Food Science Experiment- Crude Fat Analysis

Posted by Buddhi Katangodage

 

Introduction of Crude Fat

Fat is important to all aspects of meat production and processing. Crude fat content is determined by extracting the fat from the sample using a solvent, then determining the weight of the fat recovered. As 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. Problems arise however, in cases where lipids are bound in animal or plant cell membranes. Animal and plant cell membranes are made up of molecules that have both polar and non polar regions such as triglycerides (molecule with polar glyceride heads and non-polar fatty acid tails) and phospholipids (similar to triglycerides, but a phosphate group replaces the fatty acid tail). These molecules end up grouping together with their polar heads sticking outwards and non-polar tails inwards making it difficult for non-polar solvents to interact with the non-polar tails and extract them. 

Equipments

• Analytical balance (at least 1 mg sensitivity).
• Electrical drying oven to be operated at 105ºC± 1ºC.
• Soxhlet extraction unit comprising:
  − Round bottom flask, 150 mL
  − Soxhlet extractor with 60 mL siphoning capacity and condenser.
  − Cellulose extraction thimbles (28 x80 mm)
  -Heat source, either electric heating mantle, or steam bath 100 mL beaker
  -Desiccator with silica gel desiccant 

Reagents

• Petroleum Ether(boiling point: 40-60ºC)

Method

1. Weigh 2-3g of the dried food sample into extraction thimble.
   
2. Place the thimble inside the Soxhlet Apparatus.
3. Connect a dry pre-weighted solvent flask beneath the apparatus and add required quantity of solvent and connect the condenser.
4. Adjust the heating rate to give a condensation rate of 2-3 drops and extract for about 16hours.
5. After completing the extraction, remove the thimble and reclaim ether using the apparatus.
6. Complete the removal of ether on a boiling bath and dry flask at 105ºC for 30 mins.
7. Cool in a desiccator and weigh.
   

 

Soxhlet Extraction Apparatus

 

Soxhlet Extraction Apparatus Labelled Diagram

Calculation

Crude Fat( % of Dry matter) = (weight of fat (x)/ weight of sample (w))*100

Advantages

• Inexpensive equipment usage
• Filtration Not required
• Continuous contact with the solvent
• Possibility of extracting more sample mass than the other methods available
• Wide industrial application and efficient

Disadvantages

• Relatively slow extraction(24-48 hrs)
  
• Large amount of solvent is needed (350-500ml)
• Some solvents create environmental problems such as toxicity