Faults in wine

Owen Roe Winery, Grapes in Fermentation Bins

We’ve all had wines that we didn’t like. Perhaps it smelled a little funny, or was just bland. Sometimes, that’s a wine that is just not for us, or is poorly made, but sometimes it is the result of a wine fault.

Now wine faults can arise from poor wine making, but they can also come from sources that are out, or at least somewhat out, of the control of the winemaker. We will dive into a few of these in this post.

We discussed the chemical makeup of wine in the last post. Some of those chemical reactions we mentioned can happen at a level that is not so good in wine.

Sulfur and it’s potential faults

Sulfur is often used in wine making to preserve the wine. Adding sulfur keeps wine from oxidizing and it’s rare for a wine to be completely sulfur free. Even when sulfur isn’t added small bits are produced during the fermentation process.

A little sulfur is not typically an issue, but… if there is too much, or if it starts to combine with other chemicals in the wine, it can get stinky.

Hydrogen Sulfide

Lassen Volcanic National Park
Lassen Volcanic National Park

Hydrogen sulfide (H2S) is that rotten egg smell that you might smell at a volcano or a swamp. If you have lots of sulfur in a wine and then it sits without oxygen you can get this smell. It can happen with screw caps where there is no oxygen exchange like you get with corks or if you are aging on the lees or yeast too long.

Sulfur Dioxide

burnt match
burnt match

Matches tipped with sulfur, when struck combine with the oxygen and you get that burnt match smell. In wine, you might smell this if there is too much sulfur or you might just notice it as a burning sensation in your throat. The way that you notice this is connected to the acidity of the wine. The more acid, the more SO2 you will notice.

Mercaptan

garlic
garlic

We know that the alcohol in wine is ethanol. Well, ethanol can combine with sulfur to create “ethyl mercaptan”. This is the odor that they add to natural gas so you can smell a gas leak. I know, we said that hydrogen sulfide it the rotten egg smell, and if you are like me, that’s the smell I associate with natural gas. While I hope I do not have occasion to smell a natural gas leak, that is “ethyl mercaptan” which smells like garlic or onions. And sadly for winemakers, if you get ethyl mercaptan in your wine, there is very little you can do to fix it.

TCA or cork taint

We’ve all heard of corked wines. Perhaps you thought that was the reason that at restaurants they will hand you the cork? (It’s not, actually, they show you the cork to prove the wine is from the winery. There have been times when scandalous tricksters would re-bottle a cheap wine in a fancy bottle and try to pass it off as the higher end wine. The cork, if the wine was legit, would be stamped with the winery name.)

TCA is a mold. It actually has a much longer name: 2, 4, 6 Trichloroanisole. It is typically shortened to TCA for obvious reasons. While we think of it as “cork taint”, and indeed it can grow on cork trees, it can also grow in boxes, barrels or even winery walls. Once it gets in, it’s tough to get out. If it gets into a winery it can be transferred into the wine.

What does it smell like?

Underground Wet cave
Underground Wet cave

TCA can smell like a dark, dank, musty basement, or in lighter cases might just make a wine bland or muted. It’s not harmful, luckily and cases have decreased. The estimates on wines affected by TCA vary pretty dramatically from 1% to 8% of bottles. Distributors will typically refund clients for corked wines and at the table, if a customer says a wine is corked, it is unlikely that the restaurant will argue. Hence the differences in estimates.

Bacteria that make things stinky

So most bacteria can’t survive in wine. I mean, that’s how wine got started right? Water wasn’t always safe, but fermented beverages with their high alcohol killed off most bacteria.

Well there are a couple of bacteria that can survive in wine, one we like much of the time but the other….

Acetobacter

vinegar
vinegar

This bacteria grows when ever wine is exposed to oxygen. This little bugger converts alcohol into acetic acid and ethyl acetate. Acetic acid smells like vinegar. Ethyl acetate, which can smell like florals in small quantities, can smell like fingernail polish remover when at greater quantities.

Beyond that, when ethyl acetate and acetic acid combine it’s called ascensence.

Lactic Bacteria

This bacteria is sometimes useful! Malolactic fermentation is often used to round a wine and make it less acidic. Malic acid is often found in cool climate grapes or under-ripe grapes and is like tart green apple. Lactic bacteria eat the malic acid and produce lactic acid, which is much rounder in your mouth and less acidic. It can also produce a buttery aroma.

butter
butter
Homemade sauerkraut with cumin in a glass jar, closeup
Homemade sauerkraut with cumin in a glass jar, closeup

Too much of a good thing and you get more lactic acid than you want which smells like sauerkraut. You can also get butyric acid which smells like rancid butter. Butyric acid can come from an over-vigorous malolactic fermentation, or it might be from a bacteria before pressing.

geranium
geranium

There is also the smell of crushed geranium leaves that is either caused by an incomplete malolactic fermentation or if sorbic acid has been used as a preservative, it can be from an improper breakdown of that.

Other stinky stuff

There are other stinky things caused by stuff in wine. (There, that’s scientific isn’t it!?) Some of these things people like in small portions and sometimes the style of wine means that you will create one of these situations. Let’s start with those first.

Oxidization

nuts unshelled
nuts unshelled

Oxygen will dissolve into wine and when it reacts with the phenolic compounds (from the skins) it creates acetaldehyde, which smells like caramel or nuts and can cause browning. Some liken the smell to jackfruit (yuk) or bruised beat up apples. Oxidation can cause a wine to lose most of it’s fruit character. However…they use oxidation to make fino Sherry. So in that case, it’s a plus!

jackfruit
jackfruit

Maderization

A step beyond oxidation is maderization. You might recognize the word from Madeira. This is what happens when a wine is exposed to lots of heat or oxygen. You get a cooked or baked odor. When you get this in Madeira, it’s on purpose. When you get this from the wine you left in the back seat of your car that you parked outside in a parking lot in the Vegas sun…not so much. So generally this is considered a fault.

Brettanomyces

This one is tricky. Brett (it’s nickname) is a wild yeast. It shows up in wineries and can smell sweaty or horsey and will ferment right alongside the wine yeast.. Some people like a little brett, (I do). It gives that barnyard smell to red wines. Some people believe it to be a fault regardless of the level. It can smell medicinal or like band-aids or it might just deaden the flavors in the wine.

UV Damage

Wet Lamb
Wet wool (in it’s most natural form)

Sometimes this is called Light Strike. This happens in light white wines if they are exposed to light or UV rays. It will make the wine smell like wet wool. (don’t store your wine near a window!)

Other smells and causes

  • Moldy – that could be from actual mold in the winery or barrels
  • Green – using grapes that are not yet ripe can smell like leaves
  • Rubbery – this can pop up if there is too much sulfur or wines that are low in acid
  • Stemmy – underripe (unlignified) grape stems in a wine can have a green bitter smell.
  • Wet cardboard – Could be TCA (cork taint) or might be from filter pads that are not being used properly in the winery.
  • Leesy or yeasty – When you get overpowering yeast smell, that can come from too much time sitting on the lees (dead yeast cells). While this is good in Champagne and some sparkling wines, it’s not always good in other wines.

All in all if you get a bottle of wine and you think it has a fault, you should send it back. Too often people get a faulted wine, and will write off the region or the type of wine, thinking they don’t like the region. If you know these faults, you can tell the cause and distinguish from from the region or area. It would be horrible to write off an entire region over one bad bottle!

We will be continuing our series of educational posts on wine in all it’s complexity! Join us to explore and learn more about this fantastic and fascinating liquid.

As always be sure to follow us on Facebook, Instagram and Twitter to keep up to date on all of our posts.

The chemistry of wine

Roussanne grapes at Elephant Mountain Vineyard

Wine. It’s simply crushed and fermented grapes.

Yep, that was me.

That’s the first line in our Crushed Grape Chronicles trailer that we put together….years ago. And it’s true…mostly. (whole berry ferments do happen, but eventually the weight of the grapes on the grapes causes them to be crushed.)

So wine is made of 5 major components that go through some chemical changes, fermenting and such and create the tasty libation that we have all grown to love in all of it’s many forms.

5 major components of wine

Yes, there are other things you might find in your wine, but for the most part it’s these:

So wine is made of 5 major components that go through some chemical changes, fermenting and such and create the tasty libation that we have all grown to love in all of it's many forms.
So wine is made of 5 major components that go through some chemical changes, fermenting and such and create the tasty libation that we have all grown to love in all of it’s many forms.
  • Water
  • Alcohol
  • Acid
  • Sugar
  • Phenolic compounds
So wine's a liquid, right? So as you would expect wine is a good portion (80-90%) good old H2O. This is mostly the water that came in the grapes (thank you mother nature), but upon occasion a winemaker might water down the initial grape juice or add water if the alcohol or phenolic compounds are too high for them.

So as you would expect wine is a good portion (80-90%) good old H2O.

So wine’s a liquid, right? So as you would expect wine is a good portion (80-90%) good old H2O. This is mostly the water that came in the grapes (thank you mother nature), but upon occasion a winemaker might water down the initial grape juice or add water if the alcohol or phenolic compounds are too high for them.


Alcohol

Alcohol makes up 8 - 15% of the volume of wine. On the label you will see the abv (alcohol by volume). 8 % might be a cool climate white wine and 15% a warm climate red.

This is one of the things we love about this beverage, the slight (or maybe not slight, depending on your style of drinking. We encourage moderation.) intoxication that comes with drinking it. That comes from the ethanol which is created in the alcoholic fermentation and is the main alcohol in wine (you will find glycerol, methanol and fusel alcohols in smaller amounts). The ethanol induces feelings of pleasure. As you drink, it is absorbed into your bloodstream and travels to the brain and relaxes you.

Of course too much…and you get drunk, which is rarely fun for the people around you.

Alcohol makes up 8 – 15% of the volume of wine. On the label you will see the abv (alcohol by volume). 8 % might be a cool climate white wine and 15% a warm climate red.

Ethanol is also a volatile compound, so it evaporates really easily and it helpful in getting all of those aromas to your nose.

Alcohol also with affect the “body” of a wine. You know how water and milk feel different in your mouth? Well higher alcohol takes the feeling in your mouth, closer to the milk end of the spectrum. You can see this when you swirl in big thick “legs” or “tears” running down the sides of the glass.


Acid

Acids make up just a bit of wine .5% to .75% by volume and there are two ways of measuring it.Acid keeps wines from tasting flabby. It gives wines that tart zing. Like a bright NZ Sav Blanc that is tart and tangy and so refreshing.

Acids make up just a bit of wine .5% to .75% by volume and there are two ways of measuring it.

  • TA – Total Acidity: which is the total amount of acid by volume
  • pH – the combined strength of the acids present

Keep in mind that some acids are stronger than others so TA is just the amount, and doesn’t give you the strength. So these are typically used together.

When you measure a wine’s pH keep in mind that the lower the pH, the stronger the acid. Wine typically lands between 2.9 and 3.9 on the pH scale, and a wine at 2.9 will be more acidic than a wine at 3.9.

When you measure a wine's pH keep in mind that the lower the pH, the stronger the acid. Wine typically lands between 2.9 and 3.9 on the pH scale, and a wine at 2.9 will be more acidic than a wine at 3.9.

More than one type of acid

There are 6 main acids that can be found in wine. Some of them are found in the grapes themselves and some are created during the fermentation process. A couple straddle that line.

  • Tartaric acid – This is an acid found in both grapes and wine, and it is the most prevalent. It is the strongest acid in wine when you talk pH. If you have ever seen “wine diamonds” little crystals on a cork, that comes from this acid. While not a fault in a wine, winemakers can avoid these forming by using “cold stabalization” or cooling down the wine before bottling.
green apples
green apples
  • Malic Acid – This is a grape acid. It’s sharp taste is like that of green apples. This acid decreases as grapes ripen, so cool climate white grapes and underripe grapes will have high levels of this acid. (Later we will discuss malolactic fermentation, which is used to lower the malic acid in a wine)
oranges
oranges
  • Citric Acid – Yes the acid that you find in citrus fruit. It’s not normally thought of in grapes because the quantities are so small that you can only find it with super specialized fancy equipment. However…sometimes it’s added to pump up the TA in a wine (just not in good wine).
  • Lactic Acid – You don’t find this acid in the grapes, but…remember I mentioned malolactic fermentation? Well…lactic acid bacteria munch on the malic acid and turn it into lactic acid, which is smoother, rounder and less acidic. This malolactic fermentation can be on purpose or not, but it is often used by winemakers to soften a wine. You also might get a buttery aroma and a creamy texture (think some chardonnays)
vinegar

vinegar

Acetic Acid – You will recognize this acid from vinegar (well, most vinegars). This is a fermentation acid, so you won’t find it in grapes on the vine. It can contribute to a wine’s bouquet as it evaporates quickly, but sometimes there is another pesky bacteria, this time acetobacter that can cause a reaction between the ethonol and oxygen that can ruin a wine.

  • Succinic Acid – This guy can be found in grapes and can also be created during fermentation. It’s found in small quantities in either case and is sharp as well as slightly both bitter and salty.

Sugar

There are two main sugars that you find in grapes

One of the measurements winemakers take to determine if a grape is ready to harvest is measuring it’s brix or sugar levels. Typically this will be 15% to 28%.

There are two main sugars that you find in grapes

  • Glucose
  • Fructose

These are both monosaccharides or simple sugars and are, lucky for us, highly fermentable! Those beautiful yeasts convert the sugar to ethanol. If they finish the job, eating up all the sugar, you get a dry wine. If not, you get a little residual sugar, leaving a little sugar in the wine and thus, a little sweetness. Typical detection of sweetness in a wine is at 1% rs, but some people can detect is at lower levels up to .5%.

In some cases, the winemaker might want a little sugar left in the wine to perhaps balance a high acid level. In some cases they are looking to make a sweet wine and in that case they can leave up to 24% rs in the wine (think late harvests, ice wines or Sauternes). Sometimes…in less lovely wines, the sugar might be there to cover up a sucky wine. We are suckers for sugar.


Phenolic Compounds

Okay, here's where the real flavor comes in. Phenolic compounds come mostly from the skins and seeds and stems in the wine. They are also accountable for the color in a wine. These molecules are wide and varied and might be small compared to the other components, but they have a large impact on the taste, smell and texture of a wine.Okay, here’s where the real flavor comes in. Phenolic compounds come mostly from the skins and seeds and stems in the wine. They are also accountable for the color in a wine. These molecules are wide and varied and might be small compared to the other components, but they have a large impact on the taste, smell and texture of a wine.

  • Anthocyanins – Say that one 3 times fast! These guys give red wine it’s color, from red to purple to blue. Acids do play into this also, the higher the acid, the redder the wine, the lower the more blue.
  • Flavonols – Here’s where white wines get there golden tones. They increase with sun and ripeness. Hence, a wine that is very pale, is likely either from a cooler climate or less ripe, while a golden yellow color might indicate more flavonols (I really love that word) and might be from a warmer, sunny climate and have been more ripe at harvest.
  • Resveratrol – Okay another tricky pronouciation. This compound is thought to have health benefits. You’ve seen those posts on facebook about how red wine is good for you. Well…many studies have attributed this compound to anti-aging, cancer-fighting and disease prevention. (again…remember, all things in moderation)
  • Tannins – When it comes to phenolic compounds, this is probably the one you have heard of. They, like the others are found in the skin, seeds and stems of grapes, but you can also find them in oak. These are the bitter compounds you taste when you bite into a grape seed. They will dry your teeth if you swish them in your mouth, that’s astringency. They have a natural preservative that protects wines from oxidizing. Think about cabernet, a young one is sometimes so bitter and astringent that you almost can’t drink it. But…it can age a long time and gradually round. That’s those hard working tannins that cabernet is full of. This is also a reason for aging in oak barrels as the barrels themselves can help prevent the wine from oxidizing.
  • Vanillin – sound like vanilla right? Yep, vanillin is found in vanilla beans and in oak. That’s why you get that vanilla scent in wines or whiskeys aged in oak barrels!

You can get sediment from phenolic compounds. So you buy a nice bottle of red wine and cellar it for a while (quite a while). You go back and pull it from the cellar and notice, that it looks lighter in color and that you have sediment in the bottom. This is the tannins and pigments (which are phenolics) that have polymerized (they combine into longer molecule chains and get too heavy) and dropped out of the liquid to settle at the bottom of the bottle. With a cabernet again, this is good, it will mean the wine will be less astringent.


Other stuff

There’s more in there. We are just going to talk about a few.

  • Aldehydes – When wine is exposed to air the oxidation produces aldehydes. Sometimes you want that, like when you are making Sherry or Madeira, but most of the time you don’t. If you have ever left a bottle in the heat or just on the counter open too long and come back to find it undrinkable, that would be aldehydes.
  • Dissolved Gases – CO2 in a sparkling wine is a clear example. You might see that in small quantities in a Pet Nat or even in other wines. It will make a wine feel fresh and helps to release the aromas. There are always dissolved gases in a wine, just often not in big enough quantities to notice. We talked above about oxidation, that would be dissolved oxygen. It’s the reason that winemakers add sulfur to wines. Sulfur absorbs those free roaming oxygen molecules to keep the wine from oxidizing.
  • Esters – They create all those wonderful smells in wine. Odiferous compounds that are the result of a little coupling of an acid and an alcohol. Most of the time we like these odors, but at high concentrations, they might not be as pleasant. Take ethyl alcohol, a little bit smells fruity and flowery, truly lovely, but high quantities smell like nail polish remover.
  • Sulfites – Small bits of sulfur are produced during fermentation, but just small bits. But remember I said that they protect a wine from oxidizing? Sulfur is widely used by winemakers out of necessity to protect wines from oxidation. Deal is, some people are really sensitive to sulfurs (not nearly as many as think they are, but a significant enough amount). As a result, here in the US wines with more than 10 parts per million of sulfur dioxide, must be labeled “Contains Sulfites”.

We will be continuing our series of educational posts on wine in all it’s complexity! Join us to explore and learn more about this fantastic and fascinating liquid.

As always be sure to follow us on Facebook, Instagram and Twitter to keep up to date on all of our posts.