Gerber Test for Fat % in Raw Milk
2013
Gerber Test for Fat % in Raw Milk
Fat is the mass fraction of substances determined according to this procedure
and is expressed as percentage by mass. This method is applicable to raw and
pasteurized milk.
Procedure
1. Add 10 ml of Gerber sulfuric acid :( specific gravity 1.823) at 15-21c into Gerber
Butyrometer .
2. Add 1ml of isoamyl alcohol and insert the lock stopper grasp the test bottle at
the graduated column and shake it until the curd is completely digested.
3. Adjust temperature of the milk sample to 22-21C°.
4. Transfer 11ml well mixed milk sample to Gerber test bottle.
5. Place them in a Gerber centrifuge close the cover and lock. After the required
speed 1500 rpm centrifuge for 5mint stop the centrifuge.
Principle or mechanism of test
Both the milk and Gerber sulfuric acid are mixed to produce an exothermic
reaction that disintegrates the emulsion structure in milk (i.e. the acid produces
necessary heat to complete digestion of the non fatty materials)
The exothermic reaction in combination of the isoamyl alcohol releases the
liquefied fat for measurement and prevents charred milk fat. The free fat is
collected in the graduated portion of the neck of the Gerber
bottle .
* Gerber sulfuric acid + milk sample = exothermic reaction and digestion of solid
non fatty materials
* Exothermic reaction + isoamyl alcohol =liquefied fat and prevent charred milk
fat
* Gerber centrifuge
2013
Gerber Test for Fat % in Raw Milk
Table (1) the minimum Fat% in different animal species.
Animal species
minimum fat% in milk
Cows
Buffalo
Sheep
Goat
%3
%5
%4
% 5.5
Purpose of Gerber test
1-Detect the Adulteration
(Causes of decrease fat %)
* Add water to the milk
* extract or remove the fat from the milk (skim milk)
*The agitation is not perfect
* The milking did not include the last drop which contains the last drop of fat.
2- Calculate the total solid and total not fatty material and protein by having the
fat% and using some equations