Research has previously shown that carrageenan, a naturally occurring polysaccharide extracted from red seaweeds, can protein stabilise white wines effectively. As carrageenan is a renewable substance, it poses a very attractive alternative to bentonite. There are many types of carrageenans commercially available and the aim of this study was to evaluate these different types for their efficacy in protein stabilising white wines during the different stages of the white wine making process. Their impact on wine chemical and sensory analyses were also evaluated.
- Various commercial carrageenans were characterised for water- and wine-solubility using viscosity index measurements.
- They were then screened, using different dosages, for their heat stabilising properties in a Riverland (Australia) Chardonnay finished wine that served as an initial screening process.
- A change in turbidity before and after heat treatment of less than 2 NTU was considered a recommended dose. Heat treatment comprised of 80°C for two hours and then 20°C for three hours.
- Carrageenans that stabilised the wine at a dosage of less than 140 g/hl were considered for larger scale trials.
- For the preliminary clarification trials three treatments were conducted. In T1 Sauvignon blanc juice (Adelaide Hills) was settled without pectinase enzymes for 24h, carrageenan was added and allowed to settle for 24h and the chitosan (a flotation agent) was added and allowed to settled for 24h.
- In T2 and T3 the juice was clarified with 3ml/hl pectinase enzyme before carrageenan were added.
- In T2 another enzyme mix containing beta-glucanse and cellulose was added 24h after carrageenan addition.
- The purpose of the chitosan and additional enzyme additions were to see if the filterability of final wines will be improved.
- All treatments and controls were fermented with Maurivin PDM at 15°C.
- Adelaide Hills S. blanc from two vintages was also used for the larger scale trials.
- In these trials three different types of carrageenans were added at the juice stage during cold settling, after the onset of fermentation or in the finished wine.
- Bentonite was added to wine as a positive control.
- Various pre- and post-bottling analyses were done on the wines.
- During the screening process it was found that kappa-carrageenans were the most effective in protein stabilising wines.
- The use of pectinase enzymes to clarify white juice before carrageenans were added, was the most effective treatment to improve filterability of wine, of the three compared treatments in the clarification trial.
- Compared with the untreated and bentonite controls, the addition of carrageenans to juice and during fermentation increased the fermentation time with two days and one day respectively.
- Natural kappa-carrageenans contain potassium (K) ions, but with ion-exchange sodium (Na) containing carrageenans can be produced. The latter is more cold-stable. It was found that the Na-carrageenan produced half the lees volume created by bentonite, which is a promising attribute. However it does also raise the Na content of wines in some cases to unacceptable levels.
- Potassium containing carrageenan did not raise the K levels of wines. It did however raise the calcium (Ca) levels of wines as carrageenan also contain low levels of Ca.
- Unlike bentonite carrageenans float when added to finished wines. When added to juice or during fermentation it settles, since there are other solids to help it settle.
- In some cases the carrageenans added to the juice did not completely stabilise the wines.
- The iota-carrageenan tested decreased the filterability of the wine and is therefore not a viable alternative to bentonite.
- In terms of sensory the best time to add carrageenan is to finished wines.
- Bentonite addition to wine showed a reduction in aroma and flavour compared to untreated control and carrageenan treated wines.
SIGNIFICANCE OF THE STUDY
The study indicates that K-containing kappa-carrageenan is a viable alternative to protein stabilise white wines. Carrageenan is already a permitted wine additive in Australia and New Zealand.
Ratnayake, S., Stockdale, V., Grafton, S., Munro, P., Robinson, A., Pearson, W., McRae, J. and Bacic, A. (2019). Carrageenans as heat stabilisers of white wine. Australian Journal of Grape and Wine Research, 25: 439-450. doi:10.1111/ajgw.12411
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