FOOD TESTING LABORATORY

Human bodies require essential nutrients such as carbohydrates, proteins, fats, vitamins, and minerals. To identify which nutrients are present in our everyday food, we can conduct food tests using specific chemical solutions called reagents (indicators).

 Visual Guide to Food Test Reactions

🍬 A. Glucose Test (Benedict's Test)Purpose: Detects reducing sugars (like glucose).

Special Requirement: The mixture must be heated in a boiling water bath for a few minutes.
Color Progression: The final color indicates the concentration of glucose:

Blue: Negative (No sugar).
Green / Yellow: Trace/Low sugar amount.
Orange: Moderate sugar amount.
Brick Red: Positive high (Abundant sugar concentration).


🥚 B. Protein Test (Biuret Test)

Purpose: Detects peptide bonds which indicate the presence of proteins.
Reagent: Biuret solution (a mixture of Sodium Hydroxide/NaOH and Copper Sulfate/CuSO₄).

Light Blue (Initial Color): Represents a negative result.
Purple / Violet (Final Color): Confirms a positive result for protein. A deeper purple color signifies a higher protein content.


🍞 C. Starch Test (Lugol's / Iodine Test)

Purpose: Identifies complex carbohydrates (starch/amilum).
Procedure: Drop the Lugol/Iodine solution directly onto the crushed food sample. No heating required.

Result:

Positive (+): Turns dark blue, blue-black, or deep purple.
Negative (-): Stays yellow-brown (original color of iodine).
 

Examples: Rice, bread, potatoes, and flour instantly turn blue-black.


🥑 D. Lipid/Fat Test (Translucent Paper Test)

Purpose: Checks for oils, fats, and lipids.
Procedure: Rub the food sample onto a piece of unglazed/brown wrapping paper and allow it to dry. Hold it up to a light source.

Result:

Positive (+): The paper leaves a permanent translucent (see-through) spot.
Negative (-): The paper remains opaque once dry.
 

Examples: Butter, cooking oil, peanuts, and avocados.

Quick Reference Summary Table