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Procedure to Determine the Titratable Acidity of Grape Juice, Must or Wine
Using a Colour Indicator
(see advantages and disadvantage of various methods)
1. - Secure an adequate, representative sample of grape juice, must or wine.
2. - Prepare sample -
3.- Set up a 25 ml or 50 ml burette on a retort stand, as per diagram, and fill with your standardized 0.1 M sodium hydroxide (NaOH) solution.
- Allow to settle to obtain a clear sample.
- Degas the sample.
4.- Zero or note the level of the 0.1 M NaOH solution in the burette and record.
5. - Neutralise 100 ml of distilled/deionised water (H2O).
6. - Pipette accurately, 10 ml of prepared sample into the 250 ml container, holding the dist. H2O.
Note:that when the 10 ml (acidic) sample was added to the neutralized, pink coloured distilled H2O, the pink solution turned clear due to the introduced acidity.
7. - Titrate the sample solution until a pink colour end point is achieved that persists.
8. - Record the new burette level and calculate the titratable acidity.
Using a 10 ml sample and exactly 0.100 M NaOH solution -
|Titratable Acidity (g/L) || = || titre (ml) || * || 0.75 || . || . ||(10 ml sample, 0.100 M NaOH)|