What is stabulation?
During “normal” winemaking practices, the juice lees (solids) are removed from the juice after pressing by sedimentation or flotation and subsequent racking. This process is usually completed within 48 hours.
Stabulation is the process of keeping the pressed juice in contact with the fine juice lees by regularly stirring up the solids. Settling or flotation and racking operations are therefore delayed until stabulation is finished.
What is the goal of stabulation?
The goal of stabulation is to extract aroma precursors and other beneficial compounds from the solid lees particles that would eventually contribute to an enhanced wine aroma profile, as well as the extraction of compounds that could improve the mouthfeel of the resulting wine.
At what temperature is stabulation done?
Stabulation is usually done at cooler temperatures (usually between -2°C and +3°C) to avoid yeast activity and alcoholic fermentation. It is important to prevent fermentation, because once it starts, clarification of the juice will become challenging, resulting in full solids fermentation, with an attendant risk of reductive characters developing.
After the juice has been stabulated, it is allowed to settle before racking, warming, and inoculation. Increasing the temperature to at least 8 – 10°C is advised to avoid the risk of excessive oxygenation, as oxygen dissolution will occur much faster at the low stabulation temperatures, with subsequent risk of oxidation. During stirring and racking operations, dry ice or inert gasses are recommended to prevent oxygen exposure.
The temperature of the clear juice before inoculation should also be considered and managed to prevent the unsuccessful onset of alcoholic fermentation due to too-low temperatures. The time it takes to “heat up” the juice should be minimised to prevent unwanted microbial activity before alcoholic fermentation occurs.
How often is the lees stirred?
The fine lees is usually stirred every 12 hours, but the frequency can be increased or decreased depending on the desired outcome.
For how long should I perform stabulation?
The duration of stabulation can vary and usually ranges between four days and two weeks, depending on the health of the harvested grapes and the desired outcome.
Specific regimes of varying stabulation durations can also be followed according to the employed temperature. The lower the temperature, the longer the duration of stabulation can be applied. At low temperatures (between 0 – 2°C), a stabulation time of four days to three weeks can be applied. As the temperature increases, it is advised that the stabulation duration be reduced. As a guide, at 8°C, a stabulation time of 48 hours is recommended, while this duration is decreased to 24 hours at a juice temperature of between 10 and 12°C. The duration of stabulation will also depend on the quality of the fruit. Healthy grapes with minimal rot will have fewer unwanted microbes and, therefore, a lower risk of unwanted microbial activity during the stabulation process.
How can stabulation improve my wine?
A study performed using healthy Austrian Sauvignon blanc grapes showed that seven days of stabulation resulted in a statistically significant increase in the fruity volatile thiol 3-mercaptohexanol (3MH) (to around 700 ng/L) when compared to the control, which did not undergo stabulation (± 500 ng/L). Three days of stabulation did not increase the 3MH concentration when compared to the control. Stabulation (three or seven days) did not result in differences in 3-mercaptohexyl acetate (3MHA) concentrations compared to the control treatment.
Differences in isobutyl-2-methoxypyrazine (IBMP) concentrations were reported. Three days of stabulation resulted in a slightly lower IBMP concentration (± 15 ng/L) in the stabulated treatment compared to the control (± 19 ng/L). Seven days of stabulation resulted in a wine with an average concentration of 25 ng/L IBMP and an increase in the compounds responsible for green-type aroma descriptors. However, these results were not statistically significant under the conditions of the specific study.
What are the other benefits of stabulation?
Stabulation also allows for sequential fruit presses off a large vineyard as juice can be added to the stabulation tank over several days provided the process is monitored and well controlled.
In addition to the enhanced aromatics and improved mouthfeel reported, increased colour stabilisation of rosé wines and decreased unwanted fatty acids have also been reported.
Conclusion
Stabulation is the anaerobic mixing of juice lees for several days before clarification. If monitored and controlled successfully, the process could contribute to the quality and sensory experience of the resulting wine.
References
- Goode, J. Juice stabulation, an interesting winemaking technique.
- Philipp, C., Eder, P., Patzl-Fischerleitner, E. & Eder, R., 2022. Stabulation (lees stirring) in must as a method for aroma intensification: A comparison with skin contact and a classical version of Traminer and Sauvignon Blanc in Austria. IVES Conference Series, Wine Active Compounds.
- Seabrook, A., Van der Westhuizen, T., 2018. Stabulation – Seriously Rosé or Sauvignon Blanc? Grapegrower and Winemaker 649, 59.
This article was first published on the Sauvignon Blanc South Africa website (www.sauvignonblanc.com) in January 2024. It is reproduced with permission from Sauvignon Blanc South Africa and the author.
For more information, contact Carien Coetzee at carien@basicwine.co.za.
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