Practise 4. Determination of proteins and reaction of the biuret

To determine the presence of proteins we will realize two experiments:
Xantoproteinc reaction:

1- Extract some olive seeds chopping the stones.

2- We leave them drying for one week.

3- We take the dry olive seeds and we mince them in a container.

4- Minced we throw them in a test tube and we add 1 cm3 of nitric acid (HNO3) concentrated.

5- We heat the test tube with a lihgter. If there are proteins, they will react with the HNO3 and the sample will become yellow.

Reaction of the biuret
The name of the reaction is bacause of when the proteins get in contact with blond it produces a substance called biuret.

1- We get some dry seeds of olives and we grind them in a container.

2- When they are grind we put them in a test tube and we add 1 cm3 of sodic hidroxide in a 20%. In case that there are proteins, it would produce biuret.

3- Then we add some drops of sulfato cuprico mixed in 1%.

4- If the proof turns into a violet colour it would be because the biuret has react with the sulfato cuprico, showing that there are proteins.