Food tests

AQA 8461 · 4.2.2.1

Four qualitative tests examiners ask for by reagent, colour change and food group. Learn all three parts of each.

Reading mode — read across, know each one cold.

Food group — reagent	Positive result
Starch — iodine solution	orange/brown → blue-blackNo colour change if starch is absent.
Reducing sugars — Benedict's solution (heat in a water bath)	blue → green → yellow → brick-redThe further along the range, the more sugar present.
Proteins — Biuret solution	blue → purple (lilac)Add Biuret A then B; no heating needed.
Lipids — ethanol emulsion test	clear → cloudy white emulsionMix with ethanol, then add to water.

Want this drilled properly?

I tutor GCSE Biology from the mark schemes — recall like this is exactly what the first (free) lesson sorts out.