Winegrowers Supplies - De-acidification of Must
5. Biological de-acidification with Erbslöh Bitec Vino
Biological de-acidification of must is possible with a yeast of the type schizo-saccharomyces, e.g. Erbslöh Fermocid. During the fermentation of sugar a part of the malic acid in the must is also changed to alcohol.
A second technique is the use of lactic acid bacteria, which has been permitted since autumn 1990. Since autumn 1991 Erbslöh, in close collaberation with the company Condimenta who specialise in the breeding and drying of bacteria, have offered freeze-dried bacteria of the type Leuconostroc oenos under the name Bitec Vino. These bacteria cultures have been thoroughly tested. The bacteria were isolated out of wines which went through a spontaneous acid breakdown. Neutrality of taste, ability to break down acid in wines with a low pH value, growth reaction and tolerance of low temperatures were especially taken into account as selection criteria.
Bitec Vino is available as a freeze-dried acid breakdown and starter culture. With the bacteria you have an enormous amount of reactivating medium.
Bacteria for biological acid breakdown are considerably more sensitive than dry yeast. The reactivation of the bacteria must be carried out very carefully (for instrucions see below).
Conditions for the biological de-acidification in wine with Bitec Vino:-
SO2: Total SO2 not higher than 30 mg/l; Free SO2 not higher than 10 mg/l; ideally no SO2.
Residual Sugar: To give the optimal de-acidification: innoculate with bacteria towards the end of the alcoholic fermentation (residual sugar content should be under 4 g/l) or directly after. It is difficult to start the biological de-acidification in wines in which the yeast has already been deposited. Do not innoculate wines during turbulant fermentation.
pH-value: The pH-value of the wines should be 3.1 or higher (when necessary adjust it to pH 3.2 or higher with Chalk).
Temperature: The temperature in the wine should be 15 °C or over.
Storage: The freeze-dried starter culture can for a
short time (about 3-6 weeks) be stored in a fridge at about 4 °C.
Storage over a longer period (about 6 months) in the freezer at -18 °C.
During shipment the cultures cannot be maintained at -18 °C, and once thawed they should not be re-frozen, so the effective life is about 3 to 5 weeks.
Instructions for re-activation of Bitec Vino starter culture:
(for inoculating 500 - 1000 litres of wine after the alcoholic fermentation)
Rehydration of 'Vino':-
a) Stir the 'bacteria' contained in the sachet into 100 ml of boiled water (cooled to room temperature, 20 - 22 °C).
b) Leave the mixture standing at room temperature (20 - 22 °C) for 30 - 60 minutes.
Activation of 'Vino-R':-
a) Pasturise 4 litres of fresh grape juice (without SO2) or heat it and mix with 0.5 - 1 litre of boiled water and 3 litres of pasteurised or warmed wine (maximum 60 °C), without SO2 or less than 30 mg/l total SO2.
Set the pH value at pH 3.8 - 4.0 with Chalk; it should be about this with appropriate dilution.
Cool to room temperature, then stir in the reactivating preparation (Vino-R).
b) Mix well the bacteria solution (Vino) with the reactivation solution (Vino-R).
c) Keep the mixture covered for 48 to 96 hours at 22 to 25 °C. A well grown and active culture is recognised by the intensive development of CO2 (foam on the surface, vigorous bubbles). Under the microscope long chains of bacteria with 8 or more links can be seen.
d) Add the bacteria culture to the recommended amount of wine (residual sugar content under 4 g/l).