7/28/2019 Acticity 6.1 Answer

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Date:

Activity 6.1 Nutrient Content in Different Food Samples

Aim To determine the nutrient content in different food samples.

Materials Benedicts solution, dilute hydrochloric acid, sodium bicarbonate powder, starch suspension,Millons reagent, filter paper, distilled water, grape juice, carrot juice, potato, peanuts, bread,cooking oil, boiled egg white and sucrose solution.

Apparatus Test tubes, test tube holder, beaker, measuring cylinder (5 ml), white tile, tripod stand, Bunsenburner, wire gauze, mortar and pestle.

Procedure 1. Carry out food test on various food samples according to the steps listed in the observationcolumn.

Solid foods should be crushed using a mortar and pestle. Then, mix it well withwater to extract the soluble products.

2. Record all your observation.

Method 1. Food tests on various food samples were carried out.2. Observations made were recorded.

Observation Experiment Food sample Observation

A Test for reducing sugar Grape juice A red precipitate is formed

1. Put 1 ml of grape juice and 1 ml of Benedictssolution in a test tube.

2. Heat it in a water bath. Carrot juice A red precipitate is formed

3. Record any change in the mixture. Egg white Clear blue solution

4. Repeat steps 1 to 3 using carrot juice, boiledegg white and sucrose solution.

Sucrosesolution

Clear blue solution

B Test for non-reducing sugar1. Put 1 ml of sucrose solution and a few drops

of dilute hydrochloric acid in a test tube.Sucrosesolution

A red precipitate is formed

2. Heat the mixture in a water bath for 5minutes.

Bread A red precipitate is formed

3. Cool it under running water.

4. Add sodium bicarbonate until there is noeffervescence.

Egg white Clear blue solution

5. Carry out Benedicts test. Record yourobservation.

6. Repeat steps 1 to 5 using bread and eggwhite.

C Test for starch Bread Dark blue colour appears

1. Put a few drops of iodine solution on a pieceof bread. Observe the colour.

Potato Dark blue colour appears

2. Repeat step 1 using potato and groundnut. Groundnut Dark blue colour appears

D Test for protein1. Add a few drops of Millons reagent to

groundnut suspension.Groundnut Brick red coagulate is

formed

2. Heat it in a water bath. Bread White coagulate is formed

3. Observe for any change. Potato White coagulate is formed

4. Repeat steps 1 to 3 using bread, potato andegg white.

Egg white Brick red coagulate isformed

E Test for lipid1. Press a few pieces of crushed groundnut on

to a piece of filter paper.

Groundnut A translucent mark

appears2. Leave the filter paper to dry. Cooking oil A translucent mark appears

3. Hold the filter paper against the light. Notefor a translucent mark.

Grape juice No translucent mark

4. Repeat steps 1 to 3 using cooking oil, grapejuice and crushed potato.

Potato No translucent mark

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Discussion 1. What is the end product obtained when carrying out Benedicts test?

Copper (I) oxide.

2. Explain the chemical process involved in production of the end product mentioned inQuestion 1.

The blue colour of copper (II) sulphate is reduced to red copper (I) oxide by reducing sugar

when carrying out Benedict

s test.

3. To test for non-reducing sugar, why must the food sample be heated with dilutehydrochloric acid?

To hydrolyse non-reducing sugar to reducing sugar.

4. What is the function of sodium bicarbonate in the test for non-reducing sugar?

To neutralise the excess hydrochloric acid.

5. Why must the test for reducing sugar be carried out before testing for non-reducing sugarin any food sample?

To make sure that there is no reducing sugar in the food sample.

Conclusion Different food samples have different nutrient content. Grape juice and carrot juice havereducing sugar while bread and sucrose solution have non-reducing sugar. Egg white hasprotein. Groundnuts have starch, protein and lipid. Potato has starch while cooking oil has lipid.