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Wednesday, May 7, 2014

The Chemistry between us... and wine.

I don't even remember going over chemistry at any point in school. Maybe I was too busy doodling because, let's be honest here, that happened a lot. Maybe I didn't even get that far. I mean, honestly again, I graduated on a seventh grade math level. I wasn't all that good with the numbers but I was good at the doodling. I still suck balls at math and there's nothing I can really do about that but I've fallen in love with learning everything I can about everything else before I croak.

This blog entry is about wine chemistry. The tagline of this website says that it's for wine geeks and some of you might be saying "wine geeks should already know this stuff" but you know what? I was a wine geek for years before I understood or even attempted to understand wine chemistry. So there. Everybody has to start somewhere. And if I can turn a wine geek into even more of a wine geek then I've done my part in this world gone mad.

Grapes in the sun
Wine is made from grapes. It can be made from other fruits but do you really want to drink pineapple wine? No. No you don't. Grapes just have what it takes for its fermented juice to be the best around: good acidity, a wide variety of desirable flavors, and it's a sugar-making machine. 15 to 30% of a fully ripened grape is fermentable sugar, and that is what will be turned into alcohol.

Grapes are the super-star fruit of the Earth. It's said that the DNA of Pinot Noir is more complex than our own. Grapes are the #1 most cropped fruit on the planet with 70 million tons grown annually, and 80% of that is just for wine. It's needless to say that wine is kind of a big deal.

I'm tempted to get sidetracked here but let's stay focused and skip the grapevine growth cycle, the harvest, the crush and all that. Maybe someday I'll cover that stuff but right now we have a big ol' vat of grape juice. This is called a must and it needs to be fermented by yeast cells to become wine.

Some winemakers will use the yeast that naturally grows on the grapes in the vineyard and/or hanging out all over the winery. These yeasts tend to not be all that great so they'll instead use a commercial yeast. Saccharomyces cerevisiae (pictured) is the most common yeast strain used to make wine, beer and bread. Like a good contractor it's dependable, efficient and the final result is classier than the other guys.

Saccharomyces cerevisiae yeast
How do the yeasts create fermentation? It's actually a very complicated biochemical process that involves 12 different enzymes, but essentially they eat sugar and shit out ethanol alcohol and carbon dioxide. Yeah. Not even kidding (well, kinda... but not really). You're getting drunk off of yeast shit and it's friggin awesome.

Yeasts will target the fermentable sugar monosaccharides glucose and fructose. It'll go after the glucose first and then take on the twice-as-sweet fructose second. The measurement for sugar in the USA is called brix. 1° brix is equal to 1% sugar by weight in the must and this will produce about 0.55% ethanol by weight in the wine.

Non-fermentable sugars such as arabinose, rhamnose and xylose are left behind but they're in such small quantities that they're pretty much a non-factor anyways.

During fermentation the temperature of the must rises from all the energy created as the yeasts attack the sugar. It starts to bubble from carbon dioxide. When the yeasts have eaten all the sugar they begin eating each other. Fermentation completely stops when they have nothing else to consume or the alcohol level reaches 15% (an environment in which yeast cannot survive). The dead bodies of those little guys can either be removed immediately, later, much later, or not at all depending on what the winemaker is going for. If they're left in long enough, at certain point autolysis takes place naturally and flavor compounds from the deceased yeasts (that rhymes) are released into the wine. If a wine has a bread-like character (like Champagne does) then you're tasting yeast-corpse-juice, my friend.

That big ol' vat of must is now a big new vat of wine. If you want to break it down it's composed of water, alcohol, sugar, acid and phenolic compounds. 80 to 90% of the wine is the water from the grapes it came from. That would make sense because grapes in general are 70 to 80% water.

There are many types of alcohol that are in wine: glycerol, methanol, fusel oils... but ethanol (AKA ethyl alcohol) is the one that we care about. That's the main alcohol in wine and the one that gets you intoxicated. Ethanol is also a volatile compound so it evaporates into the air and brings you all those aromas from the wine. When ethanol is consumed it goes into the blood stream and heads for the brain, putting you under its influence. If you keep drinking faster than your liver can keep up then ethanol starts producing and building up acetaldehyde (oxidized alcohol) in your blood stream and that's when you get all shit-faced and bad things happen.

Methanol isn't harmful in low concentrations but it is poisonous in larger ones. This is how people got sick and died from shitty unregulated booze during the American Prohibition, when bootleggers would use methanol instead of ethanol to cut corners. It is present in wine but it's something you shouldn't worry about.

On average 10 to 15% of the wine is alcohol. However, you'll find Moscato as low as 5% and Zinfandel as high as 17%. The sugar that was not turned into alcohol is still in there as sugar. If there's less sugar left over than we can detect by tasting it then the wine is considered dry.

Ever wonder how you can tell if a wine is sweet or not (if it doesn't blatantly say so on the label)? This is actually a very real issue for Riesling consumers as it comes in both extremes. To figure this out it's as simple as looking at the alcohol content. Keep in mind that there are exceptions (such as dessert and fortified wines) but the general rule is that the lower the ABV% the sweeter it is, the higher the ABV% the drier it is. At 13% that Riesling is going to be dry as a bone, at 8% that Riesling is going to be as sweet as candy. For the millionth time, sugar is what's turned into alcohol so the lower the alcohol content then the more residual sugar is left.

Acids will balance sugar and this is why that 8% ABV Riesling may not actually taste as sweet as it technically is depending on where it's from. Riesling is naturally a very acidic and sugary grape anyways and cold climates will leave a grape with more acid and less sugar than in warmer climates. There's a shorter growing season in those chilly places, ya know. Less time to ripen. This works out great for frigid Germany and why their Rieslings are the best in the world.

Acids are very important but only a half to three-quarters of 1% of the wine is acid. They help the growth of yeast during fermentation and fend off harmful bacteria. They also have a lot of say in the stability and aging potential of the wine. There are two different categories of wine acids: Team Grape and Team Fermentation.

Let's start with Team Grape.
These are acids in the wine that originate from the grapes that the wine was made from.

Tartaric Acid is the most important acid in both grapes and wine. Here it dominates in quantity and has the strongest pH, but despite its abundance in grapes it's actually the rarest acid found in all other plants. Tartaric acid is to blame for those tartrate crystals that you see forming on a cork or at the bottom of a bottle. Those are caused by potassium acid salt from the tartaric acid and it's irreversible. They're harmless so you shouldn't be afraid of them, although the wine will have less acidity than originally intended.

Malic Acid is generally associated with green apples. What's so important about this acid is what you can do with it: Malolactic Fermentation. Despite its name it's actually not a fermentation but a conversion that happens with the initial fermentation or later. Lactic acid bacteria takes the malic acid and converts it into lactic acid and carbon dioxide. Lactic acid is richer, smoother and creamier than malic acid.

This conversion used to be only naturally occurring (if it didn't happen when you wanted it to then tough shit) until Hanzell Winery in Sonoma, California discovered how to make it happen on demand in the 1950's. Almost all reds go through MLF but only a few styles of whites. So if your Chardonnay is green apple-y and tart it never went through MLF. If it's round and buttery then it did.

Citric acid is so minute in grapes that it's rarely heard from. Sometimes it's added to wine when they feel it needs a citrusy-acidy kick but that rarely turns out well. On occasion citric acid will also go through its own conversion during Malolactic Fermentation and become diacetyl, leaving the wine all movie-theater-popcorn-salty. Salty wine is not cool.

Then there's Team Fermentation.
These are the acids in the wine that are created during the fermentation process.

Lactic Acid, as previously discussed (see Malic Acid), is less intense than Malic Acid. It's rounder and buttery and creamy. It's the main acid in yogurt, pickled cucumbers, and the end-product of muscular activity. When Lactic Acid gets out of hand in wine it smells of goat and sauerkraut. Yum.

Acetic acid is one of the most common acids found in food. Like ethanol, Acetic Acid is volatile so you can smell it. In wine it's created at low levels during fermentation but it's responsible for that unmistakable flavor and smell when a wine turns to vinegar. When wine is exposed to oxygen for a lengthy period of time, acetification takes place and acetobacter bacteria starts transforming alcohol into acetic acid... and spoiling the wine until it's vinegar.

Succinic Acid is a fermentation acid that's seen in greater quantity in red wines than in whites, but even then it's not much of a player. It's usually outshined by Tartaric and Malic Acid, as it has the same qualities but not as loud. Sometimes it combines with ethanol to form the mild, fruity mono-ethyl succinate ester. And that's that for acids, friend.

Tyrion Lannister: God of Tits and Wine
Phenolic Compounds can be metaphorically described with a quote by Varys about Tyrion Lannister: "Very small men can cast a very large shadow". They're an insanely small portion of the wine but the impact is enormous. Phenolics are also known as polyphenolics and polyphenols. They're chemical compounds that are built off of an aromatic organic compound called carbolic acid (AKA phenol).

Tannin is the most talked about phenolic compound. It's the celebrity of the group. It's the one people actually seek out. They say "I want a big Cabernet with lots of tannin." Am I right? He's a manly man and he needs a manly wine. No pussy wine for this guy.

Tannin is mostly found in trees. That's how we discovered it existed. We started using the astringency of tannin in wood to take animal hide and "tan" it into leather. Tannins are more of a group of different molecules, not just one kind. They can gather themselves together to polymerize and create larger molecules, then sink to the bottom as sediment. They can also break down into smaller molecules as well.

The tannin in wine comes from stems, seeds, skins and oak barrels. It's mostly a red wine thing because white wine doesn't see much contact with those things. You can't taste tannin but you can feel it with tactile sensations. It changes your saliva by decreasing viscosity and increasing friction, leaving the inside of your mouth to chafe against itself without its natural lubricant. So when a wine dries out your mouth then you've been a victim of the infamous tannin.

Like acid, tannins have a major impact on the wines ability to age. The tannin is the first thing to fight the tiny bit of oxygen that gets in through the cork. This, combined with polymerization, is why usually those really expensive bottles that you can keep tucked away for 20+ years are mostly from high tannin grapes such as Cabernet Sauvignon and Nebbiolo. If you open a five year old Barolo you'll have the saliva sucked right out of your mouth and you'll taste nothing, but if you wait twenty more years the tannins will have softened and it will be a thing of beauty.

Grape skins
Anthocyannins are a member of the flavanoid family and a phenolic compound that are common in plants. They're responsible for producing the red and blue in flowers and fruits of those colors. In the process of making red wine the skins are kept in contact with the must / wine to absorb the color and flavor. Thus anthocyannins, located in the grape skins, are what make red wine red. Anthocyannins are also really touchy about the pH levels around it. The more acidic the wine the more red the color (Pinot Noir), the less acidic the wine the more blue the color (Malbec).

Flavonols are yellow pigments also belonging to the flavanoid family and are what give white wine its yellow color. The most common flavonol in grapes is called quercetin. Like the hue of anthocyannins are affected by acid, the hue of flavonols are affected by the the sunlight exposure the grapes had at the vineyard. When age and oak is not a factor, white wine from cooler climates will appear lighter, clearer and straw-colored while from a hotter climate will appear darker and golden.

Both anthocyannins and flavonols are odorless and flavorless, but their anti-oxidant properties contribute to the health benefits of wine.

Any fan of the Adam Carolla Podcast will hear Dr. Drew's voice in their head say "resveratrol" every time you think of that word. Resveratrol originates mostly from the stems and seeds of the grapes so reds tend to contain ten times more than whites. Other than grapevines it's also found in peanuts and eucalyptus trees.

Resveratrol is believed to be the major component responsible for the health benefits of wine. I say "believed" because it's really not proven yet that this is the main source. It's been a key ingredient in many herbal remedies for a long time but a link to its benefits in wine only started twenty years ago and it's still being researched. (A few weeks after this blog was released, a study by John Hopkins University concluded that resveratrol is not the cause of wine and chocolate's health benefits.)

What HAS been proven is that wine protects against coronary heart disease, stroke, osteoporosis and a shit-ton of cancers. It's also known to delay the progress of dementia and Alzheimer's in those who already have it and those who have history of it in their family. All of this is dependent on drinking moderately. Drinking too much actually increases the odds of almost all of those things.

Banana suit
Specific flavors and aromas are part of the chemistry of wine, too. If you get the smell of banana on your Chardonnay then the component that makes a banana smell like a banana is in that wine. Bananas aren't in there and it never came in contact with a banana but isoamyl acetate is present. Methoxypyrazines are in bell peppers, the grass on your lawn, aparagus, Cabernet Sauvignon and Sauvignon Blanc. Norisoprenoids are in raspberries, vanilla, Chardonnay, Syrah and Pinot Noir. Monoterpenes give off floral aromas and are actually in Gewertztraminer, Muscat and Riesling. Mercaptans are in most wines and can give off nice tropical fruit, but also rotten eggs and cat piss. When acids and alcohol combine it creates volatile esters like the previously mentioned mono-ethyl succinate and isoamyl acetate. The most common ester in wine is ethyl acetate (made from acetic acid and ethanol) and it can be fruity and flowery but can also smell of nail polish remover when it wants to be naughty.

And so abruptly ends this blog on wine chemistry. I guess I could get into Sulfites here too but I need to tackle that one on its own. There's a good, long rant waiting to set a raging fire on that one. I hope you enjoyed this as much as I enjoyed gathering it all together and writing it. I love this shit.

- Joey Casco

(Youtube) Presentation by Greg Cook
stuff stored in my brain from other sources that the same brain cannot recall
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  1. That was overall a good experience to visit out to your blog and to read about the chemistry outlines and the ideas on the baking of the different recipe, this will also help in future too. Also look forward inorganic chemistry help for best chemistry help.

  2. You can make a pineapple fermentation, but you can't call it wine.
    Here the definition :
    You should know this web site. :-))

  3. Before when you say that if the chardonnay is buttery, it's because of the malolactic. Not all the time. In Burgundy all the Chardonnay and Pinot Noir go thru the malolactic, 100%, but they do not taste buttery as the California chard does. That generalization is not a good thing.

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