Hanna Instruments HI 84529-01 - Manual (Page 7)

www. hannainst .com 7 Description
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, with N/9 (0.11 N) NaOH, using phenolphtalein
as indicator.
Percent lactic acid (%l.a.) - frequently used in the UK, USA, Canada, Australia
and New Zealand. This value is obtained in the same way as °D, dividing the
result by 100.
The titratable acidity values will vary depending on the method used. Select
Low 50 to titrate a non-diluted sample, or select Low 20 / High 20 to titrate
20 mL or 20 g samples that are diluted with twice its volume of deionized a
distilled water. The HI 84529 uses methods based on AOAC International
and Standard Methods for the Examination of Dairy Products. Both of these
method report titratable acidity as % lactic acid, a rough conversion factor
can be used to convert the results to the other available units:
The HI 84529 can be customized to meet the needs of any dairy analysis
lab. Samples can be titrated by weight or volume, diluted or non-diluted (low
range only) and titrated to a fi xed pH end point that can be adjusted by the
user.
The methodology for titratable acidity in dairy products is based on
neutralization reaction where the acids in the sample (i.e. lactic acid) reacts
with a base (i.e. sodium hydroxide) to produce water:
H + +OH¯—>H
2
O
From: To: Divide By:
%l.a. °SH 0.0225
%l.a. °D 0.0100
%l.a. °TH 0.0090
Signifi cance
of Use
Principle of
Operation