Test biuret

OBJECTIVE: Know the quantity of protein of  full-cream, skimmed milk, soy milk, egg white and yolk

MATERIAL: 

• 5 Beaker of 250mL
• 5 Test tubes 
• Test tube rack
• Weighing machine
• NaOH
• CuCo4
• Distilled water
• Pipet 
• Skimmed milk
• Full-cream
• Soy milk
• Egg white
• Yolk
• Spatula
• Electronic balance
• Glass stirring
• Dropper

PROCEDURE: This experiment is divided in two procedures

• Procedure 1

1. We indicate in each beaker the name of the substance that we are going to put on it, and we add 100mL of distilled water
2. We add, in one beaker, 10mL of soy milk, in another beaker 10mL of skimmed milk, in another, 10mL of full-cream, in another, 10mL of yolk and in another 10 mL of egg white
3. We stir the mixture with a glass stirring

                                     

• Procedure 2

1. We indicate in each test tube the name of the substance that we are going to put on it. This substance is going to be the mixtures that we have done in the beakers
2. We add 2mL of the substance of each beaker in one test tube
3. We put 2 mL of Na OH dissolution 20% -> 20 g of NaOH and 80 g of distilled water
4. We add 5 drops of CuCO4 1% dissolution -> 1 g of CuCO4 and 99 g of distilled water

                                        

                                  

RESULTS:

• Final colours:

• Full-cream: blue-4
• Skimmed milk: a mixture of blue and grey-5
• Soy milk: Purple-2
• Yolk: dark purple-1
• Egg white: dark blue-3

The substances are ordered depending of the quantity of proteins. The number 1 is that have more proteins and the number 5 is that have less number of proteins.