In the early days, it was not possible to determine the quantity of butterfat in milk. Unscrupulous farmers watered down their milk and scooped off cream to increase their volumes.
They ended up with more money while the honest farmers earned less since they did not water down their milk.
Following these challenges, Professor Stephen Babcock of the University of Wisconsin developed a non-solvent wet extraction method, which became known as the Babcock method of butterfat determination.
While conducting experiments, he had found that when he added concentrated sulphuric acid (92% or S.G 1.82) to 18 g/17.6 ml of milk, the butterfat would separate out.
It would then be easy to determine the volume of the butterfat by subtracting it from the initial volume of milk used.
The Babcock rapidly became popular, as farmers could easily determine the quality of their milk. They were even able to select animals that produced high quality milk for breeding.
The Principle of the Babcock Method
It uses the same principle as the Gerber method. Sulphuric acid dissolves all the milk solid non-fat (MSNF), which facilitates separation of fat.
Centrifuging at 50°C improves the separation and maintains the butterfat in a liquid state for easy reading of the volume.
Determination of butterfat content is done in a specially graduated Babcock test tube. The volume is expressed as %w/w milk.
The whole test takes about 45 minutes to finish.
Apparatus and Materials for the Babcock Method
- Babcock sulphuric acid (92% or S.G. 1.82-1.83)
- Glassware (17.6 ml pipette, 8% milk bottles, 50% cream bottles, 50% Paley bottles, 17.5 ml cylinders).
- Babcock shaker.
- Torsion balance, 9 and 18 g weights.
- Water bath at 50°C.
- Babcock centrifuge.
- N-butyl alcohol
Determining Butterfat Content of Milk by Babcock Method
- Temper milk sample to 20°C and mix thoroughly to obtain a homogeneous sample.
- Pipette 17.6 ml of milk into the 8% bottle. Blow out the last drop into the bottle.
- Add 17.5 ml Babcock acid incrementally into the milk sample and mix thoroughly to obtain a chocolate brown color.
- Put the sample into the centrifuge and run for 5 minutes.
- Adjust the volume of the mix to three quarters of the bulb (below the neck) by adding distilled water at 60°C. Ensure you do not mix it.
- Put the adjusted mix into the centrifuge and run for 2 minutes.
- Add more water at 60°C until the fat floats in the neck of the bottle. Ensure the meniscus is within the graduated section. Again, do not mix.
- Run the adjusted mix in a centrifuge for a further 1 minute.
- After centrifuging, temper the bottle in a water bath at 50°C for about 5 minutes.
- Read the butterfat content off the graduated section.
Determining Butterfat Content of Cream and Cheese by Babcock Method
- Grind cheese into fine particles. Temper both cream and cheese to about 20°C and mix.
- Weigh 9 g of cream (or cheese) into 50% cream bottle (Paley bottle for cheese sample) and add 9 ml of distilled water at 20°C (10 ml of distilled water at 60°C for cheese sample).
- Add 17.5 ml Babcock acid incrementally and mix after each addition until all the contents dissolve resulting into a chocolate brown solution in case of cream and all the cheese dissolve.
- Centrifuge the resultant mix for 5 min.
- Add distilled water at 60°C to bring the volume of the bulb to about three quarters. Unmixed, send to the centrifuge and run for 2 minutes.
- Add more water at 60°C to bring the fat into the neck of the bottle. Again, unmixed, send to the centrifuge and run for 1 minute.
- Temper the bottle in a water bathe at 50°C for 5 minutes.
- Add 4-5 drops glymol on the fat column and let the drops run down the side of the bottle. They will demarcate the length of the fat column.
- Read the fat content from the graduated section of the bottle. Express as percent weight.
Determining the Butterfat Content of Skim milk, Buttermilk, and Whey by Butterfat Content
- Temper the sample to 20°C and mix gently.
- Transfer 2 ml N-butyl alcohol into the 18 g double neck bottle followed by 9 ml of the sample. Swirl the mix gently to obtain a homogeneous mix.
- Once you have the homogeneous mix, add 9 ml of Babcock acid into the sample of skim milk or buttermilk (add 7 ml in case of whey sample whey).
- Place the sample bottles into the Babcock centrifuge with the small neck facing outside. Run the centrifuge for 6 minutes.
- Adjust the contents of the bottle to just 1 cm below the neck by adding water at 60°C. Unmixed, centrifuge the mix for 2 minutes.
- After centrifuging, temper the sample bottles in water bath at 50°C for 5 minutes.
- Place your finger over the neck and press down until you can read the lower meniscus on a major division. Read the butterfat content of the graduated section.
Advantages of the Babcock method
- The Babcock method is very rapid.
- Its accuracy is undisputed
- It is a cheaper method of butterfat determination.
Limitations of the Babcock method
- It is not possible to determine the quantity of phospholipids
- Due to the high acid concentration, this method is unsuitable for products with sugar or chocolate. The acid has an adverse effect on the sugars or chocolate.