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GEA Niro Method No. A 19 a |
Revised: September 2006 |
1. Principle
The titratable acidity is expressed as % lactic acid and is determined by titration of a known amount of reconstituted milk with 0.1 N NaOH using phenolphthalein as indicator.
2. Scope
This method may be applied for all kind of dried milk products.
3. Apparatus
1. Analytical balance ± 0.1 mg
2. Methrom autoburette
3. Solubility index mixer, Snijders, The Netherlands.
Speed 3800-4000 rpm
4. 100 ml Erlenmeyer flask
5. 20 ml pipette, other sizes may be used
4. Chemicals
1. Titrisol, 0.1 N NaOH - R 35, and S 26, 27, 37/39
R » DK risk sentences
S » DK safety sentences
2. Phenolphthalein
3. 96% Ethanol
5. Reagents
1. 0.1 N NaOH.
Dilute the Titrisol solution to 1 litre. Standard Method no. R-7.1
2. 1 % Phenolphthalein solution
Dissolve 1g of phenolphthalein in 50 ml 96% ethanol and dilute to
100 ml with deionized water.
6. Procedure
1. Disperse and dissolve the following amount of powder in 100 ml of deionized water using the mixer.
Powder:
Skim or buttermilk: 10 g
Whole milk: 13 g
Whey: 6 g
2. Allow the mixture to stand for approx. 1 hour, stir gently.
3. Pipette 20 ml into a 100 ml Erlenmeyer flask.
4. Add 0.5 ml of phenolphthalein and titrate with 0.1 N NaOH until a faint pink colour persists for 30 sec.
7. Result
& nbsp; 
8. Remarks
1. Ref. 1 (ADMI) prescribes that exactly 17.6 ml of milk solution is used.
If that is the case the Titratable Acidity can be calculated by dividing ml 0.1 N NaOH by 20.
2. Adjust the amount of milk used in the titration until a reasonable amount of base is used.
9. Reference
· ADMI, Standards for grades of dry milk, bulletin 916, revised 1990
· GEA Niro Research Laboratory