Investigating Macronutrients

• To test for the presence of starch, add iodine solution to the food sample; if starch is present, the color changes from orange to blue-black
• To test for reducing sugars, use Benedict’s Solution: add 2cm³ of the sample solution and 2cm³ of blue Benedict’s solution to a test tube, then place it in a boiling water bath for 5 minutes or until there is no further change in color
• To test for proteins, use the Biuret Test: add 1cm³ of 40% potassium hydroxide to the food sample, then add the same amount of 1% copper sulfate, shake well and observe a color change to violet if protein is present
• To test for lipids (fats and oils), perform the Emulsion Test: add 2cm³ ethanol to the food sample, shake thoroughly, then add 2cm³ de ionised water and shake; the presence of lipids is indicated by the formation of a white emulsion layer at the top of the sample
• Starch

  A) Iodine Solution

  B) Orange

  C) Blue - Black

  
• Reducing Sugars

  • If present, colour change goes from reddish-brown

  A) Benedicts Solution

  B) Blue

  C) Benedicts Solution

  
• Proteins

  A) Biuret Test

  B) Potassium Hydroxide

  C) Copper sulfate

  D) Blue

  E) Violet

  
• Lipids

  A) Emulsion Test

  B) Ethanol

  C) Deionised

  D) White

  E) Emulsion

  F) Layer