Determination of Ether Extract/Fat

The dried feed sample is dissolved with petrol ether and then the ether
is evaporated in the Soxhlet apparatus. The residues are crude fat.
In the Animal Nutrition Laboratory at ICARDA a Soxtherm apparatus
from Gerhardt GmbH is used. The procedure described below follows
the instruction for this specific Soxhlet apparatus. In the laboratory the
modified method for determination of fat in meat has been adapted.
Procedure
• Fill extraction beakers with boiling stones dried at 103 °C (Fig. 14)
• Cool beakers down to room temperature in desiccator
• Weigh beakers on precision balance (W0)
• Weigh 5 g of dried samples in extraction thimbles (Ws)
• Cover with fat free cotton
• Insert extraction thimble into extraction beaker
• Add 140 ml of petrol ether and insert beaker in Soxhlet apparatus

• Start program
• Program:
1. Boiling time 30 min
2. Solvent reduction 5×15 min
3. Extraction time 80 min
4. Extraction temperature 150 °C
5. Solvent reduction 8 min
6. Solvent reduction 5 min
7. Solvent reduction interval 3 min
8. Solvent reduction phase 3 sec
• After termination of program, dry beakers at 105 °C overnight
• Cool beakers down to room temperature in desiccator and weigh
(We).
Calculations
%Crude fat = [(We–W0 )/(Ws×%DM)]×100
Reagents / Solutions
Petrol ether (40–60 °C)
Equipment
• Precision balance
• Soxhlet (Soxtherm S306 A, Gerhardt GmbH, Germany)
• Air-circulation oven
• Extraction beakers with boiling stones
• Extraction thimbles
Reference
• Undersander D, Mertens DR and Thiex N. 1993.
• AOAC. 1995.
• Instruction Manual Soxtherm S306 A. 2000.