Determination of Fat content in food by Soxhlet method

What are fats ? 

• Fat is a term used to describe a class of macro nutrients used in metabolism called triglycerides.
• Fats are nutrients that give you 9 calories/1 gram. Fats help in the absorption of fat-soluble vitamins A, D, E, and K. 
• Fats are either saturated or unsaturated mainly divided in Saturated fats, Trans fat, Monounsaturated fats (MUFA), Polyunsaturated fats (PUFA) etc.

Function of fats & fatty acids in food

Fats are used in food industry for many purposes, mainly for cooking. Fats are important part of many foods like 1. dairy products (butter, cheese), 2. Confectionery (toffees – vegetable fats are added in sugar to make them chewer), 3. Meat (for marbling of meat products).

These fats acts as binding agents, flavoring agents, heating medium, textural & coloring agent & also as main source of energy.

Industrial applications of determination of fat content

• In order formulate a diet of particular individual
• In order to study quality value & attributes of food products
• To study the storage parameters of food products in Quality assurance lab because fatty foods can get rancid due to improper storage
• It is important for food producers to be able to report fat/lipids content in their products.

---

What is Soxhlet method ?

This method is widely used in food industry to analyze the fat content in food product. This also called solvent extraction method.

Equipment used – 

• Analytical balance
• Soxhlet extraction unit comprising :
  • Round bottom flask, 150 ml
  • Soxhlet extractor with 60 ml siphoning capacity and condenser
  • Cellulose extraction thimbles
• Fume cupboard
• Desiccator with silica gel desiccant
• Glass rod
• Reagents :
  • Petroleum ether/ benzene
  • Cotton wool (free of fat)

How to determine fat content ?

• Steps are following :
  1. Accurately weigh 5 gm of sample into the thimble/flask
  2. Dry the sample in an oven at 102ºC for 5 hrs
  3. Insert the thimble in a Soxhlet liquid/solid extractor
  4. Accurately weigh a clean, dry 150 ml round bottom flash and put about 90 ml of petroleum ether in the flask
  5. Assemble the extraction unit over in an electric heating mantle or a water bath
  6. Heat the solvent in the flask until it boils (Adjust the heat source so that solvent drips from the condenser into the sample chamber at the rate of about 6 drops per second)
  7. Continue the extraction process for 6 hours.
  8. Remove the extraction unit from the heat source and detach the extractor and condenser (Replace the flask on the heat source and evaporate off the solvent)
  9. Place the flask in an oven at 60 to 80ºC & dry the contents until constant weight is obtain (for 1 to 2 hr).
  10. Cool the flask in a desiccator & weigh the flask with contents.

How to calculate fat % ?

• Weight of empty flask (g) = W1
• Weight of flask and extracted fat (g) = W2
• Weight of sample = S
• formulae used :
  •  % Crude fat = (W2 – W1) x 100/S 

---

Thank You !!

Subscribe us & Inspire your inbox by our latest Content !

---