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Tuesday, April 23, 2013

Red Varietal Fermentation Vessels

The popular idiom "there's more than one way to skin a cat" is highly applicable to winemaking. The basics of winemaking are, well, basic, but I've seen and worked in many wineries; they all make wine, but all have different grape sources, different techniques, different wine styles, and different equipment, which means they all make highly differentiated end-products.

As we're just pushing through the last of our red ferments for vintage 2013 here at Vasse Felix, I thought this was a good opportunity to discuss what options winemakers have for red varietal fermentation. Winemakers here utilize three different vessels for red fermentations; omni bins, static fermentors, and rotary fermentors:
  • Bins - Picking bins are a common small ferment vessel in wineries. Here at Vasse Felix, we utilize omni bins, which are 1-ton picking bins. These are basically used like open-top fermentation tanks; they allow good access to the cap and gentle cap management with high extraction rates via punchdowns. They also have relatively high surface area to volume ratio, which increases juice contact with pomace (more extraction). The main downside of bin ferments is the lack of temperature control, which we try to mitigate by using a temperature-controlled cool room to try and keep ferment temperatures from rising too high (I've worked at other wineries that had cooling plates they could place in the bins directly). Winemakers here like using bin ferments for their particularly small batches of premium reds (less than 3 tons), and for batches they prefer to punchdown instead of pumpover. (below: me, punching down omni bins in Vasse Felix's cool room).
  • Static Fermentors - Vasse Felix have 5-ton and 8-ton stainless steel tanks purpose-built for red fermentation, including temperature control. They are not open-top tanks, but have larger top doors for access to the cap during pumpovers. These tanks have approximately a 1:3 surface area to volume ratio, smaller than the omni bins. Many wineries utilize static fermentors for red varietal fermentation because they can be used for a range of different wine processes (multi-purpose tanks are commonly used in this manner). Pumpovers are really the only method of cap management available for these tanks (besides delestage, or a 'rack and return', which is removing all juice/wine from the skins before pumping it back over the top) via a very gentle peristaltic pump (discussed in a following post) and manually hosed over the cap by cellarhands; this gives winemakers the option of non-aerative or aerative, and more extractive or less extractive (more vigorous or gentler). Their height and slope also allows cellarhands to dig out tanks through the bottom door directly into the basket press. Winemakers here use these tanks for the larger batches of premium reds. (Below: Vasse Felix's static red fermentors, you can also see the basket press in the left foreground).
  • Rotary Fermentors - Rotary fermentors are horizontally oriented (they lay on their side), which means they have very high surface area to volume ratio. This allows high rates of color and flavor that allow winemakers to press the wine off skins earlier in fermentation and avoid phenolic extraction. Rotary fermentors thus tend to producer rounder, fruit-driven wines that are approachable sooner than wines fermented in other vessels. Cap management is completed by rolling the tank (the tank sits on rollers and machinery rolls the entire tank), meaning very little manual labor is required. These tanks require a rather large amount of infrastructure and space - the rotary fermentors here at Vasse Felix range in size from 12-35 tons. Winemakers here use these tanks for our larger batches of reds. (below: rotary fermentors lined up along a tract that allows for draining directly into bladder press shown in the middle).
Of course, there are other options as well:
  • Open-Top Fermentors - Just as the name would suggest, these are tanks with no top. They usually have a similar surface area to volume ratio as static fermentors listed above, but the lack of a lid allows complete access to the cap and provides winemakers with the option of pumpovers or punchdowns for cap management. Vasse Felix has no open-top tanks at this stage, but several other wineries I have worked for utilized these extensively. Niven Family Wine Estates has the best of both worlds: stainless steel tanks with removable lids that allow tanks to convert from open-top fermentors to general-purpose tanks. (below: Niven Family Wine Estates tank room showing their range of 4-ton to 10-ton tanks, some with their lids on and some off. In the middle of the photograph, you can see the nuematic punchdown tool inside a tank, which is on a track to allow punchdowns of all tanks).
  • Oak Barrels and Tanks - It's standard to age red wine in oak, but there is a range of oak options for red varietal fermentation available today. Some wineries have begun removing one head of a new, 225-litre (60-gallon) barrel to use for on-skins ferments. They then press the must off skins, put the head back on the barrel, and re-fill it with the resulting wine. There are varying sizes of wooden tanks available in today's market as well that can be used for red varietal fermentation, including temperature-controlled options. Proponents of red varietal fermentation in oak contend some of the benefits are wines with increased color stability, fuller mid-palate structure, and better oak intregration. Many winemakers are opting for the addition of oak adjuncts (oak chips, oak dust, etc.) to tank fermentations, which will be discussed in a later post.

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