Page 65 - Feed Lab

Estimation of Crude Protein- Macro Kjeldhal Method Suguna Management System Ver 1.0 / SOP / FQL / P2 - 03 Page 3 of 3

FAdd about 100 ml of 40% sodium hydroxide FFor recovery, take 0.25 gm urea AR and do same
through the dropping funnel and careful to close. digestion as per crude protein. It should be 100% ±
(Picture-16)

FHeat gently to boil and collect solution up to 200ml.
The ammonia gas neutralized in the standard
sulphuric acid. (Picture-17)

FThe un neutralized 0.5 N sulphuric acid is back
titrated with standard 0.25 N sodium hydroxide
using methyl red indicator. The end point is the
change of colour from pink to yellow. (Picture-18)

FFrom the titre value, the percentage of protein is
calculated by doing a blank and recovery.

FFor blank, do all the points without sample. It always
should be zero titre value.

CALCULATION
(Blank - TV) X N.of NaoH X 1.401 X 6.25
Crude Protein % =-------------------------------------------------------
Sample Weight, g

Picture -11 Picture-12 Picture-15 Picture-16

Picture-13 Picture-14 Picture-17 Picture-18

REFERENCE:
1. Bureau of Indian Standard IS 7874 1975
2. Association of Official Analytical Chemist 2000.

Prepared by : Approved by :
53 Director - Technical