SOP: Determination of Fat Content in Condensed Milk (Gerber)

GIFSQ — Global Institute for Food Safety & Quality

Scope

This method is applicable to all dairy products and food and food products such as sweetened condensed milk, skim condensed milk as well as other food products.

1. Principle

When sulfuric acid is added to the milk, the protein will be digested, thus destroying the membrane of the fat globules. The free fat is then released. The fat remains in liquid due to the heat produced and during centrifugation, the fat being lighter will be separated on the top of the solution. Addition of amyl alcohol has the function of separating fat from the complexes.

2. Apparatus

a. Milk butyrometer (Gerber 0–10 scale)

b. Milk pipette, with stopper and key

3. Reagents

a. Gerber sulfuric acid

b. Amyl alcohol

4. Procedure

Measure 10 mL sulfuric acid into a milk Gerber butyrometer

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Fill the milk pipette with prepared milk sample and run the milk into the butyrometer tube slowly

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Add 1 mL of amyl alcohol

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Add some water to make volume

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Close with a stopper and shake until homogeneous, inverting for the complete admixture of the acid

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Keep in the water bath if temperature adjustment is not available in the centrifuge

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Centrifuge for 5 minutes at 1100 rpm

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Remove the butyrometer tube and read off the percentage of fat, adjusting the height in the tube as necessary by moving the stopper slowly with the key

5. Calculation

The reading of fat in the butyrometer is the fat percentage of the sample. For a diluted sample, multiply with the dilution factor:

% Fat = (Actual reading ÷ Percentage of solution) × 100

(For the standard prepared solution — 100 g made to 500 mL, a 20% solution — the factor is × 5.)

References

Laboratory Catalogue for Milk Analysis, Funke Gerber, Method 3.4, page 20.