The Australian Wine Research Institute (AWRI) is undertaking a highly focused research project on cold stabilisation, as part of a push to significantly improve winery efficiency.
The project is important, because about half of all post-bottling wine instabilities identified by the AWRI helpdesk are caused by ineffective heat or cold stabilisation. A common error with cold stabilisation is that the wine is allowed to warm up before racking/filtering off the precipitated potassium bitartrate (KHT) crystals. This allows some KHT to re-dissolve into the wine and the wine is thus only stable to the temperature it was filtered at.
‘The AWRI analyses wines for cold stability as a service to the wine sector and provides support to winemakers through troubleshooting and education’, said Dr Keren Bindon, AWRI Research Manager.
‘Previously, AWRI Commercial Services has also run short-term commercial trials to better understand advances in cold stabilisation techniques, such as the use of crystallisation inhibitors like potassium polyaspartate (KPA) and carboxymethylcellulose (CMC).
One of the priorities of this new project is to better understand the tests currently used to determine a wine’s cold stability – and to assess whether these tests can be improved, or used more effectively. The project will also investigate when it is best to use certain tests; for example, when selecting the required dose of CMC or KPA.
‘Another question we want answered is “what makes a wine stable?”’, Dr Bindon said.
White wines typically suffer with cold stability issues more than red wines, and tend to have fewer large macromolecules (polysaccharides, tannins) than red wines.
‘It is thought that these large macromolecules can hinder crystallisation by preventing crystal growth. In our project we are trying to understand if, and how, these macromolecules affect cold stability.’
Dr Bindon said this research would hopefully lead to better understanding of the natural molecules in grapes or wines that could improve cold stability and how to optimise them in grapes and wine.
‘Yeast mannoproteins are already sold as a cold stabilisation product, but there may be others that are more effective.’
The project will also investigate alternative strategies to cold stabilisation.
‘Chilling wine for extended periods represents a high input cost in the winemaking process, so reducing this investment is a high priority.’
Dr Bindon said much headway had already been made using KPA and CMC as additives to prevent tartrate crystallisation in wine, but there was still room for improvement ‘since winemakers may not want to use additives, and there may be situations where they are less effective.’
‘Cold stability can be approached by preventing crystal growth, and for this – additives like CMC, KPA, or possibly naturally occurring wine macromolecules are effective’, Dr Bindon said.
‘Another approach though, is to reduce the potential for crystal nucleation, by reducing the saturation of potassium and bitartrate ions in wine.
‘Our project aims to look at how to optimise existing techniques for potassium (and/or bitartrate ion) removal, such as electrodialysis or ion exchange.’
Finally, the project will look at alternative approaches to potassium removal using natural or synthetic adsorbents, as well as to develop easily deployable and retrievable surfaces which are modified to induce crystallisation.
‘In this part of the study, a very optimistic objective is to be able to cold stabilise wine at higher temperatures, and therefore prevent the need for the energy investment in cooling wine.’
‘The work is still in its early stages, but already we are finding some exciting new results, which we want to trial further for their commercial relevance’, Dr Bindon said.