Velp Scientifica
– UDK139 Operating Manual
10004762/B5
80
10 - Kjeldahl method to determine the protein content on soya
beans and lupins
Procedure
1) Sample:
grind the sample by a suitable device. If the result is to be expressed on
dried sample, perform a separate determination of the humidity on ground sample.
Weigh 1g of sample with an accuracy of
0.1mg.
2) Reagents for digestion:
for each sample add in the test tube:
2 catalyst tablets CM (code CT0006650)
12 ml concentrated sulphuric acid (96-98%)
shake gently the test tubes
3) Digestion:
heat for 60 min at 420 °C.
4) Cooling:
let cool the test tubes to 50-60 °C.
5) Distillation-titration:
place in position the test tube with digested sample in the
unit UDK 139.
factor: 6.25
Addition of reagents:
dilution water=50ml
H
3
BO
3
=30ml
NaOH=50 ml
Titrant: HCl 0.2N
Distillation time= 4 min
Steam power= 100%
Press the button starting distillation cycle.
References:
AOAC, “Official methods of analysis”, method 979.09
267
