For those approaching the subject for the first time, there can be a bewildering array to choose from. Materials might include stainless steel, concrete, oak, plastic or even clay. Each comes with its own advantages, disadvantages and price tag. So how does one negotiate the tricky business of tank selection?
Tank selection
- Look at vineyard size and predicted production volumes. Not only do vessels need to be able to accommodate all of the juice produced at harvest, but consideration needs to be given as to how this will be divided up by style.
- This leads us on neatly to style and quality considerations. Different materials offer the potential for different outcomes at the end of the process. Stainless steel is perhaps the most common and relatively cost-effective material, leading to crisp, clean wines. Oak vessels come at a significant price but can add more complex layers of flavour to the finished product.
- For some winemakers, environmental impact and sustainability are at the heart of their working practices. For them, the environmental impact of their tanks – how they were produced, how energy efficient they are and how recyclable they will be at the end of their life – can be a critical factor in selection.
- I’ve alluded to the price already, but it isn’t just the upfront costs that need to be considered. Maintenance and the longevity of different tank types also need to be factored in so that an informed investment can be made that will keep the business in good shape over the years and decades to come.
A material question
Let’s look at some of the different types of tanks that are available in more detail. What do different materials add – or take away – from the finished wine?
Mixing materials
Stainless steel has become the industry standard. It’s an inert vessel, easy to keep clean and relatively affordable. But sometimes, a pure expression of the fruit isn’t all that’s required. Some winemakers look to add depth and complexity to their wines by blending liquid fermented in a range of materials.
In Hampshire, the Grange Estate’s Classic NV English Sparkling Wine is fermented 86% in stainless steel tanks and 14% in old oak barrels before undergoing a 33-month lees ageing process in bottle. The Grange Estate have recently moved into their own newly-built winery facility. Until 2022, their vinification took place at Hattingley Wine Estate, but now winemaker Harry Pickering has greater control over the vessels he sources and how he uses them to achieve the depth and complexity of flavour he is looking for.
“We ferment a bit of everything in barrel as well as in tanks. It gives you two different components to play with from the same fruit. For us, we find anywhere between 80% to 90% for the stainless steel tank fermentation is where things sit nicely.
“The tank components are the bones of the wine when we’re looking at blending, that’s the main structure. The fruit components are more obvious and it’s more structural in terms of acidity. By fermenting in tanks you get the pure expression of the fruit because they are in the most inert vessel and completely unadulterated.
“On top of that, you start to layer the oak. The majority of the oak we’ve used up until now is old oak, fourth fill. Those barrels come from a Tonnellerie in Champagne. They sell Champagne barrels to producers in Bordeaux and Burgundy. After they’ve had the yeast in them for four years fermenting white wines, they take them back and distribute them out to people who want older oak. The reason for going through this Tonnellerie is purely a reputational thing more than anything, in terms of knowing that the oak you’re going to get is being properly quality controlled. You’re trying to limit any spoilage or microbes being in that wood, so you need to know the provenance of the old oak to limit the risk of contamination.
“The idea is not to impart those oak tannins and give the wine an oakiness. It’s more about the micro oxygenation that you get from the oxygen being able to permeate through the wood during the ferment and ageing, compared to a stainless tank. In a barrel, there is a lot more surface area of the wine in contact with the yeast lees and the surface area of the barrel itself. That allows for more exposure to oxygen and more exposure to the dead yeast at the bottom of the barrel post fermentation. In turn, that leads to autolysis and the breakdown of the yeast. The mannoproteins that you’re getting from the dead yeast soften the wine and add those soft and buttery autolytic characters.
“So the old oak softens and it broadens the palate. That’s adding the flesh onto the bones. We find that between 10% and 20% in old oak is where that sits nicely. It’s about the balance between softening the wines, but still having them maintaining their structure and core personality. They’re not becoming overly flabby, just softening and rounding out the palate.
“Since we’ve had the winery, we are beginning to play a bit with new oak, which adds a third dimension to the whole thing – almost like the accessories that are added to clothing. But the amounts that we are adding are so tiny that you can barely perceive them. We only add about 1% to 5%. It ripens up the fruit and makes the wine a bit more serious. It’s almost like turning the volume up a bit. It’s not about changing it dramatically and making an oaky wine, it’s about adding a bit of perfume, that little bit of personality at the very end.
“Because this is a new thing for us, we’re still working out which Tonnellerie suits our needs. Each year we’re going to use a new one, look at their barrels and see how they work for us. Then we’ll hopefully end up with five or six different Tonnelleries’ barrels in the winery over the next few years, that are toasted to different degrees, and increase volumes depending on who we like most. I imagine it will always be a range of them because they will offer different things and it’s useful to have that diversity for blending.”
Clayver
Clayver produces oblong or spherical stoneware containers of various sizes used for the fermentation and refinement of wine.
It is becoming more common to see spherically shaped tanks, because this reduces the overall weight of the vessel and also encourages the natural convective movements within the liquid as it ferments. It also arguably has benefits when cleaning the vessel.
Clayvers have a very high firing temperature and are claimed to contain fewer metal ion contaminants than more established clayware containers. There is still a porous character to these tanks that allows a controlled amount of oxygen into the wine during ageing, but they are less porous than terracotta, for example.
Concrete
Concrete has been in use for fermentation for over a century, but fell out of favour as stainless steel became de rigueur. Concrete has the same inert qualities as stainless, but is also thermally consistent – taking a long time to heat up or cool down. This provides a stable environment for the yeast to slowly work its magic. This natural insulator is therefore also suitable for storing and ageing wines.
Unlike stainless tanks – and to some extent in common with wood – concrete tanks can impart a degree of flavour to the wine, a delicate mineral character. But primarily, it lets the fruit shine. No flavour is removed or masked by the vessel.
Concrete can be formed into virtually any size or shape. Square and rectangular tanks are quite common, but conical shapes are also possible. They can be built to order, to include valves, gauges and hatches wherever you should wish them to be placed.
Developing technologies
As vinification technology moves on, more advancements are being made in so-called smart tanks, which have sensors and automated controls to monitor and adjust temperature, pH and other variables in real time. An automated temperature regulation system might be used to control the temperature of the fermenting wine, reducing the risk of human error inherent in the monitoring of manual shut-off valves, for example.
Sonoma’s VinWizard was given an award for innovation in 2023 by the Wine Industry Network for their Multi-Sensor Probe (MSP). Building on the success of the Multi-Level Probe (MLP) which was released a decade ago, which measures the temperature of the entire tank, the MSP is able to provide real-time Brix measurements during fermentation. This is intended to overcome the inefficiencies that come with manual sampling, as well as the time it takes to gather multiple measurements throughout fermentation. The probe runs from the top to the bottom of the tank so provides multi-level Brix reading alongside the most accurate reading of temperature at the core of the tank without interfering with other mechanisms.
Having this data helps to visualise the fermentation that is occurring in each tank. It gives early warning if fermentation stalls. The technology can also be set up to work in combination with automation platforms to trigger various fermentation and winemaking processes if necessary – making adjustments to temperature or starting a pump over cycle, for example.
Research is also underway to automate microbial monitoring. Classical methods, like cultivation on plates, and even more recent technologies like flow cytometry can take a lot of time and not sample at the optimum frequency. The laboratory tests used an online flow cytometry system with a protocol for automating sampling, double-staining and analysis. The researchers assert that such technologies could be “particularly useful for facilitating and improving control of potential contaminants or stuck fermentations, as well as better piloting starter preparations, alcoholic fermentations, or malolactic fermentations.”
While the researchers are confident that their methodology shows promise, time will tell whether it can jump over the line into a commercially available solution that allows winemakers to monitor bacteria and yeasts over a long period of time and with high frequency testing that will provide a high resolution of data to the winemaker.
Of course, automation comes with a significant price tag. When considering the potential return on investment, it is important to look at the compatibility of new technologies with existing processes. There may be a technical skills gap within the workforce and proper training must be delivered so that automated solutions can be used properly and to the best advantage.
Ask an expert
Core Equipment have been supplying wineries in the UK for well over a decade. They can supply anything from a pump through to a press, to a full winery set up – covering the whole winemaking process. Vineyard magazine tapped into that expertise to find out more about some specific technologies that can assist in producing wine at the highest levels of quality.
Dan Tomlin from Core Equipment kindly shared his insights into some of the more interesting technologies on the market right now.
Fermentation control
As the UK wine market gains more expertise and winemaking know-how, fermentation control becomes more important to ensure the production of quality wines. Whether simply maintained at low temperature or regulated to allow for efficient fermentation, adding a temperature control system to winery tanks is essential.
Coolant supply can be discreet, provided by a network of stainless-steel pipework, pressure regulation systems, individual or centralised tank temperature control and remote access, to monitor the temperature. Core Equipment has installed over 25 full fermentation control systems across UK wineries and with this experience and technical knowledge of the fermentation process comes quality wine production.
Enhanced temperature control
Homogenous temperature is a critical detail of quality winemaking. A heated liquid is lighter than the same liquid at a lower temperature. With the heat source being located at the bottom of the tank, the convective flow will rise throughout the entire fluid and self-mix with the cooler fluid resulting in a very even temperature which couldn’t otherwise be achieved without mechanical mixing.
Letina INOX tanks, exclusively supplied by Core Equipment, can be made to suit any tank dimension, whether tall and narrow or wide and short, further enhancing the convective flow of liquid within the vessel. The rising warmer fluid leaves room for the cooler fluid which will take its place. This keeps the delta differential at its best level; reaching target temperatures more quickly.
With sustainability more relevant within the winemaking process, the result of faster and more accurate temperature control reduces energy consumption thus reducing the carbon footprint of the winery. Typically winery tanks are supplied with a simple cooling/heating jacket around the circumference of the tank, however, with the bespoke manufacturing process of Letina INOX tanks, jackets can be added to the underside of vessels, facilitating quicker temperature regulation and stabilisation process.
The positioning of these jackets ensures that temperature is being passed through the liquid, whereas with conventional tanks, we often see jackets simply heating the air within a tank. Heating a juice after cold settling, malolactic conversion allowing lees suspension, or of a red wine during alcoholic fermentation without overheating the cap are often key drivers to selecting this approach.
Compartment tanks
Compartment tanks, also known as multi-chamber tanks, are becoming more commonplace in UK wineries this type of winery tank allows winemakers flexibility when it comes to juice storage.
As yields vary from harvest to harvest, the compartments provide for the storage of different juice varieties without compromising on quality. The tanks optimise winery space, with often three or more compartments within one tank, meaning valuable floor space is not lost to rows of tanks. For the contract winemakers in the UK, this allows different varieties to be stored, settled and fermented in compartments designed to take smaller yields, where full tank space is not required.
