But getting down to it, how is wine made?

Many of you are probably pondering a fundamental question related to this blog: how is wine made? 

In these posts, you will realize that my winemaking is not—and never will be—mistake free. My personal opinion is that winemakers of all levels of expertise have their “knyuck-knyuck” Three-Stooges winemaking moments.

I am no exception.

Winemaking, as described here, is about a process. But it’s also about creatively handling problematic situations that arise (like life, no?).  So, let’s begin, using the example of one of my vintages now safely aging and being consumed by my family and friends.

My first bit of advice on how to make good wine is to find good grapes. An incompetent winemaker will certainly turn great grapes into bad wine, but a competent winemaker cannot turn bad grapes into great wine. I make my wine using many different grape varieties from various regions in both the United States and other countries. I grow three different grape varieties in my backyard (my vineyard) and I also make wine from my pear and apple trees, although most of the time I ferment this apple and pear juice into cider.

Luckily, in making my 2010 Chilean Cabernet Sauvignon wine, I started with 360 pounds of excellent grapes from Chile, so my main task was to not muck things up.

Grape Destemming, Crushing, and Testing

In late May 2010, about 7,000 pounds of six different grape varieties (cabernet sauvignon, malbec, merlot, carmenere, pinot noir, and syrah) arrived in the Milwaukee area in a refrigerated truck from the East Coast after being shipped by boat from Chile. About 15 members of the Wisconsin Vintners Association–of which I am a member–divided up this 3 1/2 ton load of grapes for their individual winemaking. Our springtime in the Midwest is the southern hemisphere’s fall season, so it’s a grand occurrence for home winemakers in the region!

Every spring, members of the Wisconsin Vintners Association band together in purchasing about five different grape varieties sourced from Chilean vineyards. The grapes are packed in 18-pound plastic containers (called lugs) for the two-week trip to the Midwest.

Every spring, members of the Wisconsin Vintners Association band together in purchasing about six different grape varieties sourced from Chilean vineyards. The grapes are packed in 18-pound plastic containers (called lugs) for the two-week trip to the Midwest.

Upon receiving these particular grapes, I selectively popped a few into my mouth, one at a time. I tasted each, being careful to remove the seeds for visual inspection. I also chewed on the skins to become familiar with the amount and quality of the skin tannins (we’ll get to tannins in another post).

Destemmer in process

Crusher/Destemmer machine in process

I liked what I tasted.

My seeds were light brown with a tan interior. When I chewed them, they tasted nutty, leaving a good “furry” tannin-feel on my tongue. I was pleased.

The first step in the winemaking process is to separate the grapes from their stems and  gently break their skins to release the juice.

To do this for  3 ½ tons of grapes, we used an electric grape crusher/destemmer. The resulting slurry slush of crushed grapes is called “must.”

Now for some science…

In chemistry, pH is an indirect measure of the acidity of an aqueous solution, and pH levels range from 0 to 14. Solutions with a pH equal to 7 are classified as being neutral, a pH level less than 7 is becoming increasingly acidic as the pH value decreases, and a pH greater than 7 is becoming increasingly basic or alkaline. Pure water has a pH level very close to 7. Most finished wines have pH levels between 3.0 and 3.7, on the chemistry acidic side, but not too acidic (like lemon juice). Before beginning to ferment grape juice from red grapes into wine, you typically want to have a pH level in your must somewhere in the 3.30 – 3.60 range. My grape’s starting pH level was 3.47, so okay, good.

Next science lesson: The sugar in wine grapes is one of the two most important components in winemaking, because the sugar is the food for the little creatures that create the wine. Brix (°Bx) is defined as the percentage of sugar by weight in a solution. If your Brix level is 22° then 22% of your grape juice is sugar. The traditional method for determining the Brix level of grape juice is by using a hydrometer, which measures the density (specific gravity) of the grape juice. The Brix sugar level of my must was 22.6˚ (Specific Gravity, or S.G. = 1.092).

Must: the resulting slurry slush following destemming

Must: the resulting slurry slush following destemming. The must in this photo has begun fermenting, hence, all those carbon dioxide bubbles!

With this amount of sugar in my must, my finished wine was likely to have an alcohol content of about 12% – 13% (a typical wine level).

One more science lesson: Acidity provides the crisp, slightly tart taste in wine. If your wine has too little acid it will taste flat and flabby, but if it has too much acid it will taste like lemonade. There are three basic acids in wine and grape juice: tartaric acid, malic acid, and citric acid. When you measure the total acid in wine it is a combination of these three acids, and winemakers typically shoot for a total acid (T.A.) level between .45% and .70%.

Hmm…hold on…my total acidity (T.A.) in my must was only .45%. Why did this surprise me?

Uff da! A bit more wine-science discussion here (skip ahead if you “must”!):

With my pH level of 3.47, I expected my T.A. to be more in the .65%-.75% range, because that is how these two readings typically match up (not always, but typically).

So what should I do? Should I add tartaric acid (the most desirable acid) to my must to raise the total acidity closer to the more normal .65% level?

Typically, when you add tartaric acid to raise your must acid level, this also results in your pH level decreasing.  My pH level of 3.47 was already pretty low, so I decided to leave things “as is.” Often your initial sugar, acid and pH readings taken soon after grape crushing are not an accurate measure because the newly crushed grapes are still retaining much of the juice inside the skins.

First little lesson in winemaking: keep your interventions to a minimum, and when in doubt, do nothing…but remain attentive.

Pre-Fermentation Additions

My must was now in a 32-gallon food-grade plastic container and an 11-gallon bucket.

Buckets o' grapes

Buckets o’ grape must fresh from the group crush and ready for fermentation!

To retain the future wine’s color intensity and enhance what is called the “mid-palate mouth” feel, I added 30 grams of Tannin VR-Supra prior to commencing fermentation.

I also added 30 grams of Opti-Red, which is an inactivated yeast derivative nutrient used to obtain fuller-bodied, more DSC02411-1color stable, smooth-palate wines. All of these additives are in powder form that you mix with a very small amount of water prior to tossing it into the must.

Why did I add these ingredients? By reading about what wine experts recommend.

If you want to improve your winemaking efforts or learn the basics from the start, then set aside a good deal of leisure time to read how wine experts make wine and the advice they offer: knowledge is power. For the self-conscious amongst us, you could slip your winemaking readings into a stodgy financial investment manual when you are out and about in public so that stodgy people around you will think you are indeed using your time wisely (and, in fact, you are!).

I was now ready to commence fermentation.

The Fermentation Process: Too Much Heat for My Must

To ferment, you add yeast to the must, or you could allow native yeasts that are floating in the air to eventually start fermentation, but that can be very risky. Why? Because the native yeast may be “funky-funky” yeast (not a technical term, but rather, my own term for bad, thuggish yeast that will rip out the heart of your must while laughing).Ok, back to regular yeast. Yeast are tiny micro-organisms that convert the sugars in grape juice into alcohol and carbon dioxide through the process of fermentation. Yeast is the second of the two most important components in winemaking (remember, sugar was the other).

I added 30 grams of Go-Ferm Protect (a natural yeast rehydration nutrient) and 24 grams of Lalvin Bourgovin RC 212 red wine yeast (a low-foaming moderate-speed fermenter that allows for full extraction of grape compounds). This yeast ferments between 68˚ – 86˚ F and in an environment that has up to 14% alcohol; this particular yeast begins to die at higher alcohol levels. Fortunately,my must sugar level was low enough so that the yeast would not produce that dangerously high alcohol level.

The next morning my must temperature was only 72˚. This was too low to extract some of the good compounds from the crushed skins, so I decided to add heating pads around my fermenting buckets (in the photo below). Within four hours, the must temperature had increased to 82˚.

DSC02400That’s good.

But then I made a mistake; I kept the heating pads on! (“knyuck-knyuck”)

What I should have realized was that once fermentation really got revved up, it no longer needed the extra temperature boost from those heating pads.

I was about to violate lesson #2 about keeping interventions to a minimum.

And when I awoke the next morning, the must temperature was at 94˚!!

Too much heat!!!!

I immediately removed the heating pads (good decision), and within 8 hours the temperature dropped to 88˚.

In retrospect, what I should have done upon awakening to find my must temperature at 94˚ was to be more proactive and reduce the temperature more rapidly by placing plastic frozen water jugs into the hot must. In essence, because I had over-indulged my intervention of heating, I should have been more proactive in more readily correcting that mistake. If I was making my wine at a high-class commercial winery I would be able to use huge fermenting containers that were temperature controlled and would have automatically kept the fermentation temperature of the must in the proper range (one of the many drawbacks to not being a multi-millionnaire).

Did this temperature SNAFU impact the final wine, you ask?

Fast forward to Piero Spada, one of our WVA professional winemakers, who told me (after extensive prodding on my part) that he detected a barely perceptible off-flavor in this wine that may have been caused by the must being “over-cooked”. So one lesson is to learn from your mistakes. For you home winemakers out there, you should insist that those who taste your wine give you honest feedback, especially if they are highly knowledgeable. Do not shy away from criticism; learn from it!

Fermentation: “Punching Down the Cap”

Throughout this fermentation period I was “punching down my must cap” three times a day.

Let me state right now that punching down the cap is a lot of fun! But what is “the cap” you ask?


Let me state, punching down a cap is a lot of fun for people of all ages

As previously mentioned, as the yeast consumes the sugar in your crushed grapes, it turns that sugar into alcohol and carbon dioxide, and that carbon dioxide literally pushes the grape skins up from the must liquid to the surface, forming this cool-looking “cap” that will impress anyone who witnesses it. You could organize an entire dinner party around people observing this must cap! Really, I have invited people over to my house just so that I could show them this cap, and they all left impressed (or at least that is the story I choose to relate here). 

In fact, the cap gets sufficiently hard that you can rest a glass of wine on top of it to further impress your friends (see photo at the end of this post to see that I do indeed employ this attention-seeking technique). After two days, when the S.G. was at 1.030, I added 30 grams of Fermaid K, which is a complex formula of amino acids, unsaturated fatty acids, vitamins, & other micronutrients to maintain yeast alcohol resistance and keep volatile acidity levels low.

You should not be too forceful when conducting punch downs, because you do not want to crush the grape seeds and release those harsh tannins inside the seeds into your fermenting wine; it will cause your wine to have an unpleasant and harsh bitter taste, similar to sucking on a wet tea bag.

A winemaker needs to be gentle.

As the fermentation nears its end, the integrity of the must cap will deteriorate, meaning it will become softer and mushier and not reform as quickly after each punch down. This is a sign that the yeast is close to finishing its consumption of sugar in the must and that you are not too far away from pressing (unless you are a fan of extended maceration, which is something we can discuss in a later post). 

When S.G. dropped to 1.010, I added 4 grams of Bacchus malolactic bacteria as well as 25 mg Acti-ML, which is a malolactic nutrient consisting of a blend of inactive yeasts rich in amino acids, mineral cofactors and vitamins which help keep the bacteria in suspension and strengthen it. By adding malolactic bacteria I was inducing malolactic fermentation in this very young wine.

What is malolactic fermentation? It is a “secondary” fermentation process often induced by winemakers (mostly in red winemaking), in which malolactic bacteria is added to the just-fermented wine, converting the tart-tasting malic acid, naturally present in grape must, into softer-tasting lactic acid (think “buttery” taste). Most dry red wines go through malolactic fermentation, as do some white wines, such as chardonnay.

Pressing and Sur Lie

I continued to (gently) punch down my must for a total of 6 days. When the new wine reached a S.G. of 1.000, meaning there was only a little bit of sugar left in the must, it was time to press.

This is my press (see photos below), stored on my front porch. It’s a fun tool and I bought it from an antique store, replaced a couple of the oak staves making up the basket, and it was then ready for service.

Over a five-hour time span, I pressed the fermented grape skins so that virtually all the new wine juice was squeezed out and flowed into waiting buckets, leaving behind the compressed remains of the grape skins, which is called the “pomace.” I filled 29 gallons of glass carboys with the new wine. After two days, when the new wine was fermented to dryness, I racked it off its “gross lees”, which is thick sediment at the bottom of the carboys that contain dead yeast, grape skin residue, and a few seeds. This second racking yielded 27 gallons of wine, a loss of two gallons due to the gross lees. Over the course of the next few weeks, I periodically stirred this new wine in the glass carboys, causing the now silky “fine lees” at the bottom to rise up in the wine and release their compounds. This process of allowing the new wine to lie on top of the fine lees and to periodically stir the fine lees up into the wine is called the Sur Lie (pronounced “Surly”) aging process, which in French literally means “on the lees.” Unlike the gross lees, which contain harmful compounds that can ruin your wine, fine lees contain dead yeast cells and proteins that smooth out and add desirable flavors to the wine, and can also result in a creamier, more viscous mouthfeel.


About five weeks after fermentation had begun, the wine’s pH was at 3.70 and malolactic fermentation was complete.

Cold Stabilization

Tartrate crystals are formed in wine when tartaric acid binds with potassium (two natural components in all wine) due to the wine being sufficiently chilled for a period of time. These crystals do not form in unfermented grape juice because they are more soluble (capable of being dissolved) in the unfermented juice. To encourage the precipitation (formation) of tartrate crystals in the wine, a winemaker engages in what is called cold stabilization. Tartrate crystals are those small little glasslike slush that you may (or may not) have seen at the bottom of your wine glass when you pour out the last bit of wine from the bottle. Commercial winemakers are very dedicated to cold stabilization, and therefore, remove these tartrate crystals before their wine goes to market. However,  many “rustic European” varieties do not remove the tartrate crystals prior to bottling, perhaps to retain a sense of authenticity, or perhaps due to laziness. Tartrate crystals don’t affect the taste of the wine, just the sight of that last glassful. Most people today like their wines to be clean and “glasslike-slush-at-the-bottom-of-the-glass”-free. So to meet those standards, I also cold stabilized by placing each of the carboys into my garage refrigerator for about two weeks. The result was a drop-out of tartrate crystals. I should end this discussion of tartrate crystals by stating that some people who love “Old World” (European) wines actually seek out the bottles with visible crystals because they view their presence as a sign of quality, believing it indicates that the wine has not been robbed of its structure through unnatural chilling. They lovingly refer to these crystals as “wine diamonds.” I don’t necessarily believe that tartrate crystals indicate quality (I’ve tasted my share of mediocre wine with the “diamonds”), but I certainly am not fazed when I see these crystals in a wine bottle.

After racking off the wine from the tartrate crystals that had formed a crust over the fine lees at the bottom of each carboy, I sulfited the wine by adding ¼ teaspoon of potassium metabisulphite to each five-gallon carboy. This chemical is an antioxidant that helps to preserve the wine; virtually all winemakers use this chemical and those that don’t risk ruined wine.

For those of you interested in the science part, the pH level was still at 3.70, which was a bit surprising given that at least some tartrate crystals had been removed, which I thought would have raised the pH level a bit due to acid levels dropping. A pH level of 3.70 is at the upper limit; any higher and the wine becomes vulnerable to spoilage, but it is still in the acceptable range.

Barrel Aging (Mostly)

Within two weeks I racked the wine into a 20-gallon white-oak barrel, a 6-gallon carboy, and a 2-liter bottle.

After aging the wine for four months, I added 1.00 tsp potassium metabisulphite to the 20-gallon barrel and a ¼ teaspoon to the 6-gallon carboy.

After the fifth month, a taste test found the wine to be moderately tannic, jammy, with a deep dark purple-red color and a pH = 3.70.

At the eighth month, it had a nice fruity aroma, and was very tannic and moderately acidic.

After an additional seven months (total of fifteen months), I added another ¾ teaspoon of potassium metabisulphite to the barrel.

At the sixteenth month, a taste test found the wine to have a deep dark purple-red color, nice earthy aroma, plummy, full-bodied taste, with both moderate tannins and acidity.


After 16 months in barrel I racked the wine into carboys, adding ¼ teaspoon of potassium metabisulphite for every five gallons and then bottled. The alcohol level was at about 13%, and pH = 3.61. The wine tasted very good, but still needed to be bottle aged; it will continue to mature in the bottle for at least the next five years, but probably longer. Refrain from drinking newly bottled wine for 30 days (I know that might be difficult!) to allow the wine to overcome “bottle shock,” which is the sometimes off-taste or “off-look” of newly bottled wine, presumably caused by the bottling process.

For those still following the science part, do you wonder why the pH had dropped rather than risen?

Well, I’m actually guessing that this anomaly was because of the unreliability of my three-year old pH meter! … I have since purchased a new meter and now conduct two separate pH tests using these two meters. Thus, the last lesson I would like to pass along is to maintain the quality of your winemaking equipment.


The stages of winemaking

While this may have been more detailed than you anticipated, I hope it helped lay the ground for our further discovery of wine and our learning process of the transformative elements of winemaking.

6 thoughts on “But getting down to it, how is wine made?

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