So far in Grape to Glass, we’ve covered picking the grapes and crushing them. Both of these steps are extremely important. If they’re rushed, mistimed, or done sloppily, the step we’re talking about with this piece, fermentation, would yield a liquid you’d want nothing to do with!

Yet, let’s face it, this is the step that fascinates us all, the step where the magic happens! And it truly is magical.

Fermentation occurs naturally, and has been around long before humans figured out how to harness it to craft alcoholic beverages. In fact, some scientists believe that we have a taste for alcohol in the first place because perfectly ripe fruit hanging on a tree has an alcohol content of around 2-3%.

The hypothesis, first proposed by Dr. Robert Dudley of the University of California at Berkeley, goes something like this. We have ancestors that could tell a fruit was ripe by the presence of alcohol, likely by smelling it on the air. They would risk life and limb to get it. Fruit that ripe would grow higher up in trees, where other animals couldn’t get to it. Anyone that could get to it before it fell to the ground would have a feast, and get a nice buzz as a reward. Anyone that ate too much, though, might fall out of the tree!

The same basic process that happens in tree fruit happens in a winery: yeast eat the sugar from the fruit and convert it into carbon dioxide and alcohol. In a winery, however, winemakers control for things like temperature, types of yeast, length of fermentation, the amount of oxygen that hits the wine as it ferments, the vessel in which the fermentation happens, and so on.

Sugar to alcohol is not the only type of fermentation. A very common type, done to nearly all reds and some whites, is called “malolactic fermentation.” Here, after the initial fermentation that creates alcohol, a certain bacteria converts malic acid into lactic acid. This gives the wine a richer, fuller texture.

This process explains the difference between Chablis, a region of France that produces a crisp, green apple tasting version of Chardonnay, and examples from California that feel round on your palette and have more tropical fruit notes. Malic acid is what gives green apples their tartness, and lactic acid occurs in milk and adds to its creamy texture.

The decisions that a winemaker makes during fermentation have profound effects on the resulting wine. Ferment a red wine for too long, you run the risk of pulling too many tannins into the solution. Too short, and the wine will lack structure and depth of flavor. Choose the wrong yeast, and the wine will have off flavors, or may not fully ferment, as only certain yeast can survive in the alcohol content of some modern wines (more than 13% alcohol).

Some decisions have become obvious as wine knowledge grows. If you want a crisp white, for instance, ferment in a stainless steel tank and keep as much oxygen out as you can. If you want a rich, fruity red that’s ready to drink after only a few years, pump the wine over constantly to introduce extra oxygen. If you want a super creamy Chardonnay with layers of butterscotch, ferment in stainless steel then age it in new French oak for at least a year.

As with any creative endeavor, sometimes breaking the rules, or making decisions contrary to tradition or convention, leads to amazing results. Why not barrel ferment a Riesling, or make a Touriga Nacional with no time spent in oak (we have one at the shop, and it’s incredible!)? While these experiments can lead to failures, sometimes they lead to stellar wines that change the convention they bucked in the first place.

To finish off this discussion of fermentation, we want to touch on a style of wine that we love at Grand Cata. Pipeño, made in southern Chile with mostly the grape País, manages to uphold local tradition while bucking modern conventional thinking. The results are a lean, slightly tannic wine with smoky and funky notes floating around deep berry flavors.

Pipeño literally means “from the Pipa.” A pipa is an open-topped beachwood tank - seriously, beechwood! Often on wheels so winemakers can move it closer to wherever the grapes are being crushed, the pipa is truly unique in the wine world. The closest thing to temperature control is to put the pipa in a barn. All the yeast comes from the grape skins, and whatever floats around. The goal is to ferment as quickly as possible so that harvesters of other crops and grapes have something to quench their thirst in the hot sun!

We hope this piece clears up some questions you had about fermentation! In our next installment, we will talk about a process that we actually touched on quite a bit in this piece, maceration. Maceration and fermentation often happen simultaneously, but is a concept all on its own that deserves attention. Stay tuned!


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