Food Test for Fats and Oils

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Food Science and Nutrition

Alternative titles: Ethanol Test for Lipids

Summary

The emulsion test detects fats and oils in food. The sample is first dissolved in ethanol, then mixed with water. A milky-white emulsion indicates the presence of lipids, while a clear solution means none are present.

Procedure

Place the food sample into a test tube with about 2 cm³ of ethanol.
Shake well and let it stand for 2 minutes so lipids can dissolve.
Pour the clear ethanol extract into another test tube containing 2 cm³ of distilled water.
Observe: a cloudy white emulsion shows lipids are present; clear solution means no fats.

Links

Test for Fats - JamJarMMX:

Ethanol Emulsion Test for Fats - A Level Biology - Revisify:

📄 Food test 3 - Emulsion (ethanol) test for Fats - Biology Notes for IGCSE: https://biology-igcse.weebly.com/-food-test-3---emulsion-ethanol-test-for-fats.html

Variations

Compare results from plant oils (e.g., olive oil) and animal fats (e.g., butter).
Test raw vs. cooked food samples.

Safety Precautions

Wear goggles and gloves.
Keep ethanol away from flames—it is highly flammable.
Dispose of test mixtures safely; do not ingest tested samples.

Questions to Consider

Why do lipids form a cloudy emulsion in water? (They are insoluble in water and form tiny droplets that scatter light.)
Why is ethanol used instead of water to dissolve fats? (Lipids are soluble in ethanol but not in water.)
Which foods do you predict will test positive for lipids?