Babcock Methods for Milk Fat

Apparatus and Materials

  1. Babcock centrifuge.
  2. Water bath at 55C.
  3. Torsion balance, 9 and 18 g weights.
  4. Babcock shaker.
  5. Glassware: 8% milk bottles, 50% cream bottles, 50% Paley bottles, 17.5 ml cylinders, 17.6 ml pipette, .
  6. Reagents: - Babcock sulphuric acid (Sp. Gr. 1.82-1.83)
  • N-butyl alcohol
  • Glymol.

Milk

  1. Temper sample to 20C and mix by pouring gently from original container to a beaker of similar capacity 4-5 times.
  2. Transfer 17.6 ml (18.0g) of milk to 8% bottle with 17.6 ml pipette. Allow pipette to drain then blow out the remaining drop into the bottle.
  3. Add 17.5 ml sulphuric acid (Sp. Gr. 1.82-1.83) in at least three increments using special cylinder. Rotate bottle between thumb and fingers while adding acid to wash milk from neck. Mix thoroughly 2 min. after each addition of acid by moving the bulb of the bottle in rapid circular motion. Final colour of mixture should be chocolate brown.
  4. Centrifuge 5 min.
  5. Add distilled water at 60C to bring contents to within one-quarter inch of base of neck. Do not mix.
  6. Centrifuge 2 min.
  7. Add water at 60C to float fat into neck of bottle. Top meniscus should be about even with the top of the graduated portion. Do not mix.
  8. Centrifuge 1 min.
  9. Temper bottles in water bath at 55C for 5 min.
  10. Measure length of fat column with dividers from top of upper meniscus to bottom of lower meniscus. Place one divider point at zero mark and read percentage fat by weight directly where other point touches the scale.

Cream and Cheese

  1. Temper cream sample to 20C and mix. Grind cheese to small particles.
  2. Weigh 9 g of cream into 50% cream bottle and add 9 ml of distilled water at 200C. Weigh 9 g of cheese into a 50% Paley bottle and add 10 ml of distilled water at 60C.
  3. Add 17.5 ml sulphuric acid in at least three increments. Mix until colour is uniform chocolate brown and all cheese particles are dissolved.
  4. Centrifuge 5 min.
  5. Add distilled water at 60C to bring contents to within one-quarter inch of base of neck. Do not mix.
  6. Centrifuge 2 min.
  7. Add water at 60C to float fat into neck of bottle. Do not mix.
  8. Centrifuge 1 min.
  9. Temper bottles in water bat at 55C, for 5 min.
  10. Place 4-5 drops glymol on the fat column letting these run down the side of the neck. Measure the length of the fat column from the demarcation between fat and glymol to the bottom of the lower meniscus.
  11. Report fat in percent by weight.

Skim milk, Buttermilk, Whey

  1. Temper sample to 20C and mix gently.
  2. Transfer 2 ml N-butyl alcohol and then a 9 ml sample to an 18 g double neck bottle. Mix thoroughly with a circular motion.
  3. Add 9 ml of Babcock sulphuric acid for skim milk or buttermilk, 7 ml for whey.
  4. Centrifuge 6 min. Place bottles in the centrifuge cup with the small neck facing the outside.
  5. Add water at 60C to bring contents 1 cm from the base of the neck. Do not mix. Centrifuge 2 min.
  6. Temper bottles in water bath at 55C for 5 min.
  7. Place a finger over the large neck and press down until the lower meniscus of fat in the small neck corresponds to a major division.