Dear researchers,
We did the Gerber fat test for milk and sausage, after reacting with acid, the material turns brown and dark purple. What is the exact cause of this color change?
90% sulfuric acid is used for milk and Salvin reagent is used for sausage.
Is it because of antioxidants and nitrite or are proteins involved? Or is it a combination of these things?
Dear Helia
In the Gerber test H2SO4 is used to increase specific gravity of milk serum which makes greater difference between milk serum and fat globules. It also destroys stickiness of milk by dissolving chemical bonds (hydrogen bounds first).
Adding sulfuric acid will denature the casein. As a result, the casein molecules are likely to stick to each other and form a centrifugable pellet that goes to t,he bottom of a centrifuge tube after spinning.
Sulfuric acid is very reactive and dissolves most metals, it is a concentrated acid that oxidizes, dehydrates, or sulfonates most organic compounds, often causes charring.
You can try out this one (think of personal safety and protection): take a lump of sugar and put 2-3 drops of 91% sulfuric acid and watch. The sulfuric acid is extracting all the water and leaving a black, charred residu.
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