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Save money and wine by choosing the right bentonite

Save money and wine by choosing the right bentonite

Bentonite has long been used as a fining agent for wine to remove protein and prevent the formation of unattractive sediments. Studies into the hidden costs of bentonite fining have estimated the loss in revenue to the world's wine industry to be around one billion dollars, with a volume equivalent to the total white wine production of New Zealand (Majewski et al. 2011).
Bentonite can also be detrimental to wine quality if used in excessive levels and has been proven to significantly remove volatile compounds (Sanborn et al. 2011) such as Ethyl dodecanoate that contributes to black cherry and chocolate aromas (Tomasino et al. 2012). Some studies have indicated the benefits of adding bentonite in two stages to try and reduce the amount used, thereby minimising the amount of aroma removed (Marangon et al. 2012). This requires a prediction of the amount of bentonite required to achieve stability which is not always feasible due to both varietal and vintage variation. These studies illustrate the significant cost bentonite has and the importance of not treating bentonite simply as another commodity purchased for vintage.
Different ions or combinations of ions can exist in bentonite and traditionally sodium bentonites have been favoured for their low cost and efficient protein removal. However, this has been at the trade-off of excessive lees production, extended settling times and longer swell times. Bentonite clays are hydrated aluminium silicates that posess lattice-like structure containing layers of negatively charged sheets. The chemical composition of these layers govern not only the swelling process, but more importantly the cost effectivness of the bentonite depending on the dominant cation present within these layers. Technologial advances have allowed a new generation of activated bentonite called Pluxcompact to be produced, allowing the winemaker to recover more wine or juice while still creating protein-stable wines.
Enartis Pacific and E.E. Muir & Sons have collaborated to form an independent study conducted by a NATA accredited laboratory (The Wine Clinic - Barossa Valley, SA). Two areas were investigated by The Wine Clinic for this trial to investigate the real cost differential between currently available bentonites.
Firstly, three 2012 white wines (Chardonnay, Sauvignon Blanc and Riesling) were chosen for bench trials to determine the dosage rate required to achieve stability between sodium bentonite (Na bent), Pluxcompact activated bentonite, and two different sodium calcium bentonites currently in the marketplace (Na/Ca Bent #1 and Na/Ca Bent #2). Stability was defined by a difference of less than 1 NTU between the control and the bentonite-treated wine. See Figures 1, 2 & 3 for results.
Secondly, an investigation into the volume of lees generated between these four bentonites was performed on the Chardonnay wine with a standard dosage rate of 2g/L. Lees levels were measured in volumetric cylinders and calculations were then performed to estimate the amount of lees of each bentonite at the dosage rate required to reach stability (determined in part one of this trial).
Calculations of the combined cost of bentonite and the cost of wine lees was then performed for a range of different fruit costs. The aim was to quantify the real costs of bentonite fining and the potential cost savings of switching from sodium bentonite to an activated bentonite with grapes purchased at $250, $500 and $1000/tonne and an assumed yield of 750L/tonne.
Results indicate that the least amount of sodium bentonite is needed to achieve heat stability in the Chardonnay and Riesling wines. The Sauvignon Blanc wine was very close to being stable at 0.8g/L with both the sodium bentonite and Pluxcompact. The sodium bentonite's performance was expected, since it was the only sodium bentonite trialled and these are more efficient at removing protein due to the prevalence of the sodium cation (Bowyer and Moine-Ledoux 2007). Notably, the next bentonite with the lowest dosage rate was Pluxcompact in all three wines tested.
To determine the levels of lees created between the four different bentonites, a dosage rate of 2g/L was applied to the 2012 Barossa Valley Chardonnay. Volume of lees created was able to be calculated using the graduated measuring cylinders. Refer to Figure 4 for a photo and table of results.
Results indicate a significant variability between the amounts of lees formed but lower levels of variation between turbidity in the clear wine above the lees. From the photo it is obvious that Pluxcompact and Na/Ca bentonite #1 exhibit much better compaction properties and produce significantly lower amounts of lees than both the Na bentonite and the Na/Ca bentonite #2. If we now combine the results from these two trials, we can extrapolate the real cost differential between using a straight sodium bentonite compared to the Pluxcompact-activated bentonite by including not only the dosage rate required to achieve stability, but also the volume of wine that is lost via lees.
Looking at the 2012 Barossa Valley Chardonnay lees results, we can extrapolate the lees levels at the specific dosage rates required to achieve stability based on the assumption that there is a linear relationship between dosage rate and levels of lees. The grey cells highlighted in Figure 5 indicate a heat-stable result for both bentonites and the estimated percentage of lees at these dosage rates.
Assume the following plausible parameters, 750L/tonne extraction and cost price of $1/kg for the Sodium bentonite and $2/kg for Pluxcompact. When we look at the several examples based on these assumptions and using grapes costed at $250/tonne (Figure 6), $500/tonne (Figure 7) and $1000/tonne (Figure 8) we can see the significant cost savings in using activated bentonites in both commercial and premium wine parcels even when it is double the cost of a sodium bentonite.
This proves that the cheapest bentonite option will not always give winemakers cost savings that the initial purchase price and addition rates might suggest. Add to this the ease of use for Pluxcompact bentonite, with maximum pre-swell time of three-six hours in cold water (no hot water required) and even greater savings can be achieved.
This clearly demonstrates that activated bentonites like Pluxcompact can improve the winemaking process by providing an increased wine volume at a reduced overall cost.

References
Bowyer, P. And Moine-Ledoux, V. (2007), 'Bentonite - it's more than just dirt' Aust N.Z. Grapegrower Winemaker; Feb 62-68.
Majewski, P., Barbalet, A. And Waters, E. (2011),'$1 billion hidden cost of bentonite fining' Aust N.Z. Grapegrower Winemaker; June 58-62.
Marangon, M., Pocock, K. F., and Waters, E. (2012), 'The addition of bentonite at different stages of white winemaking and its effect on protein stability' Aust N.Z. Grapegrower Winemaker; May 71-73.
Sanborn, M., Edwards, C. And Ross, C. (2011), 'Impact of fining on chemical and sensory properties of Washington State Chardonnay and Gewürztraminer wines' Am .J. Enol Vitic, March vol 61 no 1 31-41.
Tomasino, E., Harrison, R., Breitmeyer, J. And Frost, A. (2012), Four chemicals that influence the aroma of New Zealand Pinot Noir wine-Ethyl Octanoate, Ethyl Decanoate, Phenethyl Alcohol and Benzaldehyde' 2012, 8th International Cool Climate Symposium, Feb 1-4, Hobart, Tasmania.

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