Laboratory Test Procedures arrow Protein Stability arrow Protein Stability using Bentonite test

Protein Stability using Bentonite test

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Rapid determination of the amount of Bentonite needed for wine and juices

To find out whether Bentonite fining is necessary for the wine or juice under investigation, the following preliminary test is carried out:

  • 1 part of BENTONITE TEST reagent is added to 10 parts of filtered wine (room temperature!). The addition of 1 part of reagent to 10 parts of wine need only be approximate. In practice, it is easiest to start from the total amount of wine in the flask (about 50cm3) and to add about 5cm3 of the BENTONITE TEST reagent by means of the measuring beaker provided. In wines in need of Bentonite treatment, the wine turns turbid. With a little practice, the amount of Bentonite needed can be concluded from the degree of turbidity.
  • Any green coloration which may appear at the same time is of no significance. It even makes only slight turbidity easier to recognize. If a green-blue coloration quickly starts and this is a disturbance, it is possible to use a colorless BENTONITE TEST reagent instead of the yellow reagent. The greenish-blue coloration starts somewhat later, a fact which should be borne in mind when evaluating the turbidity. We recommend the colorless reagent for light red wines and strongly de-acidified white wines. For dark red wines we recommend “BENTONITE TEST for red wine”, also a colorless reagent.

The rule of thumb is as follows:

  • Slight turbidity: 50 to 100g of Bentonite per 100 Litres of wine
  • Medium turbidity: 100 to 250g of Bentonite per 100 Litres of wine
  • Extreme turbidity: 250 to 400g of Bentonite per 100 Litres of wine

To determine the exact amount of Bentonite, fining experiments have to be carried out as follows.

Preliminary fining experiment:

1) Fill the wine into the flask up to the O mark.

2) Adjust exactly to the O mark by means of the pipette provided.

3) Vigorously shake the bottle with the Bentonite suspension (yellow label).

4) Add the well-mixed Bentonite suspension to the wine in the flask in the amount estimated in the preliminary test.

5) Close the flask by placing a thumb over it, and shake for 2-3 minutes.

6) Then filter through BENTONITE TEST special folded filters in an Erlenmeyer flask.

7) Add 1 part of BENTONITE TEST reagent to 10 parts of filtered wine (follow the instructions in the preliminary test).

    The wine is protein-free when no turbidity appears.

The amount of Bentonite needed is obtained most accurately by running 3 fining experiments for each wine or fruit juice with rising amounts of Bentonite, and observing the amount which just makes the drink protein-free.

It should be stressed that the Bentonite suspension used should always be from the Bentonite employed in practical fining in the cellars.


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