are known to exhibit a fatty feeling on the tongue.

Ever felt a whiskey/brandy-like feeling when drinking homemade wine?
The aroma, flavor, and warming effect of ethanol and higher alcohols. Sometimes it is described as hot. It can also be a result of adding too many spices like cloves & cinnamon in the brew. It is desirable in spicy Christmas beer and heated winter wine. It is a result of high-temperature fermentation or stressed yeasts. The biggest problem is that this reduces the amount of beverage that can be gulped in one sitting. Hence, most winemakers and brewers like to keep higher alcohols to the minimum.

Astringent: Puckering, lingering harshness, and/or dryness. When in excess, it impacts the finish or aftertaste by introducing harsh graininess and huskiness. In wine, it is often a result of excessive contact with grape skins. Reducing the contact with the skins and tannins used rectifies it. In beers, it could be because of too much of peated malts, smoked or biscuit malts. Another reason could be over mash or over sparge (which releases the grain astringency). Altering the pH and a few trial batches are needed to isolate the source of this astringency (grain, hop, or water). The reason for aging wine and certain styles of beers is to mellow down this astringency through certain natural biochemical reactions. Aged bottles are more valuable because of this unique flavor profile. Saving the astringent bottles for next quarter or year is always a good idea.FAQ Details

This is probably due to Refermentation. It is a common problem in inadequately pasteurized or preserved sweet wine. This is discussed in the post on Haze and can be cured by adding potassium sorbate or stabilizer in sweet wine.

For champagne, they keep it in a rotating neck freezer so that all yeast crystallizes on the cork and when we open it, gets expelled.

Grassy: Aroma/ flavor of fresh-cut grass or green leaves. Some hops and herbs especially Saaz hops have such a feeling. Fresh hops that are not dried properly also give these grassy notes. Many Indians who grew up drinking jaljeera and herbal teas actually like these notes in their beers. Some home maltsters who use fresh inadequately dried malts also report this problem.

Watery/ Thin: It lacks the body and mouth feel. In wine, it is a result of not using enough fruits. In beers, it is a result of using too little malt or too many enzymes. Adding a bit of specialty malt like caramel/ crystal malts will rectify it. The mashing temperatures can also be altered to produce more sugars that are unfermentable.

Manure: Also called Farmyard smell. It is a sign of improper cleaning of fruits and grapes before pulping. Sometimes in fruit beers, it is a sign of improper puree making techniques. Essentially, there is a degree of composting or undesirable microbial activity. Proper sorting of fruit is recommended to isolate the composted fruits. Most farmyard wine also have other defects associated with wild fermentation.

Solvent: are aromas and flavors of higher alcohols (fusel alcohols). Similar to acetone, lacquer varnish and paint thinner aromas. It is an indication of stressed yeast and is undesirable. Cheap distilled liquor (where the last portion of the distillate is not discarded) often gives these notes. Reasons for the stress could be inadequate healthy yeast count, high gravity (too much sugar), high temperature accelerated fermentation, etc.
In mead, the common reason is the use of inverted sugars or adulterated packaged honey.

Umami: Soy sauce or Thai fish curry aromas and flavors. It primarily comes from amino acids released from the autolysis of yeast. Slight umami flavor is desirable in Sake and some aged beers but it is a difficult flavor to balance. The usual culprit is the beverage sitting over dead yeast (cake/ lees) for a few weeks. Some brewers have switched to lower protein malts & changes in mashing to reduce Umami. Conical fermenters where the yeast cake can be drained out is recommended to combat these notes.

Floating Film: It is a transparent or sometimes white/ greenish layer on top of the wine (seldom/ rare beers). These films stick to the needles or toothpicks, due to their oily nature. The most common reason is the use of oily ingredients (certain fruits, chocolate butter, and nuts) and resinous hops. These can be remedied by tweaking the recipe.

However, wild yeast or mold infection could also result in these flecks on the surface and should not be ignored. Proper sanitation and a daily ritual of stirring the wine are known to help.

Alcohol in a beer comes from the malt used and not from the hops. However hoppy IPAs (India Pale Ale) tend to be too bitter for easy gulping. Therefore most brewers add extra malt in them to balance the taste. So even though hops don’t make beer alcoholic, hoppy beers tend to have high alcohol percentages.

Fermentation is probably older than civilization and agriculture. It is a perfectly safe hobby that does not produce any poison or foul smell. When it comes to the safety aspect, follow the 4 golden rules:

  1. If the smell is funky, then it is better to discard
  2. If you see mold or a white-green-black floating film on top then discard
  3. If you are not distilling or fermenting wood or other inedible substances then one need not worry about methanol
  4. If the tastes are odd, then discard. Better safe than sorry.

People have been fermenting beer, wines, and ciders for 5 thousand years across the globe with various simple crude setup. A modern kitchen is much more hygienic and hi-tech than the early man’s setup. So if one could do a safe fermentation in a crude setup, then they can do the same in a modern kitchen. So be assured that if a recipe is followed, then a home brew will not make you sick or poison you.

  • First have a look at the SCOBY. If there are black or green patches on it, then the kombucha is most likely affected by mold and should be discarded.
  • Then look, if there are any insects, weevil or pests in the kombucha. If they are 1-2, you could probably discard the impacted portion. If there are too many, then you may have to procure a fresh mother.
  • Smell the kombucha. If it smells pleasant then you are probably OK. If it smells rotten or sewage like, then discard.
  • Trust your senses. Taste a spoon full. It should taste tart and yet refreshing.

In short, if the kombucha that you made looks OK, smells ok and tastes ok, then it is OK.

There is a huge variety of rice wine and traditions. Some like it tart, some sweet. Some like it filtered while most like it milky white. Some like it plain, while some infuse spices and a lot of people infuse flowers (floral aromas). It is hard to generalize the taste and flavors of rice. However, in general, it is a slightly tart, mildly sweet, and alcoholic beverage.

Apple Cider can be turn out bitter because of a variety of reasons. Here are some to help you out:

  1. Low Residual sugar. Sweetness is the best mask for bitterness (for example coffee and chocolate). Try using some wine stabilizer and back-sweeten your cider.
  2. Excess Tannin: Adding too much oak chips, fruit skins, and other sources of natural tannin can introduce astringency, woody feel, or bitterness in your wine/cider. The best way to reduce is by using a fining agent. IsinglassBentonite, and Gelatin can help you control excess tannin.
  3. Aging: Time mellows down all harsh flavors in cider/wine. Try aging your cider/white wine by 1-6 months and red wine by 1-3 years. With time the complex biochemical reactions will make your beverage more flavorful and amazing.
  4. Problem with the fruit: Although you can make cider/wine from any fruit, some fruits are not that flavorful. When you take the sweetness out (by converting it to alcohol/vinegar), the residual flavors start emerging. Try to experiment with a different harvest or fruit type. Mixing two or three different fruit also helps.

For more details refer to our off-flavors guide.

Fruit wine is full of aromas and flavors from the natural fruit it is made of. They are often infused with spices (especially cinnamon, ginger, star anise) which add to the complex boutique flavors that we recognize with a good cider. They taste very similar to a dry white wine but can be back sweetened to taste. If you carbonate your cider, it will taste and feel like champagne.

Unlike cider vinegar, your alcoholic hard cider should not taste sour or burn your nostrils (acetic acid). They are also not supposed to taste bitter.

कोस पर बदले पानी और चार कोस पर वाणी |
(The taste of water changes every mile and the dialect changes every 4 miles or every village you cross)

Growing up, we have seen these words as an acknowledgment of diversity in India. However, digging deeper into food-craft, we realize that this line is a tribute to our senses. Each water body, each village is different and unique and humans are sharp enough to recognize that.

Multimillion-dollar AI, spectroscopy and scores of lab equipment are very prominent nowadays. But they can at best mimic what our nose, tongue and senses can definitely detect and conclude in an instant. Human senses are tuned to detect some chemicals even in ppb (parts per billion) concentration. This page is a collection of notes on how one can hone their senses. Consequently, use it for the betterment of food-craft.

Until now, we focused on the basic recipe and flavors. We shared many options of how we could innovate. But how those ingredients expressed themselves in the final product was not explored. For food to be called a craft, we need an ability to understand and tweak the more subtle flavors and sensory notes as well. Therefore, its important to analyse the way ingredients behaved through the process.

Craft Beer Flavors Chart
Craft Beer Flavors Chart

The best way to fix any problem is to isolate it. The above list would help Brewers to critically analyze their homemade wines and home brew beers. Thus helping to observe the batch to batch variance of your finished product and tweak the processes to rectify the defects.

Most professionals use the aroma wheel. This helps explain their sensory notes. For this reason, I have published a sample wheel for your reference. While amateurs usually perceive the inner circle only, advanced home brewers perceive the middle circle. In case of professionals (who constantly train their senses) perceive the outer circle. One can use the aroma wheel as a reference guide. It helps those who might end up using similar terms to describe the same sensory notes.

Wine Flavors chart
Wine Flavors chart

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2 comments

  1. Sumit Mallik

    How much quantity sugar should be added to per 1.5 kg grapes for making wine? Please help.

    1. Sumit detailed wine recipe & instruction video is available at https://www.arishtam.com/make-grape-red-wine/home-brew-recipes/

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