Winemaking 101 – Part II: Fermentation — Crafting the “Juice”

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The Juice

We explored how wine is grown in our last discussion. Now we’ll explore how those gorgeous bunches of grapes turn from orbs of promise to barrels of wine. From red to white, sparkling to fortified, winemaking follows a fascinating process of craft and chemistry that mankind began refining in ancient times. Thanks to modern science, we understand what and how fresh grapes turn into complex wines.

The first lesson you learn studying wine is that while there are infinite ways to fine tune your wine, there is only one basic method to vinify grapes. What’s that? Fermentation.

The process of fermentation, as written in chemical notation, looks like this:

C6 H12 O6 + 6O2 6CO2 + 6H2 O

Not exactly romantic, is it? Not to worry, we’re getting to the good stuff very quickly. But before we do, take a long look at the arrow in the middle of the equation. That arrow owes its very existence to single celled organisms called yeast. These gluttonous little fungi gorge on sugar naturally found in ripe grapes and convert it into ethanol (alcohol) and carbon dioxide (bubbles). The results range from the deepest purple-black glassfuls to ethereal goblets of golden bubbles. Yeast: we salut you.

The Light and The Dark – Production of White and Red Wine

The short form version of winemaking: white wines emerge from the cellar ranging from pale, watery white to deep, golden yellow. Red wine has a few more steps and variations. Steps for white wine are noted as W. Steps for Red Wine are noted as R. Once your harvested grapes arrive at your winery, the basic process looks like this:

W&R – Sorting – you’ll want to sort grapes to dispose of leaves, less than ideal grapes, bugs and anything else that is best kept out of your wine.

W&R – Crush & Destemming – you may select from an assortment of methods, but you will want to gently break the skins and remove the woody stems from your grapes. Breaking the skins gets the juice flowing and ensures that you don’t have more stemmy goodness in your wine than you want.

Winemaking 101 - Sorting, Destemming, Crushing | How to Make Wine

It’s fairly common for sorting (metal slides at the top of the image), destemming, crushing and placement into a vessel (stacked mid image) all to happen in rapid succession.

R – Maceration – The origin of red wine’s color lies right here. Red grape skins harbor plant based compounds that lend color, flavor, structure, and the often mentioned tannin to wine. While these compounds exist in white grape skins, they don’t play the same center-stage role in the wine. That said, maceration is the time that the juice from the red grapes spend on their skins. Like making tea, the more time spent on the skins, the more color and flavor is extracted.

W&R – Free Run & Press – the sheer weight of your grapes lets gravity do some of the work in coaxing the juice from the grape for your wine. But, if that’s not quite enough pre-wine or you want some more heft, pressing that grapey mass will give some more to work with.

W&R – Pre-fermentation options – you can chill your wine to keep it from losing its fresh aromas; settleand rack it to allow a portion of the grape solids to fall to the bottom of your tank and pump your wine into a new vessel leaving that sediment behind; clarify it to remove unwanted elements like solids, bacteria, and the like; and lastly, you can opt for a culture of yeast if you’re so inclined.

W&R – Vessel – Now you get to select what sort of fermentation vessel you want to use. Options include new oak, used or neutral oak, cement, and stainless steel. This selection will impact the final flavor profile of your wine, so go wild!

Winemaking 101 - Steel barrels vs. French Oak.

A couple of options for vessels used in winemaking — Steel barrels vs. French Oak.

W&R – Fermentation (Yay!) – Now we’re getting somewhere! If you haven’t added a cultured yeast, then the ambient yeast in the air of your winery will get the party started. Yeast come in different strains to achieve different effects, but rest assured that pretty much all of them will ferment your wine.

R – Maceration – Just like before, this is a moment to extract more color and flavor goodness from your grape skins.

Winemaking 101 - Fermentation & Maceration can take place in larger tanks before moving the wine to smaller aging vessels.

Maceration can take place in larger tanks before moving the wine to smaller aging vessels.

R&W (Optional) – Malolactic Fermentation (MLF) – Such a long phrase for a rather simple process. The MLF (ML, or malo, depending on your wine geek) process is the addition of lactic acid bacteria (naturally occurring in most wineries). These bacteria convert malic acid (like that found in green apples) into lactic acid (like that found in butter), thus softening the acidity of the wine and creating a buttery or creamy flavor. See? No chemical notation. Easy peesy.

R&W (Optional) – Lees contact or stirring – You may recall that we discussed this before, but there’s no time like the present to review. Lees are the spent yeast and grape materials that form a sediment after fermentation. As the yeast cells break down, they lend flavors and aromas of freshly baked goods to the resulting wine. Totally optional, and more common in some wines than others.

R&W – Racking – You may have opted to do before fermentation too, but this time it takes on a whole new importance. Most of the time this looks like putting a hose into one of your vessel, pumping the wine off of its lees and silt, and settling it into a fresh, clean vessel. You can do this as much or as little as you like, until you’re pleased with the clarity of your wine.

R&W – Blending – Let’s say that your fruit came from distinct vineyards OR that you’ve got several different grapes. You may have fermented each independently, in its own private vessel. Now that you’ve gotten some wine made, you can blend your plots to achieve the perfect taste. Fifty-fifty to 90:10, it’s your artistry.

Aging wine in Oak Barrels after Fermentation - Winemaking 101

Wine, once fermented, can rest in barrel for quite some time before the final blend is set.

R&W – Stabilization, fining, filtering– Fine tuning before the big show. Stabilization makes sure that your wine isn’t going to put on any side shows, like throwing off extra sediment or tartaric acid crystals. Fining takes place in your vessel and means that you can drop your choice of material into the wine for the material to collect unwanted particles. And filtering is the last gatekeeper before you bottle your wine. It is exactly what it sounds like, and you’ll pump your wine through specific filters to remove specific elements of materials.

R&W – Bottling – You grew your grapes, you made your wine, and hopefully you’ve picked out some very nice bottles and closures. The bottling line is your finish line…or is it?

Bottling Wine After Fermentation and Aging - The Bottling Line in the Winery

The subtle glory of the bottling line.

R&W – Bottle Aging – Okay, one last little thing. Wine is glorious bottled chemistry, and that chemistry doesn’t stop once your wine gets into your bottle. The chemical compounds from the grapes and winemaking process will continue to evolve in the bottle, combining to form larger molecules which will change the texture and flavors of your wine.

Barrel cat, Oscar. Loud, fat, annoying, but apparently a great mouser.

The usual suspects in your cellar include: wine you’d like to finish making, a dedicated cellar cat, and a pesky writer tasting the wine you’d like to finish making.

Ahhh…the remarkable flavors of success. Sparkling, sweet, and fortified wines each have their own special variation on this process. But that’s a discussion for another day! Next, we’ll take a look into the vineyard, the cellar, or the tasting room for experience and exposure.

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Maisie Lyman
Maisie Lyman
WSET III Sommelier at Fruition Sciences
Wanderlust lured Maisie from a comfortable career in commercial land developement in 2008. She jumped corporate ship and started studying one of makind's largest and most ancient fascinations: wine growing.

She's WSET III certified and splits her time between technical writing for Fruition Sciences (dirt and vines) and flavorful writing for Good Company Wines (globe trotting by the glassful). Her studies at UC Davis, the Napa Valley Wine Academy, and elsewhere ensure that what she doesn't know, she will soon find out.
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Wanderlust lured Maisie from a comfortable career in commercial land developement in 2008. She jumped corporate ship and started studying one of makind's largest and most ancient fascinations: wine growing. She's WSET III certified and splits her time between technical writing for Fruition Sciences (dirt and vines) and flavorful writing for Good Company Wines (globe trotting by the glassful). Her studies at UC Davis, the Napa Valley Wine Academy, and elsewhere ensure that what she doesn't know, she will soon find out.


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