The use of chitosan as an alternative to bentonite fining




The aims of the study were to investigate if chitosan can modify wine haze potential in a similar manner as bentonite, as well as if such fining will have an effect on wine chemistry.
 
The haze-forming proteins in wine comprise of chitinsases, thaumatin-like (TL) proteins and beta-glucananses. Various factors in wine can influence haze forming including pH, ionic strength, alcohol concentration, polysaccharide and polyphenol concentrations, as well as the presence of sulphates. Usually bentonite is used as fining agent to remove potential haze-forming proteins, but bentonite can also remove certain aroma compounds, having a negative effect on wine quality. Chitin is able to remove chitinases, however, it is not permitted for use in winemaking. Chitosan, a derivative of chitin, is allowed. Currently it has been approved for use in winemaking by the OIV with the main purpose of controlling Brettanomyces spoilage.

Experimental layout
  • Wine samples were obtained from 20 l small scale fermentations of Moscato juice inoculated with EC 1118.
  • No sulphur was added and MLF prevented.
  • Model wine solutions with different combinations of organic acids were prepared.
  • 1g/l Chitosan was added to the model wine and real wine samples. Un-fined controls were kept.

Results
  • Chitosan reduced both tartaric acid and malic acid in the model wines. The highest reduction for tartaric acid was 0.65 g/l and for malic acid: 0.46 g/l.
  • Total protein content of wines fined with chitosan was on average 14% lower than the control.
  • Chitosan fined wines were almost completely deprived on chitinases.
  • There was no significant effect on the TL-proteins.
  • After a 60°C heat test the control NTU was 11.07 and the chitosan treated wine: 1.95.
  • After a 62°C heat test the control NTU was 8.96 and the chitosan treated wine: 2.10.
  • Chitosan did not removed any polyphenols.
  • Chitosan reduced the Calcium, Potassium, Iron and Sodium content of wines.
  • Chitosan reduced some of the free terpenols such as nerol, geraniol and linalool. The glycosylated precursors were mostly unaffected.
  • ß-damascenone was unaffected.
  • No other classes of aromatic compounds were affected by chitosan treatment.

Significance of the study
Due to the reduction in protein haze, chitosan seems to be a viable alternative to bentonite treatment. Due to the removal of Potassium and Calcium ions, it can also have a positive effect on the tartrate stability of wines. The removal of iron reduces the wine’s oxidative capacity.
No sensory analysis was done in this study and chitosan’s effect on free terpenols should be further investigated.
Only fungal derived chitosan (Aspergillus niger) is approved for use in winemaking.

Reference
Donato Colangelo, Fabrizio Torchio Dante Marco De Faveri and Milena Lambri. The use of chitosan as alternative to bentonite for wine fining: Effects on heat-stability, proteins, organic acids, colour, and volatile compounds in an aromatic white wine. Food Chemistry, Vol. 264, 30 October 2018, Pages 301-309. https://doi.org/10.1016/j.foodchem.2018.05.005
This article is not open access.

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