Discuss the outcome of your tabulated results and explain why colours changes occurred when a nutrient was found to be present.

In order to determine the identity of the biological molecules in each sample you have performed the appropriate food test as outlined in the Biological Molecules 2.3 Practical Food tests Methods booklet 1.docx.

Each of the samples were tested and the following were observed:

Sample A The Biuret test showed a blue colour. The Emulsion test showed a cloudy white layer. Testing with iodine resulted in the sample being coloured blue black. Testing with Benedict’s reagent the samples appeared orange.

Sample B Testing the sample with iodine the tube appeared yellow in colour. Testing with Benedict’s reagent the sample show no colour change regardless of whether hydrochloric acid/sodium hydrogen were added. The Biuret test showed a purple colour. Testing with absolute alcohol and pouring into cold water gave a clear colour.

Sample C Sample C was first tested with Benedict’s which did not show an initial colour change but when a fresh sample was hydrolysed with HCI (and NaOH added) it gave a green colour. Using Biuret reagent the sample gave a blue colour whilst testing with absolute alcohol followed by addition to cold water gave a milky emulsion. Testing with iodine the sample turned yellow.

Sample D Sample D was tested with iodine with showed a purple colour. When tested with Biuret reagent the sample colour can be described as clear blue. The third test involved mixing the sample with Benedict’s reagent which when heated in a water bath gave a colour resembling brick-red. The final test with sample D, the emulsion test showed that the sample remained clear.

I. Tabulate your results to identify the biologiml molecule content for each sample.

2. Discuss the outcome of your tabulated results and explain why colours changes occurred when a nutrient was found to be present (max 500 words).

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