Velp Scientifica
– UDK139 Operating Manual
10004762/B5
105
34 - Determination of the volatile acidity of tomato paste
The volatile acids are measured ,in the presence of phenolphthalein indicator, in the
distillate obtained by steam distillation of a proper amount of sample.
NOTE:
in order to peform this kind of analysis it is necessary to substitute the
techno-polimer splash-head on the distillator with the new glass splash-head , code
A00000216.
Procedure
1) Reagents:
For the steam generator use distilled or deionised water boiled for some minutes in
order to eliminate the carbon dioxide. Use the same kind of water to dilute the
sample and for the distillate collecting flask.
crystallized tartaric acid
phenolphthalein, 1% hydro-alcoholic solution
sodium hydroxide (NaOH), 0.1N solution
VELP weighing boats, code CM0486001
2) Sample:
weigh 20g of sample by the VELP weighing boats and introduce in the test tube. The
use of the weighing boats avoids errors during the sample weighing, permitting to
transfer completely the sample to the test tube for the analysis.
As an alternative, the following amount of sample can be used:
600/R g, weighed with a tolerance margin of 0.01g; R is the content of NTSS
(natural total soluble solids, or soluble dry matter of the sample).
Afterwards introduce in the test tube containing the sample 0.1g of tartaric acid and
then place in the distillator the test tube.
3) Distillation:
analytical parameters:
H
2
O = 50ml (distilled or deionized and boiled). NaOH = 0ml. H
3
BO
3
= 0ml.
Take off the distillate collecting tube from the condenser and place a new silicon tube
in the same position.
Place in position on the mobile round stand of the distillator an Erlenmeyer flask
(250ml) containing 40ml of deionised or distilled water boiled for some minutes. Be
sure that the end of the silicon tube, which is connected to the condenser, is
completely dipped in the water.
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