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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 -


• Allow to settle to obtain a clear sample.
  
  
• Degas the 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.

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)