The aim of this investigation is to test for the different types of biological molecules found in different types of food

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Contents Page

Introduction                                                            Page 2

Background Theory                                               Page 3-4

Prediction                                                                Page 4

Materials and methods                                           Page 5

Raw results                                                              Page 6

Analysis of results                                                   Page 6

Evaluation of materials and methods                   Page 6-7

Conclusion                                                               Page 7

References                                                               Page 8

Risk assessment sheet                                             Page 9


Introduction

The aim of this investigation is to test for the different types of biological molecules found in different types of food. We will be testing for starch, proteins, lipids and sugars. We will use nine (9) different types of food samples to test for all the above molecules in each food. When testing for different types of molecules in food, we use different types of food test. These tests are discussed below.

              To test for reducing sugars we will use the Benedict’s test for Reducing Sugars (monosaccharides). Benedict’s reagent is clear blue (from the presence of cupric copper ions, Cu++ ) but when combined and heated to boiling with a substance containing glucose in a chain form, the cupric ions are reduced to a cuprous form (Cu+ ) and then oxidized to form copper oxide (Cu2O). Copper oxide is a brownish-orange substance that is insoluble in water.  Therefore, a positive reaction in a Benedict’s test is the change of the clear light blue solution to an opaque orange-brown solution in a boiling water bath. This colour change indicates the presence of Glucose in a given solution.  

                   To test for the presence of starch, we will use the Starch Test. This is a simple test in which iodine is added to a given solution. If a polysaccharide such as starch is present then the iodine ion will lodge itself in the polysaccharide chain and give it a black-blue colour. If iodine added to a solution turns black-blue than starch is present. If the solution remains the colour of iodine, reddish-orange, there is no starch present.

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To test for Lipids we will use the emulsion this test will indicate the presence of lipids. Lipids are insoluble in water, but soluble in ethanol. To test for lipids, we will add ethanol to a food sample in a test tube then shake vigorously. If lipids are present, the molecules will clump together into tiny droplets spread throughout the liquid; this is called an emulsion.  To test for proteins, we add some Biuret solution to a food sample or solution, a purple colour will indicate the presence of protein.

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