Food Tests: Detecting Nutrients in Everyday Foods

Food tests help us identify the nutrients in different food samples. Think of it like detective work in a lab—each test reveals the presence of key biological molecules.

 

Why Do We Perform Food Tests?

Food tests allow us to determine if certain nutrients, like carbohydrates, proteins, fats, or vitamins, are present in a sample. These tests use specific chemicals that react with the nutrients, often changing color to give us the answer

 

Common Food Tests and Their Results

Iodine Solution Test for Starch

• What it Tests For: Starch (a type of carbohydrate).
• Steps:
  1. Add a few drops of iodine solution to the food sample.
  2. Observe the color change.
• Result:
  • Positive Test: Turns blue-black.
  • Negative Test: Stays brown-orange.

 

 

Benedict’s Solution Test for Reducing Sugars

• What it Tests For: Reducing sugars (like glucose).
• Steps:
  1. Add Benedict’s solution to the food sample.
  2. Heat the mixture in a water bath at about 80°C for 5 minutes.
  3. Observe the color change.
• Result:
  • Positive Test: Turns brick-red (or green, yellow, or orange depending on the sugar concentration).
  • Negative Test: Stays blue

 

 

Biuret Test for Proteins

• What it Tests For: Proteins.
• Steps:
  1. Add Biuret reagent (a mixture of sodium hydroxide and copper sulfate) to the food sample.
  2. Observe the color change.
• Result:
  • Positive Test: Turns purple.
  • Negative Test: Stays blue.

 

 

 

Ethanol Emulsion Test for Fats and Oils

• What it Tests For: Fats and oils (lipids).
• Steps:
  1. Mix the food sample with ethanol and shake well.
  2. Add water and shake gently.
  3. Observe for cloudiness.
• Result:
  • Positive Test: A white, cloudy emulsion forms.
  • Negative Test: The solution remains clear.

 

 

 

DCPIP Test for Vitamin C

• What it Tests For: Vitamin C.
• Steps:
  1. Add a few drops of DCPIP solution (blue) to the food sample.
  2. Observe the color change.
• Result:
  • Positive Test: Turns colorless.
  • Negative Test: Stays blue.