Extraction And Determination Of Crude Fat From Plant And Animal Tissues

Ms. Nadia Amara

Introduction of Crude Fat :

Determination of Crude Fat is the term used to refer to the crude mixture
of fat material present in a sample.

Crude fat is the traditional measure of fat in food products.

Fat is important to all aspects of meat production and processing.

Lipids/fats are relatively non-polar molecules, they can be pulled out of a
sample using relatively non-polar solvents. (With a non-polar solvent, only
non-polar molecules in the sample dissolve while polar ones do not ).

The lipid materials may include triglycerides, diglycerides, monoglycerides, phospholipids, steroids, free fatty acids, fat soluble vitamins, carotene pigments, chlorophylls, etc.

Crude fat content is determined by extracting the fat from the sample using
a solvent, then determining the weight of the fat recovered.

The common approach for total crude fat determination is based on the
solubility of lipids in non-polar organic solvents such as hexanes, petroleum
ether, or other non-polar solvent .

In this lab we will determine the crude fat extracted by petroleum ether
solvent .

This method is applicable to extractions of oilseeds, meats, feeds, and foods.

Calculation :

Crude Fat % ( % of Dry matter) = (weight of crude fat + weight of extraction
flask )-(weight of extraction flask) / weight of sample *100

Principle of Soxhlet extraction :

Soxhlet extraction is a continuous solid / liquid extraction.

A solid which contains the material to be extracted is placed in what is called a thimble.

A thimble is made out of a material which will contain the solid but allow liquids to pass through. A lot like filter paper.

The thimble containing the material is placed in the Soxhlet extractor.

An organic solvent is then heated . As it boils its vapors rise up and are
condensed by a condenser. The condensed solvent then fills up the thimble,
and after it fills with enough solvent it automatically siphons back down
into the container of organic solvent.

This process takes place over and over again until all the material to be
extracted from the solid in the thimble is now extracted into the organic
solvent.

This cycle may be allowed to repeat many times, over hours or days.

The advantage of this system is that instead of many portions of warm solvent being passed through the sample, just one batch of solvent is recycled.

After extraction the solvent is removed, typically by means of a rotary evaporator, yielding the extracted compound. The non-soluble portion of the extracted solid remains in the thimble, and is usually discard.

1: Stirrer bar/anti-bumping granules

2: Still pot (extraction pot) – still pot should not be overfilled and the volume of solvent in the still pot should be 3 to 4 times the volume of the soxhlet chamber.

3: Distillation path

4: Soxhlet Thimble

5: Extraction solid (residue solid)

6: Syphon arm inlet

7: Syphon arm outlet

8: Reduction adapter

9: Condenser

10: Cooling water in

11: Cooling water out

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In this experiment we determined the fat content of cips sample. We used some apparatus and suitable organic solvent for fat determination. Organic solvents can be used to extract fat from food products. Many fat methods are based on extracting the fat with these organic solvents.Fat content is important for food products.

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FAT DETERMINATION THEORY

Lipids are a family of naturally occurring compounds grouped together on the basis of their relative insolubility in water and solubility in nonpolar solvents. These are naturally occurring molecules that can be isolated from cells and tissues by extraction using nonpolar organic solvents.There are two classes of

i) those with ester linkages that can be hydrolysed, for example, fats and waxes

ii) those without ester linkages and so cannot be hydrolysed, for example, cholesterol and steroids.

Fats and oils are triacylglycerols. They are triesters of glycerol (propane-1,2,3-triol) with three long chain carboxylic acids. Reaction with aqueous sodium hydroxide yields glycerol and the three fatty acids. Fatty acids are usually unbranched and contain an even number of carbon atoms, usually from 12 to 20. If there are any double bonds, they tend to have cis geometry. Fats containing one double bond are monounsaturated and those with more than one double bond are polyunsaturated.Saturated fats have a uniform shape that allows them to pack together in a crystal lattice. Unsaturated fats have double bonds that introduces kinks into the hydrocarbon chain making crystal formation more difficult. This is why saturated fats have higher melting points and are solids at room temperature compared to unsaturated fats that tend to be liquids (oils).The most abundant lipid in olive oil is glyceryl trioleate, a triester formed from glycerol and oleic acid, a mono-unsaturated fatty acid with a cis double bond in the middle of the C18 chain
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