Updated: Jun 16, 2020
Without primary fermentation, we would not have wine. Primary fermentation generally refers to the stage of winemaking when the yeast is converting the sugars to alcohol and CO2. This stage can last from about one to three weeks. What happens at primary fermentation doesn’t stay at primary fermentation though. The decisions made during this period can have a major impact on the final characteristics of the wine.
For traditional red winemaking, the grape skins remain in contact with the juice during primary fermentation. For white winemaking, the juice is pressed off the skins as soon as possible after harvesting and the juice fermented without skin or seed contact. It is more important to limit oxygen contact to a white wine during primary fermentation due to it’s lower tannin content and delicate flavors. Many home winemakers will make red wine from flash extracted juice or concentrate, so the process can have more parallels to white wine than traditional red wine. These process differences lead to different requirements in the actual primary fermenter.
A primary fermenter does not need to be fancy or expensive, but does need to accommodate the style and the volume of wine that you will be fermenting. The most important characteristics of a primary fermenter are type (open top, closed top, sealed, mechanized), volume, height to diameter ratio, material, and ease of use. There is no one-size-fits-all fermenter, so it is up to the winemaker to best decide what to use for this critical stage of the winemaking. In this article we will go over some of the options that you may choose to use, as well as the wine styles that they are typically used for.
Common Fermenter Options
Food Grade Bucket
Styles: Red, White, Rosé, Fruit
This is probably the most common primary fermenter for low volume home winemakers. A food grade bucket is inexpensive and generally comes with a sealable lid and a vent making it a versatile option. The most common sizes are six and seven gallons. The height to diameter ratio is around 2:1 which is preferred by many red winemakers. With a slightly taller height than diameter, more of of the cap will stay submerged between punch downs and the surface sees less air exposure than a shorter, wider fermenter.
The wine can be fermented with a towel covering the bucket, a loose lid, or a snapped down lid with vent depending on the type of wine you are making. A bucket also allows for easy punch downs of red wine. Punch downs can be achieved with a long serving spoon or small punch down tool. The food grade bucket is my favorite option as a home winemaker, as it allows me to make many smaller batches of wine rather than going all-in on less, larger batches.
Carboy or Demijohn
Styles: White, Rosé
This is a great option for white or rose wines, and you probably already have several laying around. Generally you will want to only fill these around 80% during the early stages of primary fermentation or you could experience unpleasant wine volcanos. During the early stages of fermentation I will place a clean rag over the opening, allowing a bit of air to the wine to promote a healthy yeast fermentation. As the fermentation slows down, I will replace the rag with an airlock. Towards the end of the fermentation, be sure to stir up the lees once every day or two to help prevent hydrogen sulfide and other reductive characteristics. After fermentation is complete, rack the wine off of the thick lees, into a clean carboy and top-up to the neck. The wine is much more susceptible to oxidation after fermentation is complete so it is important to keep an airlock or solid bung on after things settle down.
Food Grade Plastic or Stainless Steel Barrel
A food grade or stainless steel barrel is much like a bucket, only larger. These work great for red wines, allowing easy punch downs and a good height to diameter ratio. To keep fruit flies out, I like to cover with a large towel. Towards the end of fermentation as the CO2 blanket weakens, the towel can be replaced with a sheet of rigid plastic or a loose lid if you have one. 50-60 gallon barrels are great for small winemaking clubs or home winemakers that want to scale up a bit.
Another similar option are food grade trash cans. These are available 10 to 40 gallon sizes and are generally offered with lids to keep the fruit flies out.
Speidel Plastic Fermenter
Styles: Red, White, Rosé, Fruit
Speidel is known in the wine industry for large commercial grade stainless tanks and fermenters. They now offer smaller plastic fermenters for home winemakers and brewers. The advantage to of these over a plastic barrel is that they offer a sealable lid with an optional airlock and a spout for draining. The ability to seal the lid makes them also useful for short term wine storage or aging. I use a 15.9 gal speidel fermenter for smaller batches when possible. The work required to punch down one larger fermenter is about the same as one smaller bucket and at 15.9 gallons it is still not too bad to move around.
Variable Volume Fermenter
Styles: Red, White, Rosé, Fruit
This is much like a stainless barrel, but it contains a lid that can be lowered or lifted, then sealed with an inflatable bike tube style seal. The ability to minimize the headspace allows this fermenter to be used for white wines and for short term wine storage or aging.
Oak Barrel with Head Removed
Styles: Red, White
Red wines can be “barrel fermented” in oak wine barrels with the heads removed. There are some benefits to oak contact during fermentation, and of course “barrel fermented” sounds cool. You can achieve much of the same benefit with oak alternatives such as cubes or staves in an easier to work with stainless or plastic fermenter, so I generally would not recommend this option.
White wines like Chardonnay can also be barrel fermented but without removing the barrel head. This is a little more practical than fermenting a red wine in barrel. Wines fermented with oak can develop a more complex tannin structure and reduced vegetal flavors.
These are the ultimate in open top fermentation and offer the ability to be fork lifted around in winery. A macro bin is a square plastic tub on a pallet like base. One macro bin can generally hold enough must to make 2-4 barrels of wine depending on the size. These are commonly found in small to medium sized California wineries. Macro bins can be stacked when space is tight.
Closed Top ("Sealed") Stainless Tank
Styles: White, Rosé, Fruit
Closed top tanks are generally used for white wine fermentations and red or white wine storage. These tanks allow venting without excess oxygen exposure. Occasionally these tanks are equipped with a conical bottom to allow easy removal of the lees after fermentation. At large wineries, you will often see rows of sealed stainless tanks.
Stainless Tank with Manway and Pump Over System:
Some of the more modern red wine fermenters at large wineries are equipped with a pump over system and a manway on top for monitoring and access. These tanks are essentially closed top fermenters with more features to allow the fermentation of a red wine with grape skins, pulp and seeds. The pump over system takes wine from the bottom of the tank and sprinkles it over the skins with the help of a must pump. This achieves much of the benefit of a punch down but in a gentler and more convenient way.
Jacketed Stainless Tanks
Styles: White, Red, Rosé
These tanks are much like a standard sealed tank, but feature a liquid coolant layer between the wine and the outside environment. This allows the inside temperature to be controlled during fermentation or storage. These are beneficial if the goal is to make a fruit forward wine and a cool, slow fermentation is intended. They can also be used to stall or crash a fermentation, leaving some residual sugar for a semi-sweet or sweet wine.
There are many styles tanks that can be used for primary wine fermentation, and while this article covers many of the most common options, it does not cover everything. Once you know the goals, budget, and wine volume, you can select an appropriate primary fermenter. In larger scale operations, it is very important to order the fermenters well in advance of the wine harvest since they are often made to order and can have lead times of many months. For us small winemakers at home, you generally get creative and find fermenters to suit your needs in short notice.
For more winemaking tips, tricks, and information, be sure to check out my youtube channel. If you have more insights on primary fermenters, leave a comment! Cheers!
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