Evaluation of the efficacy of a range of commercial bentonites on New Zealand Sauvignon Blanc wine Kirsten Creasy The following project was funded by New Zealand Winegrowers. 15-105 Introduction There are a number of different bentonite products on the market to remove heat unstable proteins, reducing the chance that a protein induced haze will form in a finished bottle of wine. A trial was set up to compare these products on a typical Marlborough Sauvignon Blanc. The primary objectives were to compare the quantity of bentonite required, measure the compaction of lees, analyse for differences in metals, pH, acidity or alcohol as well as assess if sodium dominant bentonites require smaller additions, but tend to have less compact lees, than calcium dominant products.
Method A newly fermented but protein unstable Sauvignon blanc was supplied by a Marlborough winery. There were 16 bentonite samples supplied to Hill Laboratories, with Table 1 showing the name of the bentonite, the supplier and the order that was used throughout the trial.
Protein Stability Trial A range of 1.1g/L to 1.9g/L in 0.2g/L increments was chosen as the initial rates. A control of 0g/L
Figure 1: The full collection of stock solutions. L-R: Aktivit, Nacalit, Microcol FT, Microcol CL-G, Microcol Alpha, Mastervin Compact, Plusgran Gel, Puranit, Optibent, Bentolit S, Pluxbenton N, Pluxcompact, Pharmabent, Spherobent J, Clarit BW 1100, Clarit WG.
was also included. To set up the trial, 100ml samples of wine were measured out, bentonite added, wines mixed, labeled and then left to settle at room temperature overnight. The next morning, a clear supernatant was poured off the 100ml sample into a separate beaker to filter the wine from. About 30mls of each treatment was filtered through a 0.45micron syringe filter and into a prepared tube ready for heating. Samples were heated for two hours at 80°C. For this initial trial, the wines were assessed by eye using a torch to shine through the tube, which would highlight any presence of a haze. A second trial was set up with a tighter range around the results from the first trial. After filtration, the turbidity was measured on the wines prior to heating using a Hach 2100N Turbidimeter. Once
the wines had been heated and cooled as described earlier, the turbidity was measured again.
was 1.6g/L. This matches the rate given by the winery who supplied the wine.
Lees Settling Trial
Lees settling
The second part of the experiment was to assess the lees settling capability of each of the bentonites. Once the protein stability point was established for each of the bentonites, one litre of wine was measured into 16 Imhoff cones as well as tall 1 litre plastic bottles to better mimic tank shape. After three days the total volume of lees from both the Imhoff cone and the plastic container were measured and expressed as a percentage of the total volume.
The results for lees compaction are more scattered than the stability results. In the Imhoff cones, the range is from 1.3% to 13% while the tall plastic containers ranged from 2.1% to 18.4%. The results show a clear grouping of calcium dominant bentonites with higher dose rates, but with generally very good compaction rates, which supports other trials and anecdotal evidence. If the results from the stability trial and the lees compaction are combined, the top five most effective bentonite products in this trial are (in order of efficacy): Nacalit, Aktivit, Optibent, Microcol CL-G and Clarit BW 1100. Pluxcompact is worth noting as it settled very well in the ‘tank’ containers at the
Results Protein Stability The bentonite addition rates ranged between 1.2g/L at the lowest end to 1.9g/L at the highest (Table 2 over page). The median
Scios
Laffort
Winequip
Esvin
Enartis
CAL
1. Aktivit 2. Nacalit
3. Microcol FT 4. Microcol CL-G 5. Microcol Alpha
6. Mastervin Compact 7. Plusgran Gel
8. Puranit 9. Optibent
10. Bentolit S 11. Pluxbenton 12. Pluxcompact 13. Pharmabent
14. Spherobent J 15. Clarit BW 1100 16. Clarit WG
Table 1: Bentonites and suppliers used in the trial
NZ WINEGROWER DECEMBER 2016/JANUARY 2017 // 75