P9. Protein identification

Introduction:


We will identify proteins and look at what foods carry more. So use the Biuret reagent.

Objectives:

1. Identify peptide bonds
2. Compare protein concentration in different foods

Hypothesis:

• The egg white proteins have more than yogurt, which have more protein than milk, which have more protein than potatoes. Rice milk and yolk have not proteins.

Materials:

• 7x250 mL beaker
• 6 test tubes
• Test tube rack
• 6x10 mL pipet
• Mortar
• Glass marking pen
• Gloves
• Goggles
• Milk
• Soy Milk
• Egg
• Yogurt
• Potato
• Distilled water
• NaOH 20%
• 10 drops of CuSO4

Procedure:

Take 10 mL of normal milk (M), rice milk (RM), egg white (EW), yolk (EY), yogurt (Y) and potato (P)., And put in a test tube (each food in a different tube).
Put 2 mL of 20% NaOH.
Let CuCO4 5 drops of each tube.
Hopefully 5 minutes.
Comparing the tubes: the more purple, more protein.

Conclusions and coments:

These are the results of practice. (proteins are sorted from most to least):

EY: -
EW: 1
M: 3
RM: -
P: 4
Y: 2

Questions:

1- Which food has proteins?
Eggwhite, milk yogurt and potato, animal food.

2- Which food has more proteins? Why?
Eggwhite because it's animal food and it's rich in proteins. 

3-Do you find any difference between rice milk and cow milk?
Rice milk doesn't have proteins however cow milk does as i had said before.

4- Is there any difference among milk and yogurt? why?
Yes, yogurt has more protein than milk because the protein is more concentrated than in the milk, it has less water.