Notas de Aplicaciones
29sep/11

ENSAYO DE VINOS / WINE TESTS

CRYOTHERMOSTAT WITH STIRRER FOR WINE TESTS

Tartaric stability measurement of wines by Boulton test


J.P. SELECTA HAS DESIGNED A CRYOTHERMOSTAT WITH DRYING REFRIGERATED SYSTEM THAT DOESN’T NEED WATER DUE TO THE PELTIER EFFECT, AND INCORPORATING A STIRRER IN ORDER TO KEEP THE SAMPLE TO BE TESTED AT A STABLE TEMPERATURE.

BOULTON TEST
Tartaric stability measurement of wines: It is an analytical essay consisting of a quick precipitation of tartrate crystals, potassium acid, which are supersaturated in the wine.

The wine sample being analyzed is cooled to 0ºC and causes a quick precipitation of crystals by addition of approximately 10g/l of a potassium acid tartrate reagent powder.

The reduction of potassium is followed by a conductometric method.

When supersaturation is reduced to zero, there is no more precipitation and the conductivity value remains constant. Now the sample has the characteristics of a stable wine and this conductivity is the one which has to be taken into account. The conductivity measurement is very easy to do.

OPERATIONAL TECHNIQUE

  1. Pour 100ml of the wine sample in the beaker, measured with the probe.
  2. Set the stirring rod and place it in the bath over the stirrer.
  3. Insert the conductivity cell and the thermometer, if necessary, in the vessel and start stirring.
  4. If the conductimeter does not include temperature compensator, check the temperature in order it is stabilized at 0ºC.
  5. Then add a gram of potassium acid tartrate and read the conductivity every 2 minutes.
  6. Continue with the readings until you check that conductivity is the same for two or three consecutive times.

NOTES

A) The final conductivity value will be the one corresponding to this stabilized wine.This value will be compared with the cold treatment sample to determine the moment when stability is reached.
B) The difference between conductivity before adding bitartrate and final conductivity provides a potential stability measure with respects to bitartrate. In general, if this difference is lower than 5% of initial value, wine is stable; but if it is higher than 5%, wine is unstable.

Information provided by: Oenology department. Mrs. Valvanera Martínez de Toda Vallilengua – Technical Direction of BODEGAS COSTERS DEL SIO - LLEIDA.
Distributor: SOLTEVI, S.L - Vilafranca del Penedés.