Edexcel IGCSE Biology · Spec 2.9
Food Tests
The Benedict's, iodine, Biuret and emulsion tests for sugars, starch, protein and fats, and their positive colour changes.
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Food Tests
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Spec 2.9
What you need to know
- Test foods for glucose and starch
- Test foods for protein and fat
- Recall the positive colour change for each test
Active recall
Quick check
Answer each question before opening the answer.
State the reagent and positive result for starch and for protein.
Starch — iodine solution turns blue-black. Protein — Biuret reagent turns from blue to purple.
How do you test for a reducing sugar and for a lipid?
Reducing sugar — Benedict's solution, heat; blue to brick-red. Lipid — ethanol emulsion test; a white/cloudy emulsion forms.
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