2. Principle
When formaldehyde added to a milk sample, Amino
group of amino acid of milk protein binds with
formaldehyde and leaving the carboxyl group free.
This can set free H+ ions which can be estimated
by titration with standard alkali.
4. Reagents and material required
Burette
Pipette
Beaker
Formalin (40%) neutral, obtaining by adding a small amount of NaOH, using 2 drops of
phenolphthalein as an indicator.
Potassium oxalate solution (neutralized to phenolphthalein)
NaOH solution 0.1M
Phenolphthalein indicator (0.5% in ethyl alcohol)
5. Procedure
10 ml milk sample pipette out in a dry conical flask.
Add 2 drops of phenolphthalein
Add 0.4 ml potassium oxalate (it binds calcium ions) to
encounter the disturbing effects of calcium of milk.
Set aside for 2 minutes
Titrated with 0.1M NaOH till end point achieved, note down
burette reading (V1).
2 ml neutral formalin added, mixed well, diluted with 10
ml CO2 free water.
1 ml phenolphthalein added.
Titrated with 0.1M NaOH till end point achieved, note down
burette reading (V2).
