Food Tests

Test for protein

1. Add biuret reagent (sodium hydroxide + copper (II) sulphate)

2. Positive result = purple / lilac colour (indicating presence of peptide bonds)

Test for non-reducing sugars

1. Do Benedict’s test (as above) and stays blue / negative

2. Heat in a boiling water bath with acid (to hydrolyse into reducing sugars)

3. Neutralise with alkali (eg. sodium bicarbonate)

4. Heat in a boiling water bath with Benedict’s solution

5. Positive result = green / yellow / orange / red precipitate

Test for reducing sugars

1. Add Benedict’s solution (blue) to sample

2.Heat in a boiling water bath

3.Positive result = green / yellow / orange / red precipitate

Test for starch

1. Add iodine dissolved in potassium iodide (orange / brown) and shake / stir

2. Positive result = blue-black

Test for lipids

1. Add ethanol, shake (to dissolve lipids), then add water

2. Positive result = milky white emulsion