Chapter 3 part 2: Food tests 🌯🧪

Question 1

What is the benedict’s test?

Answer 1

• The benedict’s test is testing for reducing sugars.
  The procedure of the benedict’s test:
  1. Add an equal volume of benedict’s solution to the sample in a test tube.
  2. Shake the mixture to combine both mediums and substances together.
  3. Place in a boiling water bath for 2-3 minutes.
  4. Observe the contents in the test tube.
  **RESULTS AND CONCLUSIONS TO THE TEST:
  1. Result: The solution remained blue.
  Conclusion: Reducing sugars are absent.
  2. Result: A green precipitate is formed.
  Conclusion: A trace amount of reducing sugars is present.
  3. Result: A yellow/orange precipitate is formed.
  Conclusion: A moderate amount of reducing sugars is present.
  4. Result: A red precipitate is formed.
  Conclusion: A large amount of reducing sugars is present.

Question 2

What is the iodine test?

Answer 2

• The iodine test is testing for starch. (presence or absence of starch)
  The procedure of the iodine test:
  1. Add a few drops of iodine solution to the sample.
  **RESULTS AND CONCLUSIONS TO THE TEST:
  1. Result: The iodine remained brown.
  Conclusion: starch is absent.
  2. Result The iodine turned from brown to blue-black.
  Conclusion: Starch is present.

Question 3

What is the emulsion test?

Answer 3

• The emulsion test is testing for fats.
  The procedure for a liquid sample:
  1. Add 2cm3 of ethanol to a drop of the sample in a test tube.
  2. shake the mixture.
  3. Add 2cm3 of water and shake the mixture.
  The procedure for a solid sample:
  1. Crush the sample into small pieces and place the pieces in a test tube.
  2. Add 2cm3 of ethanol.
  3. Shake the mixture.
  4, Let the solid particles settle down to the bottom.
  5. Decant ethanol into another test tube with 2cm3 of water.

(Not sure):
**RESULTS AND CONCLUSIONS for a LIQUID sample:
1. Result: The mixture remained clear
Conclusion: Fats are absent.
**RESULTS AND CONCLUSIONS for a SOLID sample:
1. Result: A white emulsion is formed
Conclusion: Fats are present.

Question 4

What is a biuret’s test?

Answer 4

• The biuret’s test is testing for proteins.
  The procedure for the biuret’s test:
  1. Add 2cm3 of biuret solution (this solution is made of sodium hydroxide and copper (II) sulfate) to 2cm3 of the sample.
  2. Shake the mixture stand for 5 minutes (minimum?)
  **RESULTS AND CONCLUSIONS TO THE TEST:
  1. Results: The mixture remained blue.
  Conclusion: Proteins are absent.
  2. Results: The mixture turned from blue to violet.
  Conclusion: Proteins are present.