5
Titratable acidity measures the total titratable acidity and differs from pH as it also includes the
buffering capacity of the milk constituents. Titratable acidity in dairy products, is determined by
titrating a sample with sodium hydroxide to a fixed endpoint pH (pH 7.00 or a phenolphtalein
endpoint of pH 8.30). The actual neutralization of milk occurs at an endpoint of pH 7.00, however,
standard methods utilize the phenolphtalein endpoint value. The results will differ depending upon
which endpoint is utilized. The endpoint can be determined visually using color change produced by
phenolphtalein indicator or less subjectively, using a pH electrode as the indicator in a potentiometric
acid-base titration.
Titratable acidity can be expressed in various units values:
Soxhlet Henkel degrees (°SH)
- mostly used in Central Europe
This value is obtained by titrating 100 mL of milk with 0.25N NaOH, using phenolphtalein as
indicator.
Thorner degrees (°Th)
- mostly used in Sweden and the CIS
This value is obtained by titrating 100 mL of milk, diluted with 2 parts of distilled water, with 0.1N
NaOH, using phenolphtalein as indicator.
Dornic degrees (°D)))))
- mostly used in Netherlands and France
This value is obtained by titrating 100 mL of milk, diluted with 2 parts of distilled water, with N/9
NaOH, using phenolphtalein as indicator.
Percent lactic acid (%l.a.)))))
- frequently used in the UK, USA, Canada, Australia and New Zeeland
This value is obtained in the same way as °D, dividing the result by 100.
The result can be easily converted into any of the other units as shown in the table below:
H
S
°
h
T
°
D
°
.a
.l
%
5
2.
0
1.
0
1
1
1.
0
1
1
1
0.
0
1
5.
2
5
2.
2
5
2
2
0.
0
4.
0
1
9.
0
9
0
0.
0
9
/
4
9
/
0
1
1
1
0.
0
