WHERE THE MAGIC HAPPENS: Fermentation And Storage Tanks

By Gerald Dlubala

The style and type of fermentation and storage tanks used in wineries are dependent on many factors, but always includes the winemaker’s beliefs, experiences and history regarding the quality and traits of the wine they want to produce. Tank suppliers have become true partners with wine producers, shouldering the trust and responsibility for providing quality vessels to ferment, hold and enhance the winemaker’s product while sometimes even providing insight on the proper use of their chosen vessel.

Terracotta Amphorae

Such is the case with Manu Fiorentini, Founder and CEO of Itek Wines, a tank supplier, distributor and filtration service provider servicing California’s Central Coast.

Itek Wines’ offerings include oak barrels from the French region of Burgundy, Italian concrete tanks from Nico Velo and a complete line of stainless-steel processing equipment for wine production. However, it may be Fiorentini’s line of Terracotta Amphorae fermenters that may be their most intriguing line of fermentation and aging tanks.

“Terracotta and clay are where it all started, used as the primary vessel to ferment, store and carry wine as far back as the Roman Empire,” says Fiorentini. “The actual reasons that terracotta fell out of favor have never really been identified. We don’t know if they had to stop using terracotta for a specific reason or they just found other means, but about fifteen or twenty years ago, there was a bit of a resurgence in using terracotta and other clays for the purpose of fermenting and storing wines.”

Itek carries terracotta amphorae crafted from the renowned Impruneta clay, a unique blend of natural ingredients found in Tuscany and made by what he calls “local mom-and-pop producers.”

“There hasn’t been a whole lot of modifications to the vessel itself, just different mixtures of clay to control porosity without excess leakage. That porosity allows for natural micro-oxygenation which is beneficial for a healthy fermentation and bonding anthocyanin for better color in red wines. Additionally, amphorae are thin-walled, measuring only about an inch thick. This allows the amphora to sweat, eliminating excess wetness without adding in any strong tannins or aromas like oak,” says Fiorentini. “[These fermenters] are crafted primarily of minerals similar to those that are found in actual vineyard soil. The grapevines have been feeding off these types of soil-based minerals their entire lifespan, so continuing with fermentation and storage in that same, neutral environment allows for full expressions of flavor and minerality of the grapes, whether red or white. The results are very smooth tasting wines, with a soft, almost plush, pulpy mouthfeel, sometimes featuring a very slight mineral or earthy tone. It’s a happy result that has carried through even within our blending experiments.”

The benefits of this vessel extend to temperature control as well. “Terracotta amphorae also possess an extraordinary thermal insulation capacity that keeps contents cool by evaporating excess heat. The fermentation is slightly slower than you may be used to in other materials, staying steady and without heat spikes. Amphorae work for both wine and beer, providing a richer and brighter mouthfeel for either,” said Fiorentini.

Maintenance on amphorae is minimal. “They need, for now, to be washed with hot water at one hundred twenty degrees or less, due to the expansion possibilities of attached stainless hardware. That expansion can put pressure on the clay and possibly cause cracking,” Fiorentini told The Grapevine Magazine. “With our newer models, the stainless accessories are no longer attached to an embedded framework, so this is no longer an issue. You can use chemicals to clean and sanitize if needed, and then later to neutralize, but the amphorae are light and durable enough to tilt or lay flat for total access and superior drainage. Some wine producers have lined the interior of the amphorae with organic beeswax. This affects the oxygenation rates, and is usually done only with white wine varietals.”

Terracotta tanks have demonstrated superior lifespans when cared for properly, with some original vessels documented at over one hundred years old. The newer versions have been around for twenty years with little to no issues, and are rated comparable to concrete for longevity. If small, hairline cracks ever do show up, food grade resins, the same ones used for concrete tank repair, are perfect for correcting the cracking. Itek adheres to a detailed, multiple point inspection process from shipment to delivery, and the terracotta amphorae can be installed on powder coated frames if desired, making them easier to move and set in place with forklifts.

Tim Mondavi, American wine royalty and winegrower and proprietor at Continuum Estates, appreciates this type of vessel. “Concrete or various types of earth or clay are among the oldest containers known to man and among the oldest used for wine. They develop more elegance and tenderness of texture,” he says.

Rocking The Concrete

Concrete tanks remain a preferred choice for fermentation in many progressive wineries. Some of the most renowned wines in the world, including Château Petrus in Pomerol and Cheval Blanc in Saint-Émilion currently rely on concrete to produce their wines.

Experienced residential and business concrete companies like Sonoma Cast Stone of Petaluma, California have seen a resurgence in concrete use within wineries, designing and building concrete fermentation and holding tanks throughout Napa and Sonoma.

For wineries desiring a custom built concrete fermentation tank, casting the first mold comes with certain upfront costs. However, concrete is a balanced compromise between nonporous stainless steel and flavor-imparting oak barrels. Like clay, concrete allows a slower exchange of oxygen, and because of the tank’s massive size, temperatures rise slowly and steadily, eliminating heat spikes. Concrete fermentation tanks don’t require the cooling that stainless tanks need, so fermentation happens more naturally, resulting in better textures and aromatic notes. Like oak, but on a much smaller scale, concrete tanks retain a small amount of yeast and other natural byproducts from previous uses that impart additional qualities during future fermentations.

Applying epoxy coatings to concrete tanks may stop surface erosion caused by acidity in fermenting wines, but while epoxy covered tanks make cleaning and maintenance easier, some winemakers reported issues with temperature control and oxygenation. About ten years ago, this led some concrete tank manufacturers, including Nico Velo in Italy, to go back to using concrete without epoxy. However, they created new formulas, using concrete mixtures far superior to old ones, with no lime, silica, or other toxins typically used in standard, structural concrete. Manufacturers prep these modern concrete tanks with high acidic treatments to create a natural barrier that stops wine penetrating the concrete walls. Temperature control plates equipped inside tank walls provide slow, consistent temperature changes.

Tank shape can be custom molded and designed to fit any available space. Egg-shape tanks are popular since they lack corners or pockets for fermenting liquids to settle and stagnate. Other options include cubes and tulips, as well as round, cylindrical and custom shapes, limited only by the imagination. Customers install concrete tanks above ground, buried into the earth for thermal regulation, or even integrate them into the structural engineering of their building. Glycol temperature control systems can be embedded into the walls of concrete tanks, keeping them out of direct contact with the wine and preventing hot and cold spots.

Wood is Still Good

With all this talk about clay and concrete, for many vintners wood has not yet lost its charm or usefulness. Oak casks and vats offer quality holding power while providing outstanding and significant aromatic results. Even better, wooden vessels can now be fitted with many of the same convenience options that stainless-steel tanks offer, including the crawl-through doors, sash doors, top hatches, easily accessible drainage pipes, temperature control plates, thermometers and leveling gauges.

Red grape varietals are regularly housed in wooden vessels during early fermentation. Cabernet Sauvignon varietals are especially receptive to French oak barrels, readily accepting the familiar nose, tannins and vanilla flavors that we have come to expect. Bordeaux and Burgundy cooperages also use mainly French oak. Pinot Noirs and other lighter wines of the Pacific Northwest age exceptionally well in oak casks. Winemaker Chris Cooney of Dana Estates in Napa Valley says that wood tanks provide the great insulation that moderates the speed of temperature during the early fermentation process, allowing for smoother texture with less astringent properties.

Stainless For A Modern World

When it comes to cleaning, sanitation and maintenance, vintners are always looking for a better, more efficient way. It was partially because of this that stainless-steel tanks in wineries became the norm. Stainless steel is easy to clean and sanitize by hand or through a clean-in-place system. Also, their size is customizable, they can be modified to maintain proper temperatures easily, and they’re lightweight, making shipping and tank mobility simpler. These benefits, according to Colin Laursen, International Sales Manager for Paul Mueller Company, make stainless the best option.

“Presently, within wine production, we largely focus on stainless steel fermentation vessels because other than routine cleaning, there is very little regular maintenance required on a stainless-steel tank,” says Laursen. “Over time, the gaskets will need to be replaced, and if you use a tank with an agitator, some moving parts will need service, but honestly, I’ve seen our tanks currently in the field that we built back in the 1960s. Our tanks are known for their longevity.”

With global partners including Kendall-Jackson, Beringer, E & J Gallo and others, the Paul Mueller Company is no rookie when it comes to providing top quality, stainless steel tanks for the winery business. They offer standard tanks in different sizes but are also able to accommodate the individual needs of a winery when needed.

“The different red and white wine varietals won’t usually require different style tanks, but once you move into sparkling wines, you need different design specifications and considerations to produce a tank that can maintain high internal pressure,” Laursen says. “We also make stainless steel wine barrels to provide solutions for those winemakers looking for flexibility in their storage and fermentation choices.”

The simplicity of the stainless steel tank design makes improvements on it unlikely at this stage but opens the door for innovations in cleaning and maintenance. “Most of the trends we see coming aren’t about the tanks themselves, but rather in tank cleaning improvements and product agitation and recirculation,” says Laursen.

Laursen believes that stainless steel tanks are here to stay, with no new type of storage or fermentation vessel unseating them any time soon. “Tanks such as wood and concrete can have their place within the winery. The winemaker’s process will dictate tank requirements … but stainless is really the way to go.”

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