Edexcel IGCSE Biology 2.9 food tests

Practise food tests by choosing safe methods and interpreting Benedict's, iodine, Biuret and emulsion colour changes in samples.

Exam points

Describe Benedict's, iodine, Biuret or emulsion tests with correct positive colour changes.
Apply food-test results to samples and choose the suitable food or drink from colour evidence.
Control temperature, volume or timing when designing fair food-test practicals.

[Maximum number: 2]

Pineapple juice contains a protease called bromelain.
A student uses this method to investigate the digestion of solid gelatine protein by bromelain.
- place solid gelatine protein into a test tube up to a height of 5 cm
- mix $5 \mathrm{~cm}^{3}$ pineapple juice with $1 \mathrm{~cm}^{3}$ of pH 4 buffer
- place $1 \mathrm{~cm}^{3}$ of the pineapple juice and buffer solution on top of the gelatine
- leave for one hour in a water bath set to $37^{\circ} \mathrm{C}$
- measure the height of the solid gelatine and use it to calculate the volume of gelatine that has been digested

Repeat the method three more times.
The diagram shows part of the student's method.

Figure for Question 2.9 Food tests question 1 — Edexcel IGCSE Biology

Describe how to test for the presence of protein.

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2.9 Food tests question 1