Fermentation Tanks

July 27, 2021

Outdoor Fermentation Tanks vs. Alfresco Fermentation

An interesting movement has arisen within the U.S. wine making industry. A small number of vintners, choosing to get back to what they consider old-school ways, are abandoning the idea of fermenting in temperature-controlled tanks. Instead, they are practicing alfresco fermentation. This is to say that they are fermenting their wine in outdoor vats without the benefit of forced temperature control.

Of course, this defies thousands of years of wine making. Even breweries gave up alfresco fermentation with the development of concrete brewing facilities. So why are some smaller vintners sold on the alfresco fermentation idea? They say it gives them a better product.

Temperature-Controlled Fermentation

It should be noted that temperature-controlled fermentation tanks are rooted in generations of wine making and brewing. Modern fermentation tanks are chilled with a glycol panel. They are constantly monitored to maintain the desired temperature. Outdoor fermentation tanks are harder to control for obvious reasons, but some operations see benefits to keeping fermentation outdoors.

Thousands of years ago, winemakers were digging holes to create underground wine cellars where they could keep their precious grapes cool. They eventually began using concrete to build stronger wine cellars that were easier to control. It was all an attempt to prevent heat spikes.

These days, the vast majority of winemakers and breweries still depend on temperature-controlled fermentation tanks. They do not like leaving fermentation to nature. And yet, the alfresco fermentation method is alive and well.

Fermenting in the Field

Alfresco fermentation is more a product of wine making than beer brewing. Wineries choosing this method leave their grapes in huge vats right out in the field. They allow nature to take its course despite subjecting the grapes to warmer days and cooler nights.

It has been said that alfresco fermentation is like using a slow cooker. Think of a Dutch oven or crock pot. You put the food in and let it slow cook all day. For some people, this is the only way to prepare meals. They say that slow cooking offers the most nutritional value and preserves more flavor.

Vintners say the same principle applies to alfresco fermentation. They say they don’t get the spikes that vintners utilizing temperature-controlled fermentation tanks have to work so hard to avoid. If this is true, it is likely because temperature changes occur quite gradually in the natural world.

A given locale may experience a temperature difference of 10-20 degrees during a single 24-hour period. However, temperatures gradually increase during the day before gradually falling at night. Vintners say that gradual temperature changes not only do not harm the grapes, but they actually make for a better fermentation process.

Fermenting at Scale

One of the big downsides to alfresco fermenting is the difficulty of doing it at scale. Perhaps that’s why it is a practice limited mainly to small wineries and craft breweries. Producing large volumes of product requires consistency. And that means tighter control from start to finish.

Control is what you get when you ferment in larger stainless-steel tanks with built-in cooling. You get precise temperature control that leaves nothing to chance. For some vintners and brewers, such control is non-negotiable.

Are you in the market for new fermentation tanks? If so, we invite you to take a look at our inventory. Our stainless-steel tanks meet or exceed all regulations and standards. They promise years of reliable service whether you choose indoor or outdoor fermentation. If you have chosen to attempt outdoor alfresco fermentation, we still might be able to help. Contact us to learn more about all of our tank solutions.

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