Determination of fat in milk

Determination of fat in milk

• 1.
  DETERMINATION OF FAT INMILK  METHOD-1 - GERBER METHOD
• 2.
  Gerber tube (butyrometer) Centrifugefor Gerber method Sulphuric acid Iso-amyl alcohol Pipette
• 3.
  Water bath forbutyrometer Lock stopper and key for butyrometer
• 4.
  REAGENTS AND APPARATUS 1.Sulphuric acid (density- 1.812g/ml, concenration-90-91%) 2. Iso-amyl alcohol (0.818g/ml, furfural free) 3. Gerber butyrometer- 6, 8 and 10 percent 4. Pipette- 10ml for sulphuric acid 5. Pipette- 10.75ml for milk 6. Pipette- 1ml for iso-amyl alcohol 7. Lock stoppers for butyrometer 8. Lock stopper key 9. Water-bath 10.Gerber-Centrifuge
• 5.
  METHOD • The milkis mixed with sulphuric acid and iso-amyl alcohol in a Gerber tube, permitting dissolution of protein and release of fat • The tubes are centrifuged and the fat rising into calibrated part of the tube is measured as percentage of fat content of milk sample • This method is suitable as a routine or screening test
• 6.
  WATER-BATH  Water-bath shallbe made of suitable material (stainless steel)  Capable of being maintained at 65 ± 2º C temperature  Shall have sufficient depth to support butyrometer in vertical position with their scale completely immersed  The bath shall be fitted with horizontal perforated plates to hold the butyrometers  Shall also carry suitable thermometers
• 8.
  GERBER-CENTRIFUGE  The centrifugemay be hand driven or electric driven  Shall be capable of producing within 2 min when fully loaded, a relative centrifugal acceleration of 350 ± 50 gn at the outer end of butyrometer stopper
• 9.
  PROCEDURE  Measure 10ml of sulphuric acid in butyrometer tube without wetting the neck of butyrometer  Run the milk sample into butyrometer tube along the side wall without wetting the neck  Add 1 ml of iso-amyl alcohol, close with the lock stopper, shake until homogenous, invert it for complete admixture of the acid  Keep in a water bath for 5 minutes at 65 ± 2º C  Centrifuge for 4 minutes at 1100 rpm  Allow the centrifuge to come to rest  Remove the butyrometer tubes and place in water bath for 5 minutes
• 10.
  PROCEDURE  Read thepercentage of fat after adjusting the height in the tube as necessary by movements of lock stopper with the key  Note the scale reading corresponding to the lowest point of the fat meniscus and the surface of separation of fat and acid  When readings are being taken, hold the butyrometer vertical, read the butyrometer to the nearest half of the smallest scale division
• 12.
  NOTE  Butyrometer mustalways be emptied without delay and highly acidic waste dispose off completely  Tubes must be cleaned with chromic acid  In homogenized milk, fat separates with more difficulty and centrifuging more than once may be required  In case of old samples, the concentration of sulphuric acid may be increased to facilitate better dissolution