Managing wine instability

Wine stability is a large and very important area in winemaking. There are many aspects of wine that require stabilising throughout its life, including pectin stability, oxidative stability, colour stability, protein stability, tartrate stability and microbiological stability to name some.

This section looks at both heat (protein) stability and cold (tartrate) stability and areas where innovation and advances in research have provided different options for winemakers to explore. Also read top tips for wine stabilisation from Wine Australia.

Heat stabilisation

Most wineries remove unstable proteins from white wine before bottling by fining with bentonite. Often winemakers use the same dose each year, yet the amount of protein present in grapes is affected by ripeness and disease and so will differ from year to year. A bentonite trial should be carried out each year to calculate the minimum amount required to reduce protein levels and infer protein stability.

Here are a number of useful resources concerning the application of bentonite for heat stability.

Practical tips on lab trials and preparation.

Testing for heat stability.

Further reading

Bentonite

Marangon, M. Pocock, K. F. Waters, E.J. The addition of bentonite at different stages of white winemaking and its effect on protein stability. Australian & New Zealand Grapegrower & Winemaker (580) : 71-73; 2012.

Protein stability tests and their effectiveness in predicting protein stability during storage and transport. Australian and New Zealand Wine Industry Journal, Volume 23, Issue (2), 40-44 Pages, 2008 Pocock, K.F.; Waters, E.J.; Herderich, M.J.; Pretorius, I.S.

Alternatives

Marangon, M. Lucchetta, M. Duan, D. Stockdale, V.J. Hart, A. Rogers, P.J. Waters, E.J. Protein removal from a Chardonnay juice by addition of carrageenan and pectin. Australian Journal of Grape and Wine Research. 18 (2) : 194-202; 2012.

Marangon, M. Lucchetta, M. Waters, E.J. Protein stabilisation of white wines using zirconium dioxide enclosed in a metallic cage. Australian Journal of Grape & Wine Research 17 (1) : 28-35; 2011.

Marangon, M. Sluyter, S.C.V. Robinson, E.M.C. Muhlack, R. Holt, H. Haynes, P.A. Godden, P.W. Smith, P.A. Waters, E.J. Degradation of white wine haze proteins by Aspergillopepsin I and II during juice flash pasteurization. Food Chemistry 135 (3) : 1157-1165; 2012.

Marangon M,  Proctase and other alternatives.   AWITC 2015

Robinson, E. Scrimgeour, N. Marangon, M. Muhlack, R. Smith, P. Godden, P. Johnson, D. Beyond bentonite. Wine & Viticulture Journal 27 (6) : 24–30; 2012.

Robinson, E. Scrimgeour, N. Marangon, M. Muhlack, R. Smith, P. Godden, P. Johnson, D. Beyond bentonite. Wine & Viticulture Journal 27 (6) : 24–30; 2012.

Robinson, E. Scrimgeour, N. Marangon, M. Muhlack, R. Smith, P. Godden, P. Proctase as a bentonite alternative – what’s the latest? Technical Review (201) : 6-10; 2012.

Waters, E. , Alexander, G. , Muhlack, R. , Pocock, K. , Colby, C. , O’neill, B. , Høj, P. And Jones, P. (2005), Preventing protein haze in bottled white wine. Australian Journal of Grape and Wine Research, 11: 215-225. doi:10.1111/j.1755-0238.2005.tb00289.x

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Cold stabilisation

Grape juice is typically supersaturated with soluble potassium bitartrate (KHT), as fermentation begins and ethanol content accumulates, the solubility decreases and with it a slow precipitation of KHT. If left, bottled white wines may develop a crystalline deposit that could be misinterpreted by some consumers as an issue with the wine.

In a conventional method of cold stabilizing, a wine is chilled to a temperature just above its freezing point and is held at that temperature for two to three weeks. Chilling the wine lowers the solubility of KHT and facilitates its crystallization and precipitation.  This process can be expedited by the addition of finely powdered crystals of KHT which act as a source of nucleation.

Further reading

Measurement of cold stability of wine.

Cold Stability, CMCs and other crystallization inhibitors.

Alternatives

Carboxymethylcellulose (CMC)

CMC is a crystallisation inhibitor used to infer cold stability on wines and was approved for winemaking in Australia in 2011. CMC has the ability to crosslink with proteins in wine to form a haze. Consequently, wines must be protein stable before any CMC additions. In fact, a wine must be ‘bottle ready’ before making a CMC addition and no subsequent physicochemical modifications can be made after the addition. That is, all blending, acid adjustments or deacidification treatment, concentrate additions etc. must be made and the wine must be free of any particulate matter before CMC treatment. Note that lysozyme is a protein and can generate a haze if present with CMC.

Further reading

Coulter, A.D. KHT deposits and cold stability. Australian & New Zealand Grapegrower & Winemaker (629), 76; 2016.

Coulter, A.D. Holdstock, M.G. Cowey, G.D. Simos, C.A. Smith, P.A. Wilkes, E.N. Potassium bitartrate crystallisation in wine and its inhibition. Australian Journal of Grape and Wine Research 21 (S1) : 627-641; 2015.

H. Claus, S. Tenzer, M. Sobe, M. Schlander, H. König, J. Fröhlich, Effect of carboxymethyl cellulose on tartrate salt, protein and colour stability of red wine,  Australian Journal of Grape and Wine ResearchVolume 20, Issue 2. First published: 12 March 2014

Marsh, R. Mills, S. Assessment of CMC-induced tartrate stability over an extended period. Wine & Viticulture Journal 27 (6) : 48–51; 2012.

Treadwell, K. CMC – The bean counter’s friend. Australian & New Zealand Grapegrower & Winemaker (576) : 59; 2012.

Wilkes, E. You’ve got to be a hot shot to hit the moving target of cold stability. Australian and New Zealand Grapegrower and Winemaker, No. 600, Jan 2014: 43-46.