SOP: Determination of Fat Content in Butter (Gerber)

GIFSQ — Global Institute for Food Safety & Quality

1. Principle

When sulphuric acid is added to butter, the proteins will be digested, thus destroying the membrane of the fat globules. The free fat is then released. The fat remains in liquid due to 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 other components.

2. Apparatus

a. Butter butyrometer, 70 to 100% range, with stopper funnel

b. Balance

c. Gerber centrifuge, 1100 ± 100 rpm

d. Water bath, 65 ± 2°C

3. Reagents

a. Sulphuric acid with a density of 1.807 to 1.812 g/mL at 27°C, corresponding to a concentration of sulphuric acid from 90–91% by weight

b. Amyl alcohol for milk testing (furfural free)

4. Procedure

Weigh 5 g of well mixed butter sample into the butter butyrometer

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Add 10 mL of Gerber sulphuric acid

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Add 1 mL iso-amyl alcohol to the butyrometer and adjust the level up to the top graduated scale mark by adding hot distilled water

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Close the butyrometer with the rubber stopper and mix the contents well by inverting the butyrometer at least ten times

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Centrifuge for five minutes, then place the butyrometer in the water bath at 65°C

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Adjust the fat column and read the fat percentage

References

Laboratory Catalogue for Milk Analysis, Funke Gerber, Method 3.13, Page 22.