Methodology for Lipids

Estimation of oil in oilseeds


 
Fats and fatty acid esters of glycerol. Fat as liquid is called oil. Seeds like gingely, groundnut, castor, sunflower etc. contain oil as reserve food material for the embryo.




Principle

Oil from a known quantity of the seed is extracted with petroleum ether. It is then distilled off completely, dried, the oil weighed and the % oil is calculated.




Material
» Petroleum Ether (40-160°C)
» Whatman No. 2 Filter paper
» Absorbant Cotton
» Soxhlet Apparatus


Procedure
1.

Fold a piece of paper in such a way to hold the seed meal. Wrap around a second filter paper which is left open at the top like a thimble. A piece of cotton wool is placed at the top to evenly distribute the solvent as it drops on the sample during extraction.

2.

Place the sample packet in the butt tubes of the Soxhlet extraction apparatus.

3.

Extract with petroleum ether (140 drops/min) for 6h without interruption (for castor beans use hexane) by gentle heating.

4.

Allow to cool and dismantle the extraction flask. Evaporate the ether on a steam or water bath until no odor of ether remains. Cool at room temperature.

5.

Carefully remove the dirt or moisture outside the flask and weigh the flask. Repeat heating until constant weight is recorded.



Calculation
Oil in ground sample % =

Weight of oil (g)

X 100

Weight of sample (g)


Oil to dry weight basis =

% oil in ground sample

100% moisture in whole seed

 
Note
Sample Preparation:
Sample preparation varies depending upon the materials. Peanut
Place about 50g of kernels in a drying dish and dry at 130°C for not more than 20min in a forced draft oven. Cool to room temperature and then pass through the nut slicer. Care is to be taken to prevent expressing of any oil while slicing. Mix the sliced sample well. Weigh accurately 2g into the filter paper fold.

Sunflower
Weigh about 50g of sunflower seeds into a large beaker. Add an equal weight of Hyflow supercel or equivalent (dried at 130°C overnight before use). Mix well. Grind the mixture immediately.
For sunflower seeds oil in ground sample, % =

Weight of oil (g) x 200

Weight of sample (g)

since equal quantity of Hyflow supercel is added.  
Soyabean
Dry the sample well either by keeping overnight in a warm room or in an oven so that the moisture is within 6-8%. Grind in a micro-sample mill with minimum exposure to air. Mix thoroughly. Weigh exactly 2g of the sample and place in the filter paper fold.  

Castor Bean
Dry the sample as for peanuts. Cool to room temperature and then grind through the food chopper, feeding the beans slowly to prevent expression of oil. Mix and weigh 5g into the filter paper fold. 

Cotton Seed

Dry about 60g of sample for 2h at 130°C in a forced-draft oven. Place the dried seed in the prepared vessel and cover with a clay lid. Place the vessel in an oven for 1h. the temperature can be up to 115°C. Grind the sample by rapid feeding through the mill. Mix well and weigh 4-5g into the filter paper fold. 


Safflower

Weigh accurately 10g whole seed and pulverize in an iron mortar. Transfer into the filter paper fold. Wash mortar and pestle carefully with petroleum ether and pour washing into the filter paper fold.