Testing Foods for Reducing Sugars
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: Glucose Test with Benedict’s Solution
Summary
Benedict’s solution is used to test foods for the presence of reducing sugars such as glucose. When heated with a reducing sugar, the blue solution changes to green, yellow, orange, or brick red depending on the sugar concentration.
Procedure
- Place the food sample in a test tube.
- Add a few drops of Benedict’s solution.
- Heat the mixture in a boiling water bath for 2–3 minutes.
- Observe the color change: green/yellow/orange indicates some sugar, while brick red shows a strong positive result.
Links
Biology - Reducing Sugars using Benedict's Reagent Demonstration - Bury College Official:
Benedict's Test for Reducing Sugars - JamJarMMX:
📄 Food test 2 - Benedict's test for Reducing Sugars - Biology Notes for IGCSE: https://biology-igcse.weebly.com/food-test-2---benedicts-test-for-reducing-sugars.html
Variations
- Compare fresh fruit juice to processed drinks.
- Test starchy foods before and after hydrolysis with amylase or acid.
- Quantify results by comparing shades of color to a standard chart.
Safety Precautions
- Use heat-resistant gloves or tongs when handling hot test tubes.
- Avoid direct flame on Benedict’s solution—use a water bath for heating.
- Dispose of test mixtures properly; do not ingest chemicals or tested food.
Questions to Consider
- Why does Benedict’s solution change color when reducing sugars are present? (Copper(II) ions are reduced to copper(I) oxide, which forms a red precipitate.)
- What foods are likely to contain reducing sugars? (Fruits, honey, soft drinks, some vegetables.)
- Why must the mixture be heated for the reaction to work? (Heat provides the energy needed to drive the redox reaction.)