Elevage

The term “Elevage” comes from French and in this case, relates to maturing or growing up. Wine is kept in oak barrels, steel tanks and carboys for 1-4 years to settle and mature. We mature our wine in new and used (“neutral”) oak barrels for 2-4 years. The new oak imparts desirable flavours and allows the intake of a small amount of oxygen (around 4g O2 per barrel per year) – this combination helps in the polymerisation of tannins and anthocyanins and improves the quality of the wine.

During elevage, the wine needs to be checked regularly for changes in key chemical properties and possible infections by spoilage organisms (creating “wine faults”). Barrels also need to be topped up regularly because wine evaporates through the wood staves. However, there is a trade-off: each time a container is opened, the wine gets exposed to oxygen and microbes in the air with the potential for spoilage. We open each barrel every 1-2 months, taste and measure the chemical properties and spectra and then decide whether we need to make adjustments (filtering, fining, cold stabilisation, other adjustments or racking/blending – each discussed in the following pages).  The following picture shows from left to right tasting, chemical testing and spectral analysis.

After adjustments have been made, if any, SO2 is replenished, and the barrel is topped up and closed. The right amount of SO2 controls spoilage organisms and excess oxygen – otherwise, their joint presence would tend to convert ethanol into acetaldehyde, creating a severe wine fault.

 

Measuring Chemical Properties

The extracted sample is tested and the results recorded in a spreadsheet which also calculates the required (if any) addition of SO2 in the form of KMBS (Potassium Metabisulfite). The tests are described in detail on the respective pages in the Laboratory section of the website.

  • Look, Nose & Taste: most important is to inspect the wine surface for film and smell and taste the wine to check for any irregularities or faults – this is done right after the barrel is opened.
  • Dissolved Oxygen (see the page on measuring Dissolved Oxygen)
  • Full set of OenoFoss measurements
  • UV-Vis Spectrum to measure Phenolics: (see the page on Measuring Phenolics in Wine)

Since 2017 we run all the tests, except DO, all the time on each vessel. The most important are Nose & Taste to check for faults and pH & SO2 to calculate necessary additions of Metabisulfite. If tasting or any of the tests reveal potential faults, we need to make corrections/adjustments.

 

Identifying & Correcting Wine Faults

The nose and tastebuds are man’s most valuable organs for identifying potential problems in wine. The following tables were excerpted and adapted from an ETS Laboratories’ Winemakers’ Quarterly (see www.ETSLabs.com), from the British Columbia Winemakers Association website www..bcawa.ca/winemaking/flaws.htm and Enotools website  www.enotools.com/wine-faults--whats-wrong-with-my-wine.html . They summarise key off-odours and tastes, the chemical compound responsible for them, their indicative sensory threshold, the most probable origin of the problem, how the problem can be prevented and possible corrections. Treatment should always be preceded by first eliminating the original cause. All treatment with chemical additions are problematic and should be done in stages or on samples first.

 

Replenishing Sulfur

The level of free SO2 which defines whether sulfur (in the form of KMBS - Potassium Metabisulfite) needs to be added. See “Adding SO2” on the page “Steps 3-11: Upfront Wine Making Decisions” in the Winery Section. We add KMBS when topping up after adjustments have been made, as KMBS needs to be first dissolved in a small amount of wine.

 

Topping up

Topping Up Tanks.jpg

Oak barrels need to be topped up regularly because a small amount of wine (called “angels’ share”) evaporates through the staves. The evaporation rate is usually around 3% p.a., depending on the humidity in the cellar. Wine components inside the barrel migrate through the wood at various rates and evaporate from the outside surface. Assuming the migration rates of the liquid components (say 87% water and 13% alcohol) depend mostly on the differences in concentrations between the inside and outside of the barrel, the alcohol concentration in the wine changes. We keep the cellar at around 60% humidity, so the concentration differences are 27% for water and 13% for alcohol (assuming the alcohol in the cellar air is zero). Therefore at 60% cellar humidity water leaves the barrel twice as fast as alcohol, and the 3% annual evaporation consists of approximately 93% water and 7% alcohol. If you start the year with 100L wine at 13% alcohol, then you end the year with 87-3%*93 = 84.2L of water and 13-3%*7 = 12.89L of alcohol and the new alcohol concentration in the remaining  97.09L of wine is 12.89 / 97.09 = 13.27%, an increase of 0.27%. This calculation illustrates why barrel cellars should be kept humid.

For topping up, we use a system based on kegs sold by St. Patricks of Texas (http://www.stpats.com/index.htm). The wine is stored in a stainless steel keg and preserved under minimally pressurised Argon. The system has a dispenser/topping gun which allows to easily top up barrels and carboys with minimal exposure to air while keeping the wine reserve sealed. We extended the setup sold by St. Patrick’s to two kegs to allow dispensing different top-up wines, and we adjusted the inert gas injection. Whenever we refill the kegs or open them up for inspection, we need to close the keg and replace the air with Argon. This is done in 3 cycles: first extracting the air with a vacuum pump and then filling the vacuum with Argon; then twice extracting the Argon/air mix and refilling with Argon. After 3 cycles the gas above the wine should be close to 100% Argon.

 

 

Data Management

We record all elevage actions in the Cellar Actions table. Here is a screenshot of the data entered on January 18, 2018, for the barrel containing the 2017 Merlot-PetitVerdot-CabFranc mix.

DataM Topping Up.png

Usually, we enter this data in the “INPUT: Cellar Action by Cellar Batch Collection”-layout shown on the previous page.

 

Last year: 2017 elevage

We have not yet developed a layout which succinctly summarises the elevage actions across all barrels during a year. However, we have started to develop a layout which summarises all elevage actions for a particular barrel across all years, the “Review: Cellar Batch”-layout. Here is a screenshot of the first tab in that layout for the 14-13CSCHwb2 barrel.

 

 

 

 

DataM 2017 Elevage.png

 

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Last updated: February 29, 2018