 |
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
&
amp; 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