Velp Scientifica
– UDK139 Operating Manual
10004762/B5
90
20 - Kjeldahl method to determine the protein content on grain
spaghetti, macaroni
Procedure
1) Sample:
break the pasta in small pieces by hands or suitable device and mix well.
Grind finally the sample by suitable device. 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 tube with sample.
3) Digestion:
heat for 60 min at 420 °C.
4) Cooling:
let cool test tubes to 50-60 °C.
5) Distillation-titration:
place in position the test tube with sample in the unit UDK
139.
factor: 6.25
Reagents addition:
dilution water= 50ml
H
3
BO
3
= 30ml
NaOH= 50 ml
Titrant: HCl 0.1N
Distillation time= 4 min
Steam power= 100%
Press the button starting distillation cycle.
References:
AOAC, “Official methods of analysis”, method 930.25
277
